Goldblatt hypertension in rats: a model for unilateral renal artery stenosis in man

Determinants of glomerular ultrafiltration were studied by micropuncture in clamped (n = 11) and unclamped (n = 7) kidneys of two-kidney hypertensive rats and compared to 15 controls. Infusion of the angiotensin II antagonist and saralasin lowered the blood pressure significantly. Glomerular capillary pressure (PGC) in clamped kidneys was decreased to 56 +/- (SD) 3 vs. 61 +/- 3 mm Hg in controls. Early proximal flow rate (EPFR) was decreased to 20 +/- 1 vs. 26 +/- 2 nl/min in controls, at an unchanged single nephron filtration fraction (SNFF), indicating a reduced glomerular plasma flow (SNGPF). Preglomerular resistance (RA) was increased by 21%. In unclamped kidneys PGC was increased to 65 +/- 2 mm Hg. EPFR was increased to 32 +/- 2 nl/min, indicating, at an unchanged SNFF, an increased SNGPF. RA increased by 51%, whereas postglomerular resistance declined by 25%. The ultrafiltration coefficient was reduced by 24% in unclamped kidneys. Our results indicate that in clamped kidneys an increase of RA causes a reduction of PGC and hence a reduction of pressure at the baroreceptor site which may act as a trigger mechanism for renin release.