Nitric oxide synthase inhibition mediated afferent and efferent arteriolar vasoconstriction involves L-type calcium channel activation

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POSTERS: Kidney and Hypertension

pressures (BP) compared to the EH patients (systolic BP 213 ⫾ 4 vs. 175 ⫾ 2 mm Hg, P ⬍ 0.0001; diastolic BP 111 ⫾ 2 vs. 98 ⫾ 1, P ⬍ 0.0001). Following Institutional Review Board approval, follow-up information was gathered by mail, telephone, and/or query of the Social Security Death Index through November 30, 2001. Comparisons were made using t-tests, chi-square, and log-rank tests. Cox proportional hazards regression was used in survival analyses to adjust for baseline differences between the groups. During an average of 12.5 years of possible follow-up, 28 of the 58 (48.3%) RVH patients died compared with 43 of 174 (24.7%) EH patients. The unadjusted risk ratio showed a 1.95-fold increase in all-cause mortality (95% confidence interval 1.35– 2.83, P ⬍ 0.01) in RVH patients compared to EH patients. After adjustment for baseline systolic blood pressure, RVH was associated with a 1.96-fold increase in mortality (95% confidence interval 1.06 –3.63, P ⬍ 0.01) compared to EH patients. These data suggest that, despite successful revascularization, RVH patients still have an increased mortality compared to EH patients. Key Words: Renal Artery Stenosis, Outcomes, Case Control

P-154 EVIDENCE THAT PHOSPHODIESTERASE 4B PLAYS A MECHANISTIC ROLE IN SALT-ADAPTATION AND IS A THERAPEUTIC TARGET FOR HYPERTENSION IN THE DAHL RAT Alan Jung, Marie K. Baraoidan, Kumar Kotlo, Robert S. Danziger. Cardiology, University of Illinois at Chicago, Chicago, IL. Cyclic nucleotide phosphodiesterases (PDE) regulate many cellular functions in the cardiovascular system such as contractility, motility and transcription. However, their role in blood pressure regulation is poorly understood. In the present study we investigated the effect of rolipram, an inhibitor of PDE4 activity, on salt-sensitive hypertension. Mean blood pressure (MBP) was measured by continuous recording radiotelemetry in hypertensive Dahl salt-sensitive (SS) rats (on 8% NaCl 10 days). Rolipram (10mg/kg/IP) reduced mean arterial BP (179⫹13 mm Hg to 81⫹11 mm Hg (n ⫽ 3; p⬍0.01)) for 3 days (fig below). In order to further probe a role of PDE4 in salt-adaptation and hypertension, the effect of dietary salt on PDE4B, the preeminent renal isoform of PDE4, was examined in Dahl SS and salt-resistant (SR) rats. Renal PDE4B protein abundance, determined by western blot, was the same in Dahl SR and SS rats treated with 0.3%, however, was 2.5 fold less (P⬍0.05) in SR versus SS rats on 8% NaCl. Overall the results suggest that PDE4B abundance plays a mechanistic role in adaptation to a high salt diet. Furthermore, this implicates beta-adrenergic signaling in salt-adaptation since PDE4B is a cAMP specific PDE.

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P-155 RELATIONSHIPS BETWEEN CIRCULATING PLASMA LEVELS OF INFLAMMATORY MARKERS AND URINARY ALBUMIN EXCRETION RATE IN UNTREATED SUBJECTS WITH ESSENTIAL HYPERTENSION K. Dimitriadis, C. Tsioufis, M. Toutouza, C. Stefanadis, I. Kallikazaros. Cardiology Department, Hippokration Hospital, Athens, Greece. Inflammatory processes are closely associated with unfavourable cardiovascular outcome and atherosclerosis. In this study we sought to determine the possible association between novel markers of subclinical inflammation and urinary albumin excretion rate (UAER), another index of increased cardiovascular risk, in essential hypertensive patients. The study population consisted of 62 newly diagnosed untreated non-diabetic patients with stage I to II essential hypertension [40 men, mean age⫽48 years, office blood pressure (BP)⫽144/95 mmHg]. Venous blood samples were drawn for estimation of C-reactive protein (CRP), serum amyloid A (SAA), macrophage chemoattractant protein-1 (MCP1), tumor necrosis factor (TNF)-alpha and myeloperoxidase (MPO), according to established techniques. Furthermore, UAER was determined in 3 non-consecutive 24h urine samples. For the pooled population, body mass index was 28.2⫾4kg/m2, left ventricular mass index was 99.5⫾23g/m2, UAER was 28.53⫾2 mg/24h, total cholesterol was 223.6⫾44 mg/dl, triglycerides were 136⫾38 mg/dl and low-density lipoprotein was 143⫾38 mg/dl. Regarding the inflammatory factors, CRP, SAA, TNF-alpha, MCP-1 and MPO levels were 2,29⫾0.2 mg/l, 6.05⫾0.6 mg/l, 7.3⫾0.7 pg/ml, 146.6⫾9 pg/ml and 0.48⫾0.02 U/ml, respectively. UAER was positively related to TNFalpha levels (r⫽0.28, p⬍0.05), systolic BP levels (r⫽0,30 p⬍0.05), total cholesterol (r⫽0.43, p⫽0.001) and low-density lipoprotein concentrations (r⫽0.45, p⫽0.001), while there was no correlation with CRP, SAA, MCP-1 and MPO values (p⫽NS). Additionally, TNF-alpha levels were associated with low-density lipoprotein plasma concentration (r⫽0.31, p⬍0.05). In conclusion, in uncomplicated newly diagnosed essential hypertension, among several novel inflammatory mediators, only TNF-alpha seems to be a rather sensitive marker of subclinical vascular dysfunction, at least at the level of renal glomerulus. In conjunction with UAER measurement, TNF-alpha may contribute to better cardiovascular risk stratification in this setting. Key Words: Urinary Albumin Excretion Rate, Inflammatory Markers, Essential Hypertension

P-156 NITRIC OXIDE SYNTHASE INHIBITION MEDIATED AFFERENT AND EFFERENT ARTERIOLAR VASOCONSTRICTION INVOLVES L-TYPE CALCIUM CHANNEL ACTIVATION Ming-Guo Feng, L. Gabriel Navar. Department of Physiology, Tulane University School of Medicine, New Orleans, LA.

Key Words: Phosphodiesterase, Salt, Dahl Rat

L-type Ca2⫹ channels are expressed in renal microvasculature, but There is less functional evidence regarding the role of L and T-type channels in regulating the NOS inhibition mediated vasoconstriction of afferent and efferent arterioles. Recently, NO have been implicated to affect voltagegated Ca2⫹ channel activity. To test the hypothesis that L-type Ca2⫹ channel may mediate afferent and efferent arteriole vasoconstriction following inhibition of nitric oxide synthase (NOS), videomicroscopic measurements of vascular dimensions were performed on the isolated blood-perfused juxtamedullary nephron preparation from Sprague-Dawley rats. Single afferent or efferent arterioles were superfused with solutions containing a NOS inhibitor, L-NNA or a L-type Ca2⫹ channel blocker, diltiazem or a T-type Ca2⫹ channel blocker, pimozide. L-NNA (100␮M) significantly decreased afferent and efferent arteriolar diameter

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by 19.6⫾3.0% (from 18.6⫾0.5 to 14.9⫾0.4 ␮m p⬍0.01) and 15.1⫾2.1% (from 19.0⫾0.4 to 16.1⫾0.6 ␮m p⬍0.01), respectively. However, L-NNA induced vasoconstriction was markedly inhibited by administration of 10␮M diltiazem, affrent and efferent arterioles with diameters increasing by 36.3⫾6.4 % (p⬍0.01) and 26.5⫾7.8% (p⬍0.01), respectively. In addition, adding 10␮M pimozide after diltiazem did not significantly augment the dilation of afferent and efferent arteriolar diameter. These results provide further evidence that NO may affect voltage-gated Ca2⫹ channels activity in afferent and efferent arterioles. The vasoconstriction elicited by NOS inhibition was blocked by diltiazem suggesting that the vasoconstriction involved activation of L-type Ca2⫹ channel in afferent and efferent arterioles. L-type Ca2⫹ channel may act cooperatively with T-type channels to mediate Ca2⫹ entry responsible for NOS inhibition mediated efferent and afferent arteriole vasoconstriction. L-type Ca2⫹ channel blockers may be of value in counteract endothelial dysfunction associated with hypertension and associated cardiovascular disorders. Key Words: Renal Microcirculation, Nitric Oxide Synthase, Ca2⫹ Channels

P-157 EFFECTS OF PERINDOPRIL, IRBESARTAN, AND PERINDOPRIL PLUS IRBESARTAN ON BLOOD PRESSURE, RENAL HEMODYNAMICS, PROTEINURIA, RENIN ANGIOTESIN-ALDOSTERONE SYSTEM, AND TGF-B1, IN TYPE 2 DIABETES WITH NEPHROPATHY Jorge Paulo Matos, Maria Lourdes Rodrigues, Debora Torres Valenc¸ a, Vagner Loba˜ o Ismerin, Claudio Sergio Lau, Sergio Girao Barroso, Edson Boasquevisque, Virginia Genelhu Abreu, Emilio Antonio Francischetti. Hypertension Clinic, Laboratory of Clinical and Experimental Pathophysiology - CLINEX, Rio de Janeiro State University, Rio de Janeiro, Rio de Janeiro, Brazil. The aim of this study was to evaluate the effects of the association of an angiotensin II receptor antagonist plus an ACE inhibitor on factors linked to the progression of renal disease in type 2 DM patients. Twenty patients with type 2 diabetes, proteinuria ⬎500 mg/24h and creatinine ⬍1.8 mg/dL were randomly assigned to be treated with perindopril 8 mg/day (P), irbesartan 300 mg/day (I) or a combination of irbesartan and perindopril at equivalent dose (P⫹I). Each treatment phase lasting 16 weeks was preceded by a 4-week wash-out period. Diuretics, clonidine and hydralazine were added in both treatment and wash-out periods seeking adequate blood pressure control. Patients were evaluated at baseline and at the final period of each treatment phase. The following parameters were assessed: Ambulatory monitoring BP, glomerular filtration rate [GFR (51Cr-EDTA)], effective renal plasma flow [ERPF(131Ihippuran)], plasma renin and aldosterone, proteinuria, and urinary TGF-␤1 excretion. Fifteen patients completed all the phases. Use of P, I and P⫹I leaded to a slight reduction in mean blood pressure of 6 mmHg, 4 mmHg and 4 mmHg, respectively. Changes in GFR and ERPF were not significant in any phase. Treatment with both I and P⫹I induced similar plasma renin elevation,’ but treatment with P did not suggesting escape. Aldosterone was reduced only by treatment with P⫹I (97 vs. 62 pg/mL; p⫽0.02). Proteinuria was significantly reduced with P (829 vs. 545 mg/24 h; p⫽0.03) and P⫹I (966 vs. 644 mg/24h; p⫽0.01) but not with I (867 vs. 701mg/24h; p⫽0.41). Urinary TGF␤1 excretion did not change with P alone but was significantly reduced with both I (⫺47%; p⫽0.024) and P⫹I (⫺44%; p⫽0.041). Use of P⫹I was associated to hematocrit decline (36.6% vs. 34.2%; p⫽0.002) and a trend to rise in serum K⫹ (4.3 vs. 4.7mEq/L; p⫽0.11). In conclusion, dual blockade of angiotensin II with irbesartan plus perindopril reduced plasma aldosterone, proteinuria and urinary TGF␤1. Key Words: Diabetes, Proteinuria, Renin-Angiotensin-Aldosterone System

POSTERS: Kidney and Hypertension

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P-158 HDL MEDIATES REVERSE CHOLESTEROL TRANSPORT FROM MESANGIAL CELLS VIA MAP KINASE Siddhartha S Ghosh, Shobha Ghosh, Todd WB Gehr, Domenic A Sica. Int Medicine, VCU Medical Center, Richmond, VA. Reverse transport of cholesterol from peripheral tissue to the liver is one of the mechanisms by which HDL provides cardioprotective action. We provide evidence that HDL plays a major role in cholesterol efflux from lipid loaded mesangial foam cells, which function to facilitate reverse cholesterol transport and alleviate experimental glomerulosclerosis. In this study, we explored the role of HDL not only as a cholesterol acceptor, but also in its cell signaling role, which affects the ratio of cholesterol influx/efflux. Methods: To determine the effects of HDL-mediated signaling on influx pathways, the expression of scavenger receptor CD36 in response to HDL-mediated activation of MAP kinase was monitored by Western Blot Analysis. HDL-mediated cholesterol efflux from [3H]-cholesterol labeled and acetylated LDL loaded mesangial cells were also examined. The effect of the HDL and MAP kinase inhibitor, 20␮M PD98059 (PD) on cytoplasmic lipid droplet mobilization was monitored to evaluate the role of HDL-mediated signaling on cellular cholesterol efflux. Results: Addition of HDL (2␮g/ml-1 mg/ml) dose dependently increased the efflux of cholesterol from messangial cells. Cholesterol efflux in the presence of 100 ␮g/ml HDL was measured at 4, 8 and 24 hours (16⫾1.03%, 28⫾2% and 61⫾3% respectively, p⬍0.05). PD (20␮M) blocked HDL mediated efflux. This suggests HDL promotes cholesterol efflux via MAP Kinase. Addition of HDL to mesangial cells causes increased ERK phosphorylation (p⬍0.01) which was blocked by 20␮M PD. HDL (50 and 100 ␮g/ml) increased phosphorylation of PPAR␥ by 18⫾ 1.5% and 30⫾ 8.5% respectively and MAPK inhibitor PD(20␮M) inhibited phosphorylation. Furthermore, phosphorylation of PPAR␥ decreases transcription of PPAR target genes such as CD36. It has been demonstrated that the scavenger receptor CD 36 is responsible for LDL uptake. HDL down-regulated CD36 expression and this effect was blocked by PD. This implies that HDL increases efflux via ERK and erodes cholesterol influx pathways directly by decreasing CD36 expression and indirectly by down regulating PPAR␥ and thereby decreasing transcription of CD36. Our data demonstrates HDL increases cholesterol efflux from mesangial cells, mobilizes intracellular lipid via MAP kinase and functions as a critical signaling molecule, which may have important implications for targeting HDL-concentrations for treatment in conditions characterized by glomeruloscerosis and/or left ventricular hypertrophy. Key Words: Efflux, PPAR, CD 36

P-159 PROGNOSIS IN HEMODIALYSIS PATIENTS WITHOUT CARDIAC DYSFUNCTION: HIGH LEVELS VERSUS LOW LEVELS OF BRAIN NATRIURETIC PEPTIDE Yuji Hara, Akiyoshi Ogimoto, Tomoaki Ohtsuka, Yuji Shigematsu, Jitsuo Higaki. Second Department of Internal Medicine, Ehime University, Onsen-gun, Ehime, Japan. Background: Cardiovascular events are the major determinant of the prognosis in hemodialysis patients. In this study, we investigated whether plasma levels of brain natriuretic peptide (BNP) predict cardiac events in hemodialysis patients without cardiac dysfunction. Methods: Forty-seven patients without cardiac dysfunction were enrolled in accordance with echocardiographic study. Echocardiographic study and measurement of BNP were performed at baseline. The patients were stratified into two groups on the basis of median plasma concentration of BNP (90pg/ml): low levels of BNP (BNP ⬍90pg/ml; n⫽24) and high levels of BNP (BNP ⱖ90pg/ml; n⫽23). Thromboembolism,