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Lack of Effect of Prostaglandin Inhibition on Calcium Excretion in Normal Volunteers
0022-534 7/85/1336-1093$02.00/0 Vol. 133, June
THE JOURNAL OF UROLOGY
Copyright © 1985 by The Williams & Wilkins Co.
Printed in U.S.A.
LACK OF EFFECT OF PROSTAGLANDIN INHIBITION ON CALCIUM EXCRETION IN NORMAL VOLUNTEERS VITO K. ROCCO, KHASHAYAR SAKHAEE, CHARLES Y. C. PAK, AND D_ CRAIG BRATER* From the Departments of Pharmacology and Internal Medicine, University of Texas Health Science Center at Dallas, Southwestern Medical School, Dallas, Texas
ABSTRACT
Recent data have shown that administration of indomethacin to patients wth hypercalciuric nephrolithiasis decreased urinary calcium excretion, implying a possible pathogenic role for renal prostaglandins in hypercalciuria. To explore this hypothesis we administered indomethacin, ketoprofen and aspirin to normal volunteers for 6 days and assessed daily creatinine clearance and urinary excretion of sodium and calcium. In contrast to previous studies, subjects were maintained on a constant metabolic diet. These nonsteroidal anti-inflammatory drugs decreased urinary sodium excretion but had no effect on creatinine clearance or urinary calcium excretion. In summary, our data do not support an important physiologic role of renal prostaglandins in renal calcium excretion in normal subjects. The association of hypercalciuria with calcium nephrolithiasis has long been recognized. It has previously been suggested that hypercalciuria in the setting of normocalcemia occurs as 2 major variants, absorptive and renal hypercalciuria, depending on whether the primary derangement is an enhanced intestinal absorption or an impaired renal tubular reabsorption of calcium.1·2 Among the pathophysiologic mechanisms previously described,2-5 Buck et al. 6 • 7 have recently suggested that renal prostaglandins, presumably prostaglandin E2 (PGE2), might play an important etiologic role in the renal handling of calcium in patients with hypercalciuric nephrolithiasis. In order to further investigate this hypothesis, we studied 6 normal subjects who received nonsteroidal anti-inflammatory drugs (NSAID) under balance conditions, assessing creatinine clearance and urinary excretion of sodium and calcium. Our data do not support an effect of these drugs on renal calcium excretion in this setting. MATERIALS AND METHODS
Six normal men, 23 to 35 years old, volunteered for this study. They had no prior history of nephrolithiasis, chronic renal insufficiency or liver disease and no prior treatment with vitamin D or any known vitamin D antagonist such as glucocorticoids or phenytoin. Patients were all ambulatory and in good health. Dietary histories were obtained in all subjects and intake of calcium and vitamin D was normal in all cases. Serum values for calcium, phosphorous (P), alkaline phosphatase and immunoreactive parathyroid hormone (PTH) were normal. All subjects were evaluated at the General Clinical Research Center after obtaining signed informed consent. Patients ingested a constant metabolic diet containing 400 mg. calcium, 800 mg. P, 150 mEq sodium, 60 to 80 mEq potassium, and 3 liters of fluid intake on each of the 9 days of study. Twentyfour-hour urine samples were collected each day and analyzed for sodium, calcium and creatinine. Serum electrolytes, calcium and creatinine were also measured daily. Most subjects were studied on 3 different occasions while taking 1 of 3 NSAIDs. After a 4 day equilibration period, indomethacin 50 mg. 3 times Accepted for publication February 15, 1985. * Requests for reprints: Dept. of Pharmacology, University of Texas Health Science Center, Southwestern Medical School, 5323 Harry Hines Blvd., Dallas, TX 75235. Supported by USPHS grants MOl-RR-00633, POl-AM-20543 and lR01-AM27059 and Research Career Development Award l-K04AM00705.
a day (no. = 6), ketoprofen 50 mg. 4 times a day (no. = 5), or aspirin 325 mg. 4 times a day (no. = 4) were administered on days 5 through 9 of the study. Each study period was separated by at least 2 weeks and the different phases were conducted in random order. Urinary calcium was determined by atomic absorption spectrophotometry and urinary sodium by an ion selective electrode. All results were expressed as the mean ± standard deviation. Statistical significance was determined by means of the paired t test. RESULTS
Twenty-four-hour urinary calcium excretion and values for creatinine clearance were not significantly decreased by any of the 3 NSAIDs at any point in the study (fig. 1). Rather, calcium excretion was actually increased slightly on the first day (day 5) of aspirin therapy and on the third day (day 7) of indomethacin therapy. The increase on the first day of indomethacin therapy was not significant. Sodium excretion exhibited a much different response (fig. 1). Significant decreases in twenty-fourhour urinary sodium excretion occurred on the first and fourth days (days 5 and 8) of ketoprofen therapy and on all 5 days of aspirin therapy; indomethacin did not cause a significant decrease in urinary sodium excretion. There was no consistent effect of the NSAIDs on creatinine clearance (table 1). DISCUSSION
Buck and colleagues6 • 7 have recently reported an association between inhibition of renal prostaglandins and urinary calcium excretion in hypercalciuric renal stone forming patients. The present study was undertaken to determine if prostaglandins play a physiologic role in the renal handling of calcium. Six normal male subjects were studied under balance conditions of dietary calcium and sodium intake. The effects of 2 different NSAIDs and of aspirin were examined. In general, sodium excretion decreased but no effect was observed on calcium excretion or creatinine clearance despite our using a 2-fold greater dose of indomethacin than did Buck. 7 Several factors may account for the different findings in our study compared to those of Buck et al. 6 • 7 First, our patients were studied in a General Clinical Research Center with strict control of dietary sodium, calcium and fluid intake; medications other than NSAIDs were not taken by any of our patients. On the other hand, diet and fluids were uncontrolled in prior studies. 6 • 7 However, we feel that random variation in diet or 1093
1094
ROCCO AND ASSOCIATES TABLE
1. Lack of effect of indomethacin, aspirin and ketoprofen on creatinine clearance (mean± SD) Treatment Day
Control (Days 1-4)
5
118 ± 15 118 ± 14 124 ± 10
lndomethacin Aspirin Ketoprofen
120 117 130
6 18 25
INDOMETHACIN
300
300
250 200 150
250 200 150
100
100
50
50
I
l:: ASPIRIN
300
300
250
Urine Sodium 200 (UNal 150 mEq/day
Urine Calcium (Ucal
200
mg/day
150
250
100 50
100 50
t
I KETOPROFEN
300 250
300 250
Uca
r)J_r_r_J_I
200 150 100
200 150 100
!,!_..1-r·,1~1
50
1
I (1-4)
** I 5
I 6
** I 7
I 8
50
u
ra
9
I 10
Control Period
Day of Therapy
FIG. 1. Effects of indomethacin (top panel), aspirin (middle panel) and ketoprofen (bottom panel) on 24 hr. urinary excretion of calcium (Uca, left ordinate) and sodium (UNa, right ordinate). * p <0.05; ** p <0.025; + p <0.0025.
volume status are unlikely explanations of the anticalciuric effect, since the effect of NSAID administration on urinary calcium excretion was so consistent and of such magnitude in their patients. Second, the subjects in our study were all normal volunteers with none of the known stimuli for renal prostaglandin production. 8- 11 The physiology of renal calcium handling and its relationship to prostaglandins in normal subjects might differ from that of patients with nephrolithiasis. For example, the patients studied by Buck et al. 6 • 7 had elevated basal values for endogenous creatinine clearance and hypercalciuria. These disturbances could conceivably reflect enhanced renal PGE 2 activity or PGE2 excess. If the data by Buck et al. 6 • 7 are indeed reproducible under balance study conditions, a new role of prostaglandins in the pathogenesis of hypercalciuric nephrolithiasis may be postulated. It is well known that calcium and sodium handling by the kidney parallel one another in the proximal portions of the nephron,1 2 whereas at the level of the distal convoluted tubule the handling of these cations may be dissociated. 1 'i Stokes has demonstrated in vitro that prostaglandins inhibit chloride reab-
6
7
8
9
138 ± 16 115 ± 14 118 ± 16
134 ± 11 118 ± 19 126 ± 10
128 ± 20 126 ± 16 120 ± 12
120 ± 11 127 ± 11 114 ± 19
sorption in the medullary segment of the thick ascending limb of the loop of Henle. 14 Kaojarern et al. have recently published clearance data in humans supporting a similar effect in vivo. 15 Since sodium, chloride and calcium all move in parallel fashion at this nephron site, it seems reasonable to conclude that NSAIDs should decrease calcium excretion when they are administered to patients in whom renal prostaglandin synthesis is activated. The present study has demonstrated that such an effect is not observed in normal, sodium replete patients. The work of Buck and his colleagues,6· 7 therefore, suggests that hypercalciuric nephrolithiasis may entail activation of renal prostaglandin synthesis by an unknown mechanism. Further detailed studies are needed in such patients confirming these findings and probing possible mechanisms. REFERENCES
1. Pak, C. Y. C., Ohata, M., Lawrence, E. C. and Snyder, W.: The hypercalciurias: causes, parathyroid functions and diagnostic criteria. J. Clin. Invest., 54: 387, 1974. 2. Pak, C. Y. C.: Physiological basis for absorptive and renal hypercalciurias. Am. J. Physiol., 237: F415, 1979. 3. Sakhaee, K., Brater, D. C. and Pak, C. Y. C.: An exaggerated natriuretic response to hydrochlorothiazide (TZ) in renal hypercalciuria (RH) but not in absorptive hypercalciuria (AH). Clin Res., 31: 396, 1983 (Abstract). 4. Gray, R. W., Wilz, D. R., Caldas, A. E. and Lemann, J.: The importance of phosphate in regulating plasma 1, 25-(0Hh-vitamin D levels in humans: studies in healthy subjects, in calciumstone formers and in patients with primary hyperparathyroidism. J. Clin. Endocrinol. Metab., 45: 299, 1977. 5. Coe, F. L. and Kavalach, A.G.: Hypercalciuria and hyperuricosuria in patients with calcium nephrolithiasis. N. Engl. J. Med., 291: 1344, 1974. 6. Buck, A. C., Lote, C. J. and Blacklock, N. J.: The influence of renal prostaglandins on glomerular filtration rate (GFR) and calcium excretion in urolithiasis. Br. J. Urol., 53: 485, 1981. 7. Buck, A. C., Lote, C. J. and Sampson, W. F.: The influence of renal prostaglandins on urinary calcium excretion in idiopathic urolithiasis. J. Urol., 129: 421, 1983. 8. Clive, D. M. and Stoff, J. S.: Renal syndromes associated with nonsteroidal anti-inflammatory drugs. N. Engl. J. Med., 310: 563, 1984. 9. Garella, S. and Matarese, R. A.: Renal effects of prostaglandins and clinical adverse effects of nonsteroidal anti-inflammatory agents. Medicine, 63: 165, 1984. 10. Weber, P. C., Scherer, B., Siess, W., Held, E. and Schuermann, J.: Formation and action of prostaglandins in the kidney. Klin. Wochenschr., 57: 1021, 1979. 11. Levy, M., Wexler, M. J. and Fechner, C.: Renal perfusion in dogs with experimental hepatic cirrhosis: role of prostaglandins. Am. J. Physiol., 245: F521, 1983. 12. Edwards, B. R., Baer, P. C., Sutton, R. A. L. and Dirks, J. H.: Micropuncture study of diuretic effects on sodium and calcium reabsorption in the dog nephron. J. Clin. Invest., 52: 2418, 1973. 13. Costanzo, L. S. and Windhager, E. E.: Calcium and sodium transport by the distal convoluted tubule of the rat. Am. J. Physiol., 235: F492, 1978. 14. Stokes, J. B.: Effect of prostaglandin E 2 on chloride transport across the rabbit thick ascending limb of Henle. Selective inhibition of the medullary portion. J. Clin. Invest., 64: 495, 1979. 15. Kaojarern, S., Chennavasin, P., Anderson, S. and Brater, D. C.: Nephron site of effect of nonsteroidal anti-inflammatory drugs on solute excretion in humans. Am. J. Physiol., 244: F134, 1983.
THE JOURNAL OF UROLOGY
Copyright © 1985 by The Williams & Wilkins Co.
Printed in U.S.A.
LACK OF EFFECT OF PROSTAGLANDIN INHIBITION ON CALCIUM EXCRETION IN NORMAL VOLUNTEERS VITO K. ROCCO, KHASHAYAR SAKHAEE, CHARLES Y. C. PAK, AND D_ CRAIG BRATER* From the Departments of Pharmacology and Internal Medicine, University of Texas Health Science Center at Dallas, Southwestern Medical School, Dallas, Texas
ABSTRACT
Recent data have shown that administration of indomethacin to patients wth hypercalciuric nephrolithiasis decreased urinary calcium excretion, implying a possible pathogenic role for renal prostaglandins in hypercalciuria. To explore this hypothesis we administered indomethacin, ketoprofen and aspirin to normal volunteers for 6 days and assessed daily creatinine clearance and urinary excretion of sodium and calcium. In contrast to previous studies, subjects were maintained on a constant metabolic diet. These nonsteroidal anti-inflammatory drugs decreased urinary sodium excretion but had no effect on creatinine clearance or urinary calcium excretion. In summary, our data do not support an important physiologic role of renal prostaglandins in renal calcium excretion in normal subjects. The association of hypercalciuria with calcium nephrolithiasis has long been recognized. It has previously been suggested that hypercalciuria in the setting of normocalcemia occurs as 2 major variants, absorptive and renal hypercalciuria, depending on whether the primary derangement is an enhanced intestinal absorption or an impaired renal tubular reabsorption of calcium.1·2 Among the pathophysiologic mechanisms previously described,2-5 Buck et al. 6 • 7 have recently suggested that renal prostaglandins, presumably prostaglandin E2 (PGE2), might play an important etiologic role in the renal handling of calcium in patients with hypercalciuric nephrolithiasis. In order to further investigate this hypothesis, we studied 6 normal subjects who received nonsteroidal anti-inflammatory drugs (NSAID) under balance conditions, assessing creatinine clearance and urinary excretion of sodium and calcium. Our data do not support an effect of these drugs on renal calcium excretion in this setting. MATERIALS AND METHODS
Six normal men, 23 to 35 years old, volunteered for this study. They had no prior history of nephrolithiasis, chronic renal insufficiency or liver disease and no prior treatment with vitamin D or any known vitamin D antagonist such as glucocorticoids or phenytoin. Patients were all ambulatory and in good health. Dietary histories were obtained in all subjects and intake of calcium and vitamin D was normal in all cases. Serum values for calcium, phosphorous (P), alkaline phosphatase and immunoreactive parathyroid hormone (PTH) were normal. All subjects were evaluated at the General Clinical Research Center after obtaining signed informed consent. Patients ingested a constant metabolic diet containing 400 mg. calcium, 800 mg. P, 150 mEq sodium, 60 to 80 mEq potassium, and 3 liters of fluid intake on each of the 9 days of study. Twentyfour-hour urine samples were collected each day and analyzed for sodium, calcium and creatinine. Serum electrolytes, calcium and creatinine were also measured daily. Most subjects were studied on 3 different occasions while taking 1 of 3 NSAIDs. After a 4 day equilibration period, indomethacin 50 mg. 3 times Accepted for publication February 15, 1985. * Requests for reprints: Dept. of Pharmacology, University of Texas Health Science Center, Southwestern Medical School, 5323 Harry Hines Blvd., Dallas, TX 75235. Supported by USPHS grants MOl-RR-00633, POl-AM-20543 and lR01-AM27059 and Research Career Development Award l-K04AM00705.
a day (no. = 6), ketoprofen 50 mg. 4 times a day (no. = 5), or aspirin 325 mg. 4 times a day (no. = 4) were administered on days 5 through 9 of the study. Each study period was separated by at least 2 weeks and the different phases were conducted in random order. Urinary calcium was determined by atomic absorption spectrophotometry and urinary sodium by an ion selective electrode. All results were expressed as the mean ± standard deviation. Statistical significance was determined by means of the paired t test. RESULTS
Twenty-four-hour urinary calcium excretion and values for creatinine clearance were not significantly decreased by any of the 3 NSAIDs at any point in the study (fig. 1). Rather, calcium excretion was actually increased slightly on the first day (day 5) of aspirin therapy and on the third day (day 7) of indomethacin therapy. The increase on the first day of indomethacin therapy was not significant. Sodium excretion exhibited a much different response (fig. 1). Significant decreases in twenty-fourhour urinary sodium excretion occurred on the first and fourth days (days 5 and 8) of ketoprofen therapy and on all 5 days of aspirin therapy; indomethacin did not cause a significant decrease in urinary sodium excretion. There was no consistent effect of the NSAIDs on creatinine clearance (table 1). DISCUSSION
Buck and colleagues6 • 7 have recently reported an association between inhibition of renal prostaglandins and urinary calcium excretion in hypercalciuric renal stone forming patients. The present study was undertaken to determine if prostaglandins play a physiologic role in the renal handling of calcium. Six normal male subjects were studied under balance conditions of dietary calcium and sodium intake. The effects of 2 different NSAIDs and of aspirin were examined. In general, sodium excretion decreased but no effect was observed on calcium excretion or creatinine clearance despite our using a 2-fold greater dose of indomethacin than did Buck. 7 Several factors may account for the different findings in our study compared to those of Buck et al. 6 • 7 First, our patients were studied in a General Clinical Research Center with strict control of dietary sodium, calcium and fluid intake; medications other than NSAIDs were not taken by any of our patients. On the other hand, diet and fluids were uncontrolled in prior studies. 6 • 7 However, we feel that random variation in diet or 1093
1094
ROCCO AND ASSOCIATES TABLE
1. Lack of effect of indomethacin, aspirin and ketoprofen on creatinine clearance (mean± SD) Treatment Day
Control (Days 1-4)
5
118 ± 15 118 ± 14 124 ± 10
lndomethacin Aspirin Ketoprofen
120 117 130
6 18 25
INDOMETHACIN
300
300
250 200 150
250 200 150
100
100
50
50
I
l:: ASPIRIN
300
300
250
Urine Sodium 200 (UNal 150 mEq/day
Urine Calcium (Ucal
200
mg/day
150
250
100 50
100 50
t
I KETOPROFEN
300 250
300 250
Uca
r)J_r_r_J_I
200 150 100
200 150 100
!,!_..1-r·,1~1
50
1
I (1-4)
** I 5
I 6
** I 7
I 8
50
u
ra
9
I 10
Control Period
Day of Therapy
FIG. 1. Effects of indomethacin (top panel), aspirin (middle panel) and ketoprofen (bottom panel) on 24 hr. urinary excretion of calcium (Uca, left ordinate) and sodium (UNa, right ordinate). * p <0.05; ** p <0.025; + p <0.0025.
volume status are unlikely explanations of the anticalciuric effect, since the effect of NSAID administration on urinary calcium excretion was so consistent and of such magnitude in their patients. Second, the subjects in our study were all normal volunteers with none of the known stimuli for renal prostaglandin production. 8- 11 The physiology of renal calcium handling and its relationship to prostaglandins in normal subjects might differ from that of patients with nephrolithiasis. For example, the patients studied by Buck et al. 6 • 7 had elevated basal values for endogenous creatinine clearance and hypercalciuria. These disturbances could conceivably reflect enhanced renal PGE 2 activity or PGE2 excess. If the data by Buck et al. 6 • 7 are indeed reproducible under balance study conditions, a new role of prostaglandins in the pathogenesis of hypercalciuric nephrolithiasis may be postulated. It is well known that calcium and sodium handling by the kidney parallel one another in the proximal portions of the nephron,1 2 whereas at the level of the distal convoluted tubule the handling of these cations may be dissociated. 1 'i Stokes has demonstrated in vitro that prostaglandins inhibit chloride reab-
6
7
8
9
138 ± 16 115 ± 14 118 ± 16
134 ± 11 118 ± 19 126 ± 10
128 ± 20 126 ± 16 120 ± 12
120 ± 11 127 ± 11 114 ± 19
sorption in the medullary segment of the thick ascending limb of the loop of Henle. 14 Kaojarern et al. have recently published clearance data in humans supporting a similar effect in vivo. 15 Since sodium, chloride and calcium all move in parallel fashion at this nephron site, it seems reasonable to conclude that NSAIDs should decrease calcium excretion when they are administered to patients in whom renal prostaglandin synthesis is activated. The present study has demonstrated that such an effect is not observed in normal, sodium replete patients. The work of Buck and his colleagues,6· 7 therefore, suggests that hypercalciuric nephrolithiasis may entail activation of renal prostaglandin synthesis by an unknown mechanism. Further detailed studies are needed in such patients confirming these findings and probing possible mechanisms. REFERENCES
1. Pak, C. Y. C., Ohata, M., Lawrence, E. C. and Snyder, W.: The hypercalciurias: causes, parathyroid functions and diagnostic criteria. J. Clin. Invest., 54: 387, 1974. 2. Pak, C. Y. C.: Physiological basis for absorptive and renal hypercalciurias. Am. J. Physiol., 237: F415, 1979. 3. Sakhaee, K., Brater, D. C. and Pak, C. Y. C.: An exaggerated natriuretic response to hydrochlorothiazide (TZ) in renal hypercalciuria (RH) but not in absorptive hypercalciuria (AH). Clin Res., 31: 396, 1983 (Abstract). 4. Gray, R. W., Wilz, D. R., Caldas, A. E. and Lemann, J.: The importance of phosphate in regulating plasma 1, 25-(0Hh-vitamin D levels in humans: studies in healthy subjects, in calciumstone formers and in patients with primary hyperparathyroidism. J. Clin. Endocrinol. Metab., 45: 299, 1977. 5. Coe, F. L. and Kavalach, A.G.: Hypercalciuria and hyperuricosuria in patients with calcium nephrolithiasis. N. Engl. J. Med., 291: 1344, 1974. 6. Buck, A. C., Lote, C. J. and Blacklock, N. J.: The influence of renal prostaglandins on glomerular filtration rate (GFR) and calcium excretion in urolithiasis. Br. J. Urol., 53: 485, 1981. 7. Buck, A. C., Lote, C. J. and Sampson, W. F.: The influence of renal prostaglandins on urinary calcium excretion in idiopathic urolithiasis. J. Urol., 129: 421, 1983. 8. Clive, D. M. and Stoff, J. S.: Renal syndromes associated with nonsteroidal anti-inflammatory drugs. N. Engl. J. Med., 310: 563, 1984. 9. Garella, S. and Matarese, R. A.: Renal effects of prostaglandins and clinical adverse effects of nonsteroidal anti-inflammatory agents. Medicine, 63: 165, 1984. 10. Weber, P. C., Scherer, B., Siess, W., Held, E. and Schuermann, J.: Formation and action of prostaglandins in the kidney. Klin. Wochenschr., 57: 1021, 1979. 11. Levy, M., Wexler, M. J. and Fechner, C.: Renal perfusion in dogs with experimental hepatic cirrhosis: role of prostaglandins. Am. J. Physiol., 245: F521, 1983. 12. Edwards, B. R., Baer, P. C., Sutton, R. A. L. and Dirks, J. H.: Micropuncture study of diuretic effects on sodium and calcium reabsorption in the dog nephron. J. Clin. Invest., 52: 2418, 1973. 13. Costanzo, L. S. and Windhager, E. E.: Calcium and sodium transport by the distal convoluted tubule of the rat. Am. J. Physiol., 235: F492, 1978. 14. Stokes, J. B.: Effect of prostaglandin E 2 on chloride transport across the rabbit thick ascending limb of Henle. Selective inhibition of the medullary portion. J. Clin. Invest., 64: 495, 1979. 15. Kaojarern, S., Chennavasin, P., Anderson, S. and Brater, D. C.: Nephron site of effect of nonsteroidal anti-inflammatory drugs on solute excretion in humans. Am. J. Physiol., 244: F134, 1983.