Renin-angiotensin system inhibition reduces glycine-induced glomerular hyperfiltration in conscious rats

Abstract

It has been reported that high protein intake or amino acid infusion-induced glomerular hyperfiltration are accompanied by an elevation of plasma renin activity and renal renin mRNA. We therefore investigated the effect of inhibition of the renin-angiotensin system by SK&F 108566, a novel, nonpeptide angiotensin II (AII) receptor antagonist, or by enalapril, an angiotensin converting enzyme inhibitor, on glycine-induced hyperfiltration. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured by inulin and p-aminohippurate clearances in conscious chronically instrumented rats. Glycine infusion (3.7 mg/min i.v.; n = 8) significantly increased GFR by 27% (from 1.09 +/- 0.53 to 1.38 +/- 0.08 ml/min.100 g), ERPF by 22% (2.96 +/- 0.30 to 3.61 +/- 0.32 ml/min.100 g) and significantly decreased effective renal vascular resistance by 22% [from 25.4 +/- 2.9 to 20.8 +/- 2.5 mm Hg/(ml/min.100 g)]. SK&F 108566 (30 micrograms/kg.min) or enalapril (1 mg/kg), at doses which inhibited the pressor effects of AII or AI, respectively, but had no significant influence on base-line GFR and ERPF, significantly attenuated the glycine-induced glomerular hyperfiltration and hyperemia. In the presence of SK&F 108566 or enalapril, glycine resulted in only small, statistically insignificant changes in GFR (from 1.07 +/- 0.03 to 1.10 +/- 0.04 and from 1.19 +/- 0.03 to 1.21 +/- 0.08 ml/min.100 g, respectively), ERPF (from 3.27 +/- 0.21 to 3.53 +/- 0.26 and from 3.57 +/- 0.11 to 3.41 +/- 0.38 ml/min.100 g, respectively) and effective renal vascular resistance [from 21.2 +/- 1.9 to 19.2 +/- 1.6 and from 18.4 +/- 0.9 to 20.2 +/- 2.2 mm Hg/(ml/min.100 g], respectively).(ABSTRACT TRUNCATED AT 250 WORDS)