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High plasma levels of atrial natriuretic peptide in preascitic cirrhosis: Indirect evidence of reduced natriuretic effectiveness of the peptide
High Plasma Levels of Atrial Natriuretic Peptide in Preascitic Cirrhosis: Indirect Evidence of Reduced Natriuretic Effectiveness of the Peptide FRANCO TREVISANI,1 ALESSANDRA COLANTONI,1 GIUSEPPE SICA,~ ANTONIO GASBARRINI,1 PAOLA EMANUELAD'INTINO,1 STEFANIA DE NOTARIIS,~ ROSARIA DE JASO,2 ANNARITA BARBIERI,2 ANTONELLO MORSELLI,3 GIOVANNI GASBARRINI,4 AND MAURO BERNARDI~
Controversial results c o m e from spot m e a s u r e m e n t s of plasma atrial natriuretic peptide (ANP) in compensated cirrhotic patients. Moreover, either blunted or exaggerated natriuresis has b e e n described after maneuvers increasing plasma ANP. This does not m a k e it possible to delineate the A N P effectiveness. Plasma ANP, renin activity (PRA) and aldosterone and hematocrit w e r e serially m e a s u r e d (7 AM, 9 AM, 6 PM, and 11 PM) in n i n e preascitic cirrhotic outpatients and in nine h e a l t h y subjects on normal s o d i u m diet (150 mmol/day) and carrying o n their usual activities (mobile from 7 AM to 10 Pro). Daily natriuresis w a s m o n i t o r e d the day before and during the study. In both groups, ANP p e a k e d at the end of the r e c u m b e n c e period (7 AM) and declined on the a s s u m p t i o n of the upright position, so that both ANP values of the standing period w e r e significantly l o w e r than the m e a n daily level. These fluctuations w e r e reciprocal to PRA and hematocrit changes. Patients s h o w e d steadily elevated plasma ANP and r e d u c e d PRA (ANP m e a n daily level: 33.3 -+ 3.8 vs. 15.5 _+ 3.2 pg/mL, P = .004; P R ~ 0.76 _+0.23 vs. 1.66 _+0.21 ng/nd_]hr, P = .003). Aldosterone fluctuations and m e a n daily level w e r e similar in the t w o groups (mean daily level: 122 _+ 11 vs. 119 _+ 9 pg/mL). Natriuresis was well adapted to the s o d i u m intake and similar in healthy subjects (day 1:152 _+ 11 mmol; day 2 : 1 3 8 ~- 12.5 mmol) and patients (143 _+ 15 mmol; 148 _+ 29 retool). Preascitic cirrhotic patients on a normal salt intake and carrying on their usual activities develop a n e w steady state requiring increased ANP levels to maintain a s o d i u m balance. In addition to a red u c e d renal sensitivity to ANP, several subtle abnormalities of the antinatriuretic forces m a y yield the renal h y p o r e s p o n s i v e n e s s to the peptide. (HEPATOLOGY 1995;22:132-137.)
Abbreviations: ANP, atrial natriuretic peptide; PRA, plasma renin activity; Hct, hematocrit. From 1Patologia Speciale Medica I and aClinica Medica I, University of Bologna, 2Laboratorio Centralizzato, S. Orsola Hospital, Bologna, and 4Clinica Medica, Catholic University of Rome, Italy. Received October 6, 1994; accepted February 17, 1995. This study was supported by grants from Ministero dell'Universit~ e della Ricerca Scientifica (Fondi 60% 1994), and from Ricerche in Medicina. Address request reprints to: Franco Trevisani, MD, Patologia Speciale Medica I, via Massarenti 9, 40138 Bologna, Italy. Copyright © 1995 by the American Association for the Study of Liver Diseases. 0270-9139/95/2201-002053.00/0
Atrial natriuretic peptide (ANP) is a physiological regulator of volume homeostasis in h u m a n s through its natriuretic, diuretic, and vasorelaxant properties. 1 A large body of evidence indicates t h a t renal responsiveness to ANP is blunted in patients with cirrhosis and ascites. In fact, elevated plasma ANP coexists with avid sodium retention, and the stimulation of the peptide secretion by means of physiological maneuvers or its infusion elicits subnormal increases in natriuresis in most cases. 2'a Although an increased density of C(clearance)-receptors of ANP in the kidney may contribute to the reduced ANP effectiveness,4 this has been chiefly attributed to the presence of activated antinatriuretic forces, i.e., renin-angiotensin-aldosterone axis and sympathoadrenergic tone. 5.s In preascitic cirrhosis, both plasma levels and renal effectiveness of ANP are a subject of controversy. Either normal 9-1a or tendentially 14-~7 or significantly increased ~s2° plasma concentrations of ANP have been reported. Similarly, either blunted 14'19'2. or exaggerated 22 natriuresis has been found to follow plasma ANP elevation. There are no studies investigating ANP plasma levels at different clock times and the relationship between the daily ANP profile and sodium balance in preascitic cirrhotic patients maintained on normal salt intake and carrying on their usual activities. The current investigation aimed to assess the daily behavior of plasma ANP and the relationship between plasma ANP and renal sodium handling in preascitic cirrhotic patients carrying on their normal life. Therefore, plasma ANP level was serially measured during the day along with plasma renin activity (PRA) and hematocrit (Hct), assumed as markers of variations in effective volemia 2a and blood volume, respectively. Plasma aldosterone concentration and daily renal sodium excretion were also assessed. PATIENTS AND METHODS
Nine ambulatory patients (eight men and one woman, aged from 32 to 70 years, mean 57.8 _+4.3 years) with histologically proven cirrhosis (all belonging to Pugh-Child class A24) were recruited. Cirrhosis was caused by hepatitis B or C virus infection in six cases and by C virus infection plus alcohol abuse in the remainder. All patients had abstained from
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TABLE 1. C l i n i c a l a n d L a b o r a t o r y C h a r a c t e r i s t i c s of C i r r h o t i c P a t i e n t s Patient
Albumin (mg/dL)
PA (%)
Bilirubin (mg/dL)
GFR (mL/min)
I-Ib (g/dL)
GEC (mg/kg/min)
HE (grade)
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3.1 4.2 3.6 3.0 3.7 3.8 4.2 3.5 2.8
62 75 62 55 60 55 65 69 70
1.7 1.1 1.0 1.0 1.5 1.3 1.5 0.7 0.7
158 101 160 176 140 204 118 133 106
11.3 15.6 14.3 15.6 11.0 12.7 13.3 13.3 12.5
5.13 4.92 5.50 4.82 5.98 4.99 4.90 4.09 5.22
0 0 0 0 0 0 0 0
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Abbreviations: PA, prothombin activity (normal value: ->80%); GFR, glomerular filtration rate (measured as creatinine clearance); Hb, hemoglobin; GEC, galactose elimination capacity (normal value: >6 mg/kg/min); HE, hepatic encephalopathy.
d r i n k i n g for at l e a s t 1 y e a r before enrollment. Exclusion criter i a were cardiac, renal, r e s p i r a t o r y , neurologic or metabolic diseases, r e c e n t (within 4 months) g a s t r o i n t e s t i n a l hemorrhage, a n d history of previous ascites or diuretic t r e a t m e n t . The absence of ascites was confirmed by u l t r a s o n o g r a p h y . P o r t a l h y p e r t e n s i o n was a s c e r t a i n e d by the finding of a n enl a r g e d portal vein a t u l t r a s o n o g r a p h y or esophageal varices at endoscopy. Table I reports t h e m a i n clinical a n d l a b o r a t o r y f e a t u r e s of t h e patients. Only one was on drugs influencing the p a r a m e t e r s u n d e r study. I n this patient, t r e a t e d w i t h propranolol to p r e v e n t variceal rebleeding, the d r u g was stopped 10 days before entry. Nine h e a l t h y male volunteers, comparable for age (26 to 65 years, m e a n 54.2 _+ 2.6 years, P = .23), were enrolled as a control group. All the subjects ate a diet providing 150 m m o l / d a y of sodium for 5 days before a n d d u r i n g the study. They were a d m i t t e d to t h e hospital at 9 PM of the fifth day, a n d r e m a i n e d in bed from 10 PM to 7 AM in a single, quiet, d a r k e n e d room. Thereafter, t h e y were i n s t r u c t e d to leave the hospital, c a r r y on t h e i r n o r m a l activities (office or l a b o r a t o r y work), a n d r e t u r n to t h e h o s p i t a l for blood sampling. Meals were t a k e n a t 8 AM, 1 PM, and 8 PM. Blood s a m p l e s were collected at 11 PM a n d 7 AM (in supine subjects), 9 AM a n d 6 PM (in mobile subjects) t h r o u g h a heparinized catheter; before t h e l a s t two s a m p l i n g s were t a k e n , the subjects h a d been s e a t e d for 30 minutes. Blood was collected to d e t e r m i n e creatinine, sodium, ANP, a n d aldosterone concentrations, p l a s m a r e n i n activity a n d h e m a t o c r i t (Hct). To m e a s u r e r e n a l sodium excretion (UNaV), 24-hour u r i n e collections were performed s t a r t i n g from 10 PM both the day before a n d t h e d a y of the study. On the d a y of the experiment, c r e a t i n i n e excretion was also m e a s u r e d . Informed consent was o b t a i n e d from each p a r t i c i p a n t , a n d the s t u d y protocol was designed according to the principles of the Declaration of H e l s i n k i and approved by the Senior Staff C o m m i t t e e of our d e p a r t m e n t . Assays. Blood s a m p l i n g and a s s a y m e t h o d s for ANP, PRA, a n d aldosterone have been r e p o r t e d in detail elsewhere. 13'2°'2~ All s a m p l e s were a s s a y e d in a single run. Hct was d e t e r m i n e d by Technicon H2 (Technicon I n s t r u m e n t s Corporation, Tarrytown, NY). U r i n a r y a n d p l a s m a sodium concentrations were d e t e r m i n e d by selective ion electrodes and creatinine by a l k a l i n e picrate m e t h o d (Olympus A U 5000, Olympus Ltd, Tokyo, J a p a n ) . F i l t e r e d load of sodium was calculated as: FN~ = N a × GFR, where N a is the average value of the p l a s m a sodium concentrations m e a s u r e d t h r o u g h o u t t h e d a y a n d G F R is the g l o m e r u ] a r filtration r a t e (clearance of creatinine). Statistical Analysis. Results were expressed as m e a n _+ SEM. The v a r i a b l e d i s t r i b u t i o n was a s s e s s e d by Kolmo-
gorov-Smirnov n o r m a l i t y test, a n d logarithmic t r a n s f o r m a tion of the non-normally d i s t r i b u t e d p a r a m e t e r s was made. S t a t i s t i c a l significance of the changes observed within a n d between groups was e v a l u a t e d by m e a n s ofANOVA. Comparisons b e t w e e n r e p e a t e d m e a s u r e s were m a d e by m e a n s of ANOVA for r e p e a t e d m e a s u r e s . Correlation coefficients were derived by l i n e a r regression analysis. RESULTS
Plasma ANP significantly changed throughout the d a y i n b o t h c o n t r o l s u b j e c t s ( P = .001) a n d p a t i e n t s ( P < .001). T h e d a i l y p r o f i l e p a r a l l e l e d i n t h e t w o g r o u p s : A N P p e a k e d a t t h e e n d o f t h e s u p i n e p e r i o d (7 AM) a n d declined with the assumption of the upright posture. T h u s b o t h t h e 9 AM a n d 6 PM v a l u e s w e r e l o w e r t h a n those seen in the recumbence period and the mean d a i l y l e v e l (Fig. 1). D u r i n g t h e u p r i g h t p o s i t i o n , A N P declined only in the control group. At every sampling time, ANP of patients was signifi-
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CLOCK TIME ( h ) FIG. 1. Time course of plasma atrial natriuretic peptide concentration (ANP) during the 24 hours of the experiment. The arrow indicates the change of posture. The reported P value refers to the comparison between healthy and cirrhotic subjects (ANOVA for repeated measures), op <_ .033 with respect to the mean daily level, *P -< .049 vs. the supine values, §P = .002 vs. the 7:00 value, #P = .017 vs. the 9:00 value. - - • - - , controls; - - [] - - , patients with cirrhosis.
134
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HEPATOLOGY July 1995
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CLOCK TIME ( h ) FIG. 2. Time course of plasma renin activity (PRA) and hematocrit (HCT) during the 24 hours of the experiment. The arrow indicates the change of posture. The reported P value refers to the comparison between healthy and cirrhotic subjects (ANOVA for repeated measures), o p < .021 vs. mean daily level, *P -< .047 vs. the supine values, #P -< .014 vs. the 9:00 value, " P = .003 vs, the 23:00 value. - - • - - , controls; - - [] - - , patients with cirrhosis.
cantly elevated as compared with h e a l t h y controls (P = .01 or lower), so t h a t the mean daily level was significantly higher in the former (33.3 _+ 3.8 vs. 15.5 _+ 3.2 pg/mL, P = .004). Daily PRA changes were statistically significant (control subjects: P < .001; patients: P = .002) and ran in parallel in the two groups (Fig. 2). The PRA behavior was reciprocal to t h a t of ANP: it peaked at 9 AM and reached the lowest value at the end of the supine period. In both groups, the PRA levels seen in the upright position were significantly higher t h a n those found during recumbence. Throughout the study, PRA was significantly lower in patients t h a n in healthy volunteers (P = .019 or lower). Consequently, the PRA mean daily level was significantly lower in patients (0.76 +_ 0.23 vs. 1.66 _+ 0.21 ng/mL/h, P = .003). During the 24 hours of the experiment Hct fluctuated significantly in both the control (P = .001) and the
patient (P < .001) groups (Fig. 2). The daily profile paralleled t h a t of PRA: peak values were observed at 9 AM, and this value was significantly higher t h a n the supine values in both groups. Over the standing period, Hct declined in both healthy and cirrhotic subjects, so t h a t the value at 6 PM was significantly lower t h a n at 9 AM. At any given time, Hct was lower in patients t h a n in healthy controls (P = .003 or lower). Plasma aldosterone changes during the day were statistically significant in both groups (control subjects: P < .001; patients: P < .001). The zenith value occurred in the morning. With the exception of the 11 PM value, which was higher in patients (89 + 10 vs. 55 __ 5 pg/ mL, P -- .004), the time-related values did not differ in the two groups (7 AM: 158 _+ 18 vs. 155 _+ 22 pg/mL, P = .85; 9 AM: 166 _+ 16 vs. 155 _+ 14 pg/mL, P = .63; 6 PM: 96 _+ 11 vs. 88 _ 10 pg/mL, P = .62). The mean daily level was similar in cirrhotic and healthy subjects (122 _+ 11 vs. 119 _+ 9 pg/mL, P = .82). The ratios between mean daily levels of ANP and aldosterone (ANP/aldosterone: 0.29 _+ 0.05 vs. 0.14 _+ 0.03, P = .012) and between mean daily levels of ANP and PRA (ANP/PRA: 67 _+ 14 vs. 12 _+ 3, P < .001) were higher in the cirrhotic group. FNa did not differ between healthy subjects and cirrhotic patients (17.1 _+ 1.4 vs. 20.4 _+ 1.7 mmol/min, P = .69). The day before and during the experiment, daily UNaV was well adapted to the intake and did not change either in control subjects (day 1:152 _+ 11 mmol; day 2:138 _+ 12.5 mmol, P = .14) or in patients (day 1:143 _+ 15 mmol; day 2:148 _+ 29 mmol, P = .49) (Fig. 3). No statistically significant differences were found between the two groups (day 1: P = .55, day 2: P = .53). Finally, body weight remained steady in both groups (Fig. 3). Mean arterial pressure of controls and cirrhotic did not differ at any given time (11 PM: 95 _+ 4 vs. 94 _+ 3 m m H g , P = . 7 6 ; 7 A M : 9 0 + 6 v s . 98_+ 3 m m H g , P
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FIG. 3. Body weight (lines) and daily renal excretion of sodium (bars). Note t h a t the daily sodium intake was 150 mmol. Dashed bars: healthy subjects, solid bars: cirrhotic patients. Day 1: day before the experiment, day 2: day of the experiment. - - • - - , controls; - - [] - - , patients with cirrhosis.
HEPATOLOGYVol. 22, No. 1, 1995
TREVISANI ET AL 135
the depressed PRA levels seen in our patients, along with the results of many other studies employing different protocols and techniques and analyzing compensated patients selectively, 13'15'3~ are consistent with a condition of central volume expansion. The resetting at persistently elevated ANP plasma levels did not affect the intrinsic surge toward the zenith but was able to abrogate the fall to the nadir. This finding is in line with the weakened rhythmicity of ANP secretion documented in compensated patients maintained supine 37 and could be again an effect of an increased central volemia. The daily renal excretion of sodium of our cirrhotic patients was well balanced to the intake and similar to that of healthy individuals. This finding attests that, even if the patients had previously developed a renal fluid retention responsible for the increased blood volDISCUSSION ume, they reached a new steady state. It is also worth In supine compensated cirrhotic patients, spot mea- noting that the expansion of total and central blood surements of plasma ANP have provided conflicting volume and the elevation of ANP cannot be prevented results. 912'152° Two studies dealing with sitting or by low-sodium diet (20 mmol/day). 36 From the precedstanding patients have found normal or insignificantly ing it can be inferred that, at various salt intakes, inincreased ANP levels. ~'14 This heterogeneous picture creased ANP levels are an adaptive mechanism needed may be attributable to differences in the patient selec- to maintain the sodium balance. As in experimental tion and experimental protocol among the studies. 26 cirrhosis, 3s in preascitic h u m a n cirrhosis some mechaThe current study first evaluated plasma ANP concen- nisms favoring salt retention would hinder a full-blown tration at different clock times in preascitic cirrhotic renal response to the peptide. The results of ANP infupatients on normal sodium diet and carrying on their sion or stimulation of its secretion provide further eviusual activities. It clearly demonstrated that, in this dence of this. The bolus administration of synthetic acondition, patients maintained higher ANP levels than human-ANP induced a lower natriuretic response in healthy subjects, regardless of time of day and posture. patients without or with minimal ascites than in norDespite a resetting of plasma ANP at a higher level, mal subjects. 19'21 However, the abnormal blood presthe daily profile of the peptide values was near normal. sure fall experienced by patients in these experiments Because atrial distension is the main stimulus for ANP likely contributed to their blunted natriuretic response. release, 1 variations of posture, which prompt blood vol- More intriguing, 1-hour head-out water immersion ume redistribution between the central and peripheral evoked a reduced natrinresis despite a normal ANP area, 13 would be expected to be crucial in setting circu- increase, ~4 and normal supine-induced natriuresis was lating ANP levels. Consistently, the postural change achieved thanks to an exaggerated ANP secretion. 39 likely accounted for the prominent variations of plasma Finally, the hypernatriuresis induced by 3 hours' water ANP seen in both healthy controls and patients. In fact, immersion was coupled with an elevation of plasma the decline of ANP concentration closely coincided with ANP far greater in patients than in healthy controls the assumption of the upright position and the eleva- and disproportionate to the magnitude of the achieved tion of PRA (a marker of effective volemia 2~) and Hct, natriuresis. 22 which reflects the gravity-induced extravascular shift Because the presence of either abnormal precursors of protein-free fluid in the dependent body regionsY In or structurally defective ANP has been ruled out in addition to the volume-induced changes, the intrinsic cirrhosis, 4° a renal hyporesponsiveness to the peptide rhythmicity of ANP secretion 2s'29 probably contributed could be inferred. Contrary to what happens in sodiumin setting its plasma levels in both groups. In fact, ANP retaining patients, 5'~'s'1~ the elevation of ANP in preof patients peaked in the morning as in the control ascitic cirrhosis cannot be attributed to the need of counteracting increased levels of angiotensin II or aldogroup. The mechanism(s) responsible for the ANP increase sterone. In fact, according to several previous reports, 4~ in cirrhosis have not been definitively settled. Although PRA of our patients was reduced and plasma aldostea contribution by a reduced clearance cannot be ex- rone only transiently increased, so that its mean daily cluded, ~° it is likely that the ANP augmentation is level was equal in the two groups. The coexistence of mainly due to hypersecretion. 3~'~2The increased release normal plasma aldosterone along with depressed PRA from atria would be eventually caused by the expansion could be attributed to either increased adrenal sensitivof total and central plasma v o l u m e . 3'15'17'3~'34 Such an ity to angiotensin I142 or impaired hepatic metabolism assumption is not supported by the findings by Henrik- of the hormone. 41'48 sen et al, 3~ who found reduced central blood volume in Sympathetic nervous system hypertone has been cirrhosis with first-pass clearance technique. However, claimed to contribute to renal sodium retention in cir-
= .29; 9 AM: 87 _+ 4 vs. 95 +_ 3 mm Hg, P -- .14; 6 PM: 90 +_ 3 vs. 93 _+ 3 pg/mL, P = .53). As a result, the mean daily levels were similar (91 ± 4 vs. 95 _+ 3, P = .40). Time-related and mean daily values of heart rate were also similar in the two groups (11 PM: 72 ± 3 vs. 7 4 ± 3 b p m , P = .71; 7 AM: 69 +__2 vs. 68 ± 2 b p m , P = .76; 9 AM: 71 ± 3 vs. 71 ± 2 bpm, P = .78; 6 PM: 71 ± 3 vs. 71 ± 2 bpm, P = .97; mean daily value: 71 ± 2 vs. 71 ± 2, P = .96). The correlations between UN~V and ANP, aldosterone, ANP/aldosterone, and ANP/PRA were assessed. Weak relationships were found between UNaV and mean daily plasma levels o f A N P (r = .64, P = .058) in healthy subjects, and between UNaV and log ANP/PRA (r = .66, P = .052) in patients.
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TREVISANI ET AL
rhosis, t5 However, in agreement with many antecedent studies, 1°'~7'2°'4°'46 plasma norepinephrine concentrat i o n - i n d e x of sympathetic activity--of our patients was not elevated (unpublished observations). Our data also excluded that ANP hypoeffectiveness was caused by a manifest impaired renal perfusion, because the hemodynamic pattern (mean arterial pressure and heart rate), glomerular filtration rate, and filtered load of sodium did not differ between patients and controls. However, the relationship between ANP/ PRA and sodium excretion observed in the patient group could reflect the critical dependence of renal sodium handling from effective volemia in cirrhosis. The actual reasons for the blunted natriuretic response to ANP in preascitic cirrhosis cannot be deduced from the current study. However, it could be hypothesized that this defect results from the cooperation of several subtle abnormalities such as (1) tubular hypersensitivity to aldosterone33'46; (2) increased density of C(clearance)-receptors of ANP in the kidney (so far described only in cirrhotic rats with ascites4), or defective second messenger production. In this respect, it is worth noting that the ANP-induced cyclic guanosine monophosphate generation by isolated glomeruli is slightly reduced in preascitic experimental cirrhosis, 32 and an insufficient cGMP generation despite normal increase of plasma ANP has been claimed to be responsible for the inability to escape from the salt-retaining effect of fludrocortisone by compensated patientsY However, the results of Skorecki et al 5 did not confirm the defective cGMP generation even in sodium-retaining cirrhosis; (3) slight increase in proximal tubular reabsorption of sodium, 4s which diminishes sodium delivery to the collecting duct, site of ANP action. In conclusion, the current study clearly showed that preascitic cirrhotic patients on normal sodium diet and engaged in their usual activities have steadily increased plasma ANP. Despite this, renal sodium excretion was not greater than in normal subjects, and it was well adapted to the intake. The blunted natriuretic action of ANP cannot be attributed to the activation of the renin-angiotensin-aldosterone and sympathoadrenergic systems. However, the presence of other mechanism(s) promoting a subtle trend to renal sodium retention and opposing the ANP effects cannot be excluded. This defect could be involved in the pathogenesis of the deranged renal sodium handling that in preascitic patients becomes manifest only under sodium load 49'5° and mineralocorticoid administration. 47'51 REFERENCES 1. Goetz KL. Physiology and pathophysiology of atrial peptides. Am J Physiol 1988;254:El-El5. 2. Warner L, Skorecki K, Blendis LM, Epstein M. Atrial natriuretic factor and liver disease. HEPATOLOGY1993; 17:500-513. 3. Wong F, Blendis LM. Pathophysiology of sodium retention and ascites formation in cirrhosis: role of atrial natriuretic factor. Semin Liver Dis 1994; 14:59-70. 4. Gerbes AL, Kollenda MC, VoUmar AM, Reichen J, Vakil N, Scarborough RM. Altered density of glomerular binding sites for atrial natriuretic factor in bile duct-ligated rats with ascites. HEPATOLOGY 1991; 13:562-566.
HEPATOLOGYJuly 1995 5. Skorecki KL, Leung WM, Campbell P, Warner LC, Wong PY, Bull S, Logan A, et al. Role of atrial natriuretic peptide in the natriuretic response to central volume expansion induced by head-out water immersion in sodium-retaining cirrhotic subjects. Am J Med 1988;85:375-382. 6. Epstein M. Atrial natriuretic factor in patients with liver disease. Am J Nephrol 1989;9:89-100. 7. Gin,s P, Tit6 L, Arroyo V, Llach J, Salmer6n JM, Gin6s A, Jim6nez W, et al. Renal insensitivity to atrial natriuretic peptide in patients with cirrhosis and ascites. Effect of increasing systemic arterial pressure. Gastroenterology 1992; 102:280-286. 8. Tobe SW, Blendis LM, Morali GA, Warner LC, Logan AG, Skorecki KL. Angiotensin II modulates atrial natriuretic factor-induced natriuresis in cirrhosis with ascites. Am J Kidney Dis 1993;21:472-479. 9. Bonkovsky H, Hartle D, Simon D, Mellen B, Kutner M, Galambos J. Decreased plasma atrial natriuretic peptide in cirrhotic ascitic patients [Abstract]. HEPATOLOGY1986;6:1213. 10. Burghardt W, Wernze H, Diehl KL. Atrial natriuretic peptide in hepatic cirrhosis: relation to stage of disease, sympathoadrenal system and renin-aldosterone axis. Klin Wochenschr 1986;64 (suppl VI):103-107. 11. Epstein M, Loutzenhiser R, Norsk P, Atlas S. Relationship between plasma ANF responsiveness and renal sodium handling in cirrhotic humans. Am J Nephron 1989;9:133-143. 12. Tesar V, Horky K, Petryl J, Kozakova M, Gregorova I, Brodanova M, Kordac V, et al. Atrial natriuretic factor in liver cirrhosis: the influence of volume expansion. Horm Metab Res 1989;21: 519-522. 13. Bernardi M, Di Marco C, Trevisani F, De Collibus C, Fornal6 L, Baraldini M, Andreone P, et al. The hemodynamic status of preascitic cirrhosis: an evaluation under steady-state conditions and after postural changes. HEPATOLOGY1992; 16:341-346. 14. Gerbes AL, Wernze H, Arendt RM, Riedel A, Sauerbruch T, Paumgartner G. Atrial natriuretic factor and renin-aldosterone in volume regulation of patients with cirrhosis. HEPATOLOGY 1989;9:417-422. 15. Rector WG, Adair O, Hossack KF, Rainguet S. Atrial volume in cirrhosis: relationship to blood volume and plasma concentration of atrial natriuretic factor. Gastroenterology 1990;99:766-770. 16. Warner L, Skorecki K, Blendis LM, Epstein M. The response of natrial factor and sodium excretion to dietary sodium challenges in patients with chronic liver disease. HEPATOLOGY1990; 12:460466. 17. Wong F, Liu P, Tobe S, Morali G, Blendis LM. Central blood volume in cirrhosis: measurement with radionuclide angiography. HEPATOLOGY1994; 19:312-321. 18. Vinel JP, Denoyel P, Viossat I, Cales P, Caucanas JP, Chabrier PE, Esquerre JP, et al. Atrial natriuretic peptide, plasma renin activity, plasma volume, systemic vascular resistance and cardiac output in patients with cirrhosis. J Gastroenterol Hepatol 1989;4:529-535. 19. Beutler JJ, Koomans HA, Rabelink TJ, Gaillard CA, Van Hatturn J, Boer P, Mees EJD. Blunted natriuretic response and low blood pressure after atrial natriuretic factor in early cirrhosis. HEPATOLOGY1989; 10:148-153. 20. Trevisani F, Bernardi M, Gasbarrini A, Tam6 MR, Giancane S, Andreone P, Baraldini M, et al. Bed rest-induced hypernatriuresis in cirrhotic patients without ascites: does it contribute to maintain "compensation"? J Hepatol 1992; 16:190-196. 21. Salerno F, Badalamenti S, Incerti P, Capozza L, Mainardi L. Renal response to atrial natriuretic peptide in patients with advanced liver cirrhosis. HEPATOLOGY1988;8:21-26. 22. Campbell PJ, Leung WM, Logan AG, Debowski TE, Blendis LM, Skorecki KL. Hyperresponsiveness to water immersion in sodium retaining cirrhotics: the role of atrial natriuretic factor. Clin Invest Med 1988; 11:392-395. 23. Rector WJ, Hossack KF. Pathogenesis of sodium retention complicating cirrhosis: is there room for diminished "effective" arterial blood volume? Gastroenterology 1988;95:1658-1663. 24. Pugh RHN, Murray-Lyon IM, Dawson JL, Pietroni MC, Williams R. Transection of oesophagus for bleeding oesophageal varices. Br J Surg 1973;60:646-649.
HEPATOLOGYVol. 22, No. 1, 1995 25. Bernardi M, De Palma R, Trevisani F, Malatesta R, Baraldini M, Cursaro C, Gasbarrini G. Unaltered dopaminergic modulation of aldosterone secretion in cirrhosis. Clin Sci 1988; 74:137-143. 26. Gerbes AL. The role of atrial natriuretic peptide (ANP) in chronic liver disease. Pharmacol Ther 1993; 58:381-390. 27. Davies R, Slater JDH, Forsling ML, Payne N. The response of arginine vasopressin and plasma renin activity to postural changes in normal man, with observations on syncope. Clin Sci Mol Med 1976;51:267-274. 28. Donckier J, Anderson JV, Yeo T, Bloom SR. Diurnal rhythm in the plasma concentration of atria] natriuretic peptide. N Engl J Med 1985;315:710-711. 29. Richards AM, Tonolo G, Fraser R, Morton JJ, Leckie BJ, Ball SG, Robertson JIS. Diurnal change in plasma natriuretic peptide concentrations. Clin Sci 1987;73:489-495. 30. Moreau R, Pussard E, Brenard R, Gaudin C, Berdeaux A, Lebrec D. Clearance of atrial natriuretic peptide in patients with cirrhosis: role of liver failure. J Hepatol 1991;13:351-357. 31. Gin,s P, Jim~nez W, Arroyo V, Navasa M, LSpez C, Tit5 L, Serra A, et al. Atrial natriuretic factor in cirrhosis with ascites: plasma levels, cardiac release and splanchnic extraction. HEPATOLOGY 1988;8:636-642. 32. Morgan TR, Morgan K, Jonas GM, Thillainadarajah I. Atrial natriuretic factor in experimental cirrhosis in rats. Gastroenterology 1992; 102:1356-1362. 33. Bernardi M, Trevisani F, Santini C, De Palma R, Gasbarrini G. Aldosterone related blood volume expansion in cirrhosis before and during the early phase of ascites formation. Gut 1983;24:761-766. 34. Lieberman FL, Reynolds TB. Plasma volume in cirrhosis of the liver: its relation to portal hypertension, ascites, and renal failure. J Clin Invest 1967;46:1297-1308. 35. Henriksen JH, Bendtsen F, Sorensen TIA, Stadeager C, RingLarsen H. Reduced central blood volume in cirrhosis. Gastroenterology 1989; 97:1506-1513. 36. Wong F, Liu P, Allidina Y, Blendis LM. Pattern of sodium handling and its consequences in pre-ascitic cirrhosis [Abstract]. Gastroenterology 1995; in press. 37. Colantonio D, Pasqualetti P, Casale R, Desiati P, Giandomenico G, Natali G. Atrial natriuretic peptide-renin-aldosterone system in cirrhosis of the liver: circadian study. Life Sci 1989;45:631635. 38. Olivera A, Gutkowska J, Rodriguez-Puyol D, Fernandez-Cruz A, Lopez-Novoa JM. Atrial natriuretic peptide in rats with experimental cirrhosis of the liver without ascites. Endocrinology 1988; 122:840-846. 39. Bernardi M, Di Marco C, Trevisani F, Fornal6 L, Andreone P,
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41. 42.
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48.
49. 50.
51.
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Cursaro C, Baraldini M, et al. Renal sodium retention during upright posture in preascitic cirrhosis. Gastroenterology 1993; 105:188-193. Jimenez W, Gutkowska J, Gines P, Arroyo V, Rivera F, Rodes J. Molecular form and biological activity of atrial natriuretic factor in patients with cirrhosis and ascites. HEPATOLOGY 1991; 14:601~607. Bernardi M, Trevisani F, Gasbarrini A, Gasbarrini G. Hepatorenal disorders: role of the renin-angiotensin-aldosteronesystem. Semin Liver Dis 1994; 14:23-34. Bernardi M, De Palma R, Trevisani F, Santini C, Capani F, Baraldini M, Gasbarrini G. Chronobiological study of factors affecting plasma aldosterone concentration in cirrhosis. Gastroenterology 1986;91:683-691. Bernardi M, Trevisani F, Gasbarrini A, Gasbarrini G. Degradation of circulating cortical steroids: physiology and pathophysiology. In: Henriksen JH~ ed. Degradation of bioactive substances: physiology and pathophysiology. Boca Raton, FL: CRC Press, 1991:267-288. Bichet DG, Van Putten VJ, Schrier RW. Potential role of sympathetic activity in impaired sodium and water excretion in cirrhosis. N Engl J Med 1982;307:1552-1557. Bernardi M, Trevisani F, De Palma R, Ligabue A, Capani F, Baraldini M, Gasbarrini G. Chronobiological evaluation of sympathoadrenergic function in cirrhosis: relationship with arterial pressure and heart rate. Gastroenterology 1987;93:1178-1186. Bernardi M, Trevisani F, Gasbarrini G. The renin-angiotensinaldosterone system in liver disease. In: Bonzom A, Blendis LM, eds. Cardiovascular complications of liver disease. Boca Raton, FL: CRC Press, 1990:29-62. Tesar V, Spicak J, Horky K, Zabra J, Widimsky J, Jedlicka J, Marecek Z. Renal resistance to atrial natriuretic factor as a cause of the escape failure phenomenon in patients with non-ascitic liver cirrhosis. Cas Lek Cesk 1994; 133:111-115. LSpez-Novoa JM, Rengel MA, Rodicio JL, Hernando L. A micropuncture study of sodium and water retention in rats with experimental cirrhosis of the liver. Am J Physio11977; 232:F315-F318. VIA Naccarato R, Messa P, D'Angelo A, Fabris A, Messa M, Chiaramonte M, Gregolin C, et al. Renal handling of sodium and water in early chronic liver disease. Gastroenterology 1981; 81:205-210. Caregaro L, Lauro S, Angeli P, Merkel C, Gatta A. Renal water and sodium handling in compensated liver cirrhosis: mechanism of impaired natriuresis after saline loading. Eur J Clin Invest 1985; 15:30-34. Wilkinson SP, Smith IK, Moodie H, Poston L, Williams R. Studies on mineralocorticoid "escape" in cirrhosis. Clin Sci 1979;56:401-406.
Controversial results c o m e from spot m e a s u r e m e n t s of plasma atrial natriuretic peptide (ANP) in compensated cirrhotic patients. Moreover, either blunted or exaggerated natriuresis has b e e n described after maneuvers increasing plasma ANP. This does not m a k e it possible to delineate the A N P effectiveness. Plasma ANP, renin activity (PRA) and aldosterone and hematocrit w e r e serially m e a s u r e d (7 AM, 9 AM, 6 PM, and 11 PM) in n i n e preascitic cirrhotic outpatients and in nine h e a l t h y subjects on normal s o d i u m diet (150 mmol/day) and carrying o n their usual activities (mobile from 7 AM to 10 Pro). Daily natriuresis w a s m o n i t o r e d the day before and during the study. In both groups, ANP p e a k e d at the end of the r e c u m b e n c e period (7 AM) and declined on the a s s u m p t i o n of the upright position, so that both ANP values of the standing period w e r e significantly l o w e r than the m e a n daily level. These fluctuations w e r e reciprocal to PRA and hematocrit changes. Patients s h o w e d steadily elevated plasma ANP and r e d u c e d PRA (ANP m e a n daily level: 33.3 -+ 3.8 vs. 15.5 _+ 3.2 pg/mL, P = .004; P R ~ 0.76 _+0.23 vs. 1.66 _+0.21 ng/nd_]hr, P = .003). Aldosterone fluctuations and m e a n daily level w e r e similar in the t w o groups (mean daily level: 122 _+ 11 vs. 119 _+ 9 pg/mL). Natriuresis was well adapted to the s o d i u m intake and similar in healthy subjects (day 1:152 _+ 11 mmol; day 2 : 1 3 8 ~- 12.5 mmol) and patients (143 _+ 15 mmol; 148 _+ 29 retool). Preascitic cirrhotic patients on a normal salt intake and carrying on their usual activities develop a n e w steady state requiring increased ANP levels to maintain a s o d i u m balance. In addition to a red u c e d renal sensitivity to ANP, several subtle abnormalities of the antinatriuretic forces m a y yield the renal h y p o r e s p o n s i v e n e s s to the peptide. (HEPATOLOGY 1995;22:132-137.)
Abbreviations: ANP, atrial natriuretic peptide; PRA, plasma renin activity; Hct, hematocrit. From 1Patologia Speciale Medica I and aClinica Medica I, University of Bologna, 2Laboratorio Centralizzato, S. Orsola Hospital, Bologna, and 4Clinica Medica, Catholic University of Rome, Italy. Received October 6, 1994; accepted February 17, 1995. This study was supported by grants from Ministero dell'Universit~ e della Ricerca Scientifica (Fondi 60% 1994), and from Ricerche in Medicina. Address request reprints to: Franco Trevisani, MD, Patologia Speciale Medica I, via Massarenti 9, 40138 Bologna, Italy. Copyright © 1995 by the American Association for the Study of Liver Diseases. 0270-9139/95/2201-002053.00/0
Atrial natriuretic peptide (ANP) is a physiological regulator of volume homeostasis in h u m a n s through its natriuretic, diuretic, and vasorelaxant properties. 1 A large body of evidence indicates t h a t renal responsiveness to ANP is blunted in patients with cirrhosis and ascites. In fact, elevated plasma ANP coexists with avid sodium retention, and the stimulation of the peptide secretion by means of physiological maneuvers or its infusion elicits subnormal increases in natriuresis in most cases. 2'a Although an increased density of C(clearance)-receptors of ANP in the kidney may contribute to the reduced ANP effectiveness,4 this has been chiefly attributed to the presence of activated antinatriuretic forces, i.e., renin-angiotensin-aldosterone axis and sympathoadrenergic tone. 5.s In preascitic cirrhosis, both plasma levels and renal effectiveness of ANP are a subject of controversy. Either normal 9-1a or tendentially 14-~7 or significantly increased ~s2° plasma concentrations of ANP have been reported. Similarly, either blunted 14'19'2. or exaggerated 22 natriuresis has been found to follow plasma ANP elevation. There are no studies investigating ANP plasma levels at different clock times and the relationship between the daily ANP profile and sodium balance in preascitic cirrhotic patients maintained on normal salt intake and carrying on their usual activities. The current investigation aimed to assess the daily behavior of plasma ANP and the relationship between plasma ANP and renal sodium handling in preascitic cirrhotic patients carrying on their normal life. Therefore, plasma ANP level was serially measured during the day along with plasma renin activity (PRA) and hematocrit (Hct), assumed as markers of variations in effective volemia 2a and blood volume, respectively. Plasma aldosterone concentration and daily renal sodium excretion were also assessed. PATIENTS AND METHODS
Nine ambulatory patients (eight men and one woman, aged from 32 to 70 years, mean 57.8 _+4.3 years) with histologically proven cirrhosis (all belonging to Pugh-Child class A24) were recruited. Cirrhosis was caused by hepatitis B or C virus infection in six cases and by C virus infection plus alcohol abuse in the remainder. All patients had abstained from
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TABLE 1. C l i n i c a l a n d L a b o r a t o r y C h a r a c t e r i s t i c s of C i r r h o t i c P a t i e n t s Patient
Albumin (mg/dL)
PA (%)
Bilirubin (mg/dL)
GFR (mL/min)
I-Ib (g/dL)
GEC (mg/kg/min)
HE (grade)
1
3.1 4.2 3.6 3.0 3.7 3.8 4.2 3.5 2.8
62 75 62 55 60 55 65 69 70
1.7 1.1 1.0 1.0 1.5 1.3 1.5 0.7 0.7
158 101 160 176 140 204 118 133 106
11.3 15.6 14.3 15.6 11.0 12.7 13.3 13.3 12.5
5.13 4.92 5.50 4.82 5.98 4.99 4.90 4.09 5.22
0 0 0 0 0 0 0 0
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0
Abbreviations: PA, prothombin activity (normal value: ->80%); GFR, glomerular filtration rate (measured as creatinine clearance); Hb, hemoglobin; GEC, galactose elimination capacity (normal value: >6 mg/kg/min); HE, hepatic encephalopathy.
d r i n k i n g for at l e a s t 1 y e a r before enrollment. Exclusion criter i a were cardiac, renal, r e s p i r a t o r y , neurologic or metabolic diseases, r e c e n t (within 4 months) g a s t r o i n t e s t i n a l hemorrhage, a n d history of previous ascites or diuretic t r e a t m e n t . The absence of ascites was confirmed by u l t r a s o n o g r a p h y . P o r t a l h y p e r t e n s i o n was a s c e r t a i n e d by the finding of a n enl a r g e d portal vein a t u l t r a s o n o g r a p h y or esophageal varices at endoscopy. Table I reports t h e m a i n clinical a n d l a b o r a t o r y f e a t u r e s of t h e patients. Only one was on drugs influencing the p a r a m e t e r s u n d e r study. I n this patient, t r e a t e d w i t h propranolol to p r e v e n t variceal rebleeding, the d r u g was stopped 10 days before entry. Nine h e a l t h y male volunteers, comparable for age (26 to 65 years, m e a n 54.2 _+ 2.6 years, P = .23), were enrolled as a control group. All the subjects ate a diet providing 150 m m o l / d a y of sodium for 5 days before a n d d u r i n g the study. They were a d m i t t e d to t h e hospital at 9 PM of the fifth day, a n d r e m a i n e d in bed from 10 PM to 7 AM in a single, quiet, d a r k e n e d room. Thereafter, t h e y were i n s t r u c t e d to leave the hospital, c a r r y on t h e i r n o r m a l activities (office or l a b o r a t o r y work), a n d r e t u r n to t h e h o s p i t a l for blood sampling. Meals were t a k e n a t 8 AM, 1 PM, and 8 PM. Blood s a m p l e s were collected at 11 PM a n d 7 AM (in supine subjects), 9 AM a n d 6 PM (in mobile subjects) t h r o u g h a heparinized catheter; before t h e l a s t two s a m p l i n g s were t a k e n , the subjects h a d been s e a t e d for 30 minutes. Blood was collected to d e t e r m i n e creatinine, sodium, ANP, a n d aldosterone concentrations, p l a s m a r e n i n activity a n d h e m a t o c r i t (Hct). To m e a s u r e r e n a l sodium excretion (UNaV), 24-hour u r i n e collections were performed s t a r t i n g from 10 PM both the day before a n d t h e d a y of the study. On the d a y of the experiment, c r e a t i n i n e excretion was also m e a s u r e d . Informed consent was o b t a i n e d from each p a r t i c i p a n t , a n d the s t u d y protocol was designed according to the principles of the Declaration of H e l s i n k i and approved by the Senior Staff C o m m i t t e e of our d e p a r t m e n t . Assays. Blood s a m p l i n g and a s s a y m e t h o d s for ANP, PRA, a n d aldosterone have been r e p o r t e d in detail elsewhere. 13'2°'2~ All s a m p l e s were a s s a y e d in a single run. Hct was d e t e r m i n e d by Technicon H2 (Technicon I n s t r u m e n t s Corporation, Tarrytown, NY). U r i n a r y a n d p l a s m a sodium concentrations were d e t e r m i n e d by selective ion electrodes and creatinine by a l k a l i n e picrate m e t h o d (Olympus A U 5000, Olympus Ltd, Tokyo, J a p a n ) . F i l t e r e d load of sodium was calculated as: FN~ = N a × GFR, where N a is the average value of the p l a s m a sodium concentrations m e a s u r e d t h r o u g h o u t t h e d a y a n d G F R is the g l o m e r u ] a r filtration r a t e (clearance of creatinine). Statistical Analysis. Results were expressed as m e a n _+ SEM. The v a r i a b l e d i s t r i b u t i o n was a s s e s s e d by Kolmo-
gorov-Smirnov n o r m a l i t y test, a n d logarithmic t r a n s f o r m a tion of the non-normally d i s t r i b u t e d p a r a m e t e r s was made. S t a t i s t i c a l significance of the changes observed within a n d between groups was e v a l u a t e d by m e a n s ofANOVA. Comparisons b e t w e e n r e p e a t e d m e a s u r e s were m a d e by m e a n s of ANOVA for r e p e a t e d m e a s u r e s . Correlation coefficients were derived by l i n e a r regression analysis. RESULTS
Plasma ANP significantly changed throughout the d a y i n b o t h c o n t r o l s u b j e c t s ( P = .001) a n d p a t i e n t s ( P < .001). T h e d a i l y p r o f i l e p a r a l l e l e d i n t h e t w o g r o u p s : A N P p e a k e d a t t h e e n d o f t h e s u p i n e p e r i o d (7 AM) a n d declined with the assumption of the upright posture. T h u s b o t h t h e 9 AM a n d 6 PM v a l u e s w e r e l o w e r t h a n those seen in the recumbence period and the mean d a i l y l e v e l (Fig. 1). D u r i n g t h e u p r i g h t p o s i t i o n , A N P declined only in the control group. At every sampling time, ANP of patients was signifi-
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CLOCK TIME ( h ) FIG. 1. Time course of plasma atrial natriuretic peptide concentration (ANP) during the 24 hours of the experiment. The arrow indicates the change of posture. The reported P value refers to the comparison between healthy and cirrhotic subjects (ANOVA for repeated measures), op <_ .033 with respect to the mean daily level, *P -< .049 vs. the supine values, §P = .002 vs. the 7:00 value, #P = .017 vs. the 9:00 value. - - • - - , controls; - - [] - - , patients with cirrhosis.
134
TREVISANI ET AL
HEPATOLOGY July 1995
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CLOCK TIME ( h ) FIG. 2. Time course of plasma renin activity (PRA) and hematocrit (HCT) during the 24 hours of the experiment. The arrow indicates the change of posture. The reported P value refers to the comparison between healthy and cirrhotic subjects (ANOVA for repeated measures), o p < .021 vs. mean daily level, *P -< .047 vs. the supine values, #P -< .014 vs. the 9:00 value, " P = .003 vs, the 23:00 value. - - • - - , controls; - - [] - - , patients with cirrhosis.
cantly elevated as compared with h e a l t h y controls (P = .01 or lower), so t h a t the mean daily level was significantly higher in the former (33.3 _+ 3.8 vs. 15.5 _+ 3.2 pg/mL, P = .004). Daily PRA changes were statistically significant (control subjects: P < .001; patients: P = .002) and ran in parallel in the two groups (Fig. 2). The PRA behavior was reciprocal to t h a t of ANP: it peaked at 9 AM and reached the lowest value at the end of the supine period. In both groups, the PRA levels seen in the upright position were significantly higher t h a n those found during recumbence. Throughout the study, PRA was significantly lower in patients t h a n in healthy volunteers (P = .019 or lower). Consequently, the PRA mean daily level was significantly lower in patients (0.76 +_ 0.23 vs. 1.66 _+ 0.21 ng/mL/h, P = .003). During the 24 hours of the experiment Hct fluctuated significantly in both the control (P = .001) and the
patient (P < .001) groups (Fig. 2). The daily profile paralleled t h a t of PRA: peak values were observed at 9 AM, and this value was significantly higher t h a n the supine values in both groups. Over the standing period, Hct declined in both healthy and cirrhotic subjects, so t h a t the value at 6 PM was significantly lower t h a n at 9 AM. At any given time, Hct was lower in patients t h a n in healthy controls (P = .003 or lower). Plasma aldosterone changes during the day were statistically significant in both groups (control subjects: P < .001; patients: P < .001). The zenith value occurred in the morning. With the exception of the 11 PM value, which was higher in patients (89 + 10 vs. 55 __ 5 pg/ mL, P -- .004), the time-related values did not differ in the two groups (7 AM: 158 _+ 18 vs. 155 _+ 22 pg/mL, P = .85; 9 AM: 166 _+ 16 vs. 155 _+ 14 pg/mL, P = .63; 6 PM: 96 _+ 11 vs. 88 _ 10 pg/mL, P = .62). The mean daily level was similar in cirrhotic and healthy subjects (122 _+ 11 vs. 119 _+ 9 pg/mL, P = .82). The ratios between mean daily levels of ANP and aldosterone (ANP/aldosterone: 0.29 _+ 0.05 vs. 0.14 _+ 0.03, P = .012) and between mean daily levels of ANP and PRA (ANP/PRA: 67 _+ 14 vs. 12 _+ 3, P < .001) were higher in the cirrhotic group. FNa did not differ between healthy subjects and cirrhotic patients (17.1 _+ 1.4 vs. 20.4 _+ 1.7 mmol/min, P = .69). The day before and during the experiment, daily UNaV was well adapted to the intake and did not change either in control subjects (day 1:152 _+ 11 mmol; day 2:138 _+ 12.5 mmol, P = .14) or in patients (day 1:143 _+ 15 mmol; day 2:148 _+ 29 mmol, P = .49) (Fig. 3). No statistically significant differences were found between the two groups (day 1: P = .55, day 2: P = .53). Finally, body weight remained steady in both groups (Fig. 3). Mean arterial pressure of controls and cirrhotic did not differ at any given time (11 PM: 95 _+ 4 vs. 94 _+ 3 m m H g , P = . 7 6 ; 7 A M : 9 0 + 6 v s . 98_+ 3 m m H g , P
80
200 o
E 60
E 150
~, I--r"
~ 100
40-~w
z ~
20 m
f21 0
50
o 0 DAY 1
DAY 2
FIG. 3. Body weight (lines) and daily renal excretion of sodium (bars). Note t h a t the daily sodium intake was 150 mmol. Dashed bars: healthy subjects, solid bars: cirrhotic patients. Day 1: day before the experiment, day 2: day of the experiment. - - • - - , controls; - - [] - - , patients with cirrhosis.
HEPATOLOGYVol. 22, No. 1, 1995
TREVISANI ET AL 135
the depressed PRA levels seen in our patients, along with the results of many other studies employing different protocols and techniques and analyzing compensated patients selectively, 13'15'3~ are consistent with a condition of central volume expansion. The resetting at persistently elevated ANP plasma levels did not affect the intrinsic surge toward the zenith but was able to abrogate the fall to the nadir. This finding is in line with the weakened rhythmicity of ANP secretion documented in compensated patients maintained supine 37 and could be again an effect of an increased central volemia. The daily renal excretion of sodium of our cirrhotic patients was well balanced to the intake and similar to that of healthy individuals. This finding attests that, even if the patients had previously developed a renal fluid retention responsible for the increased blood volDISCUSSION ume, they reached a new steady state. It is also worth In supine compensated cirrhotic patients, spot mea- noting that the expansion of total and central blood surements of plasma ANP have provided conflicting volume and the elevation of ANP cannot be prevented results. 912'152° Two studies dealing with sitting or by low-sodium diet (20 mmol/day). 36 From the precedstanding patients have found normal or insignificantly ing it can be inferred that, at various salt intakes, inincreased ANP levels. ~'14 This heterogeneous picture creased ANP levels are an adaptive mechanism needed may be attributable to differences in the patient selec- to maintain the sodium balance. As in experimental tion and experimental protocol among the studies. 26 cirrhosis, 3s in preascitic h u m a n cirrhosis some mechaThe current study first evaluated plasma ANP concen- nisms favoring salt retention would hinder a full-blown tration at different clock times in preascitic cirrhotic renal response to the peptide. The results of ANP infupatients on normal sodium diet and carrying on their sion or stimulation of its secretion provide further eviusual activities. It clearly demonstrated that, in this dence of this. The bolus administration of synthetic acondition, patients maintained higher ANP levels than human-ANP induced a lower natriuretic response in healthy subjects, regardless of time of day and posture. patients without or with minimal ascites than in norDespite a resetting of plasma ANP at a higher level, mal subjects. 19'21 However, the abnormal blood presthe daily profile of the peptide values was near normal. sure fall experienced by patients in these experiments Because atrial distension is the main stimulus for ANP likely contributed to their blunted natriuretic response. release, 1 variations of posture, which prompt blood vol- More intriguing, 1-hour head-out water immersion ume redistribution between the central and peripheral evoked a reduced natrinresis despite a normal ANP area, 13 would be expected to be crucial in setting circu- increase, ~4 and normal supine-induced natriuresis was lating ANP levels. Consistently, the postural change achieved thanks to an exaggerated ANP secretion. 39 likely accounted for the prominent variations of plasma Finally, the hypernatriuresis induced by 3 hours' water ANP seen in both healthy controls and patients. In fact, immersion was coupled with an elevation of plasma the decline of ANP concentration closely coincided with ANP far greater in patients than in healthy controls the assumption of the upright position and the eleva- and disproportionate to the magnitude of the achieved tion of PRA (a marker of effective volemia 2~) and Hct, natriuresis. 22 which reflects the gravity-induced extravascular shift Because the presence of either abnormal precursors of protein-free fluid in the dependent body regionsY In or structurally defective ANP has been ruled out in addition to the volume-induced changes, the intrinsic cirrhosis, 4° a renal hyporesponsiveness to the peptide rhythmicity of ANP secretion 2s'29 probably contributed could be inferred. Contrary to what happens in sodiumin setting its plasma levels in both groups. In fact, ANP retaining patients, 5'~'s'1~ the elevation of ANP in preof patients peaked in the morning as in the control ascitic cirrhosis cannot be attributed to the need of counteracting increased levels of angiotensin II or aldogroup. The mechanism(s) responsible for the ANP increase sterone. In fact, according to several previous reports, 4~ in cirrhosis have not been definitively settled. Although PRA of our patients was reduced and plasma aldostea contribution by a reduced clearance cannot be ex- rone only transiently increased, so that its mean daily cluded, ~° it is likely that the ANP augmentation is level was equal in the two groups. The coexistence of mainly due to hypersecretion. 3~'~2The increased release normal plasma aldosterone along with depressed PRA from atria would be eventually caused by the expansion could be attributed to either increased adrenal sensitivof total and central plasma v o l u m e . 3'15'17'3~'34 Such an ity to angiotensin I142 or impaired hepatic metabolism assumption is not supported by the findings by Henrik- of the hormone. 41'48 sen et al, 3~ who found reduced central blood volume in Sympathetic nervous system hypertone has been cirrhosis with first-pass clearance technique. However, claimed to contribute to renal sodium retention in cir-
= .29; 9 AM: 87 _+ 4 vs. 95 +_ 3 mm Hg, P -- .14; 6 PM: 90 +_ 3 vs. 93 _+ 3 pg/mL, P = .53). As a result, the mean daily levels were similar (91 ± 4 vs. 95 _+ 3, P = .40). Time-related and mean daily values of heart rate were also similar in the two groups (11 PM: 72 ± 3 vs. 7 4 ± 3 b p m , P = .71; 7 AM: 69 +__2 vs. 68 ± 2 b p m , P = .76; 9 AM: 71 ± 3 vs. 71 ± 2 bpm, P = .78; 6 PM: 71 ± 3 vs. 71 ± 2 bpm, P = .97; mean daily value: 71 ± 2 vs. 71 ± 2, P = .96). The correlations between UN~V and ANP, aldosterone, ANP/aldosterone, and ANP/PRA were assessed. Weak relationships were found between UNaV and mean daily plasma levels o f A N P (r = .64, P = .058) in healthy subjects, and between UNaV and log ANP/PRA (r = .66, P = .052) in patients.
136
TREVISANI ET AL
rhosis, t5 However, in agreement with many antecedent studies, 1°'~7'2°'4°'46 plasma norepinephrine concentrat i o n - i n d e x of sympathetic activity--of our patients was not elevated (unpublished observations). Our data also excluded that ANP hypoeffectiveness was caused by a manifest impaired renal perfusion, because the hemodynamic pattern (mean arterial pressure and heart rate), glomerular filtration rate, and filtered load of sodium did not differ between patients and controls. However, the relationship between ANP/ PRA and sodium excretion observed in the patient group could reflect the critical dependence of renal sodium handling from effective volemia in cirrhosis. The actual reasons for the blunted natriuretic response to ANP in preascitic cirrhosis cannot be deduced from the current study. However, it could be hypothesized that this defect results from the cooperation of several subtle abnormalities such as (1) tubular hypersensitivity to aldosterone33'46; (2) increased density of C(clearance)-receptors of ANP in the kidney (so far described only in cirrhotic rats with ascites4), or defective second messenger production. In this respect, it is worth noting that the ANP-induced cyclic guanosine monophosphate generation by isolated glomeruli is slightly reduced in preascitic experimental cirrhosis, 32 and an insufficient cGMP generation despite normal increase of plasma ANP has been claimed to be responsible for the inability to escape from the salt-retaining effect of fludrocortisone by compensated patientsY However, the results of Skorecki et al 5 did not confirm the defective cGMP generation even in sodium-retaining cirrhosis; (3) slight increase in proximal tubular reabsorption of sodium, 4s which diminishes sodium delivery to the collecting duct, site of ANP action. In conclusion, the current study clearly showed that preascitic cirrhotic patients on normal sodium diet and engaged in their usual activities have steadily increased plasma ANP. Despite this, renal sodium excretion was not greater than in normal subjects, and it was well adapted to the intake. The blunted natriuretic action of ANP cannot be attributed to the activation of the renin-angiotensin-aldosterone and sympathoadrenergic systems. However, the presence of other mechanism(s) promoting a subtle trend to renal sodium retention and opposing the ANP effects cannot be excluded. This defect could be involved in the pathogenesis of the deranged renal sodium handling that in preascitic patients becomes manifest only under sodium load 49'5° and mineralocorticoid administration. 47'51 REFERENCES 1. Goetz KL. Physiology and pathophysiology of atrial peptides. Am J Physiol 1988;254:El-El5. 2. Warner L, Skorecki K, Blendis LM, Epstein M. Atrial natriuretic factor and liver disease. HEPATOLOGY1993; 17:500-513. 3. Wong F, Blendis LM. Pathophysiology of sodium retention and ascites formation in cirrhosis: role of atrial natriuretic factor. Semin Liver Dis 1994; 14:59-70. 4. Gerbes AL, Kollenda MC, VoUmar AM, Reichen J, Vakil N, Scarborough RM. Altered density of glomerular binding sites for atrial natriuretic factor in bile duct-ligated rats with ascites. HEPATOLOGY 1991; 13:562-566.
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