The effect of acute angiotensin II blockade on renal function in rats with reduced renal mass.

The effect of acute Ang II blockade on renal function in rats with reduced nephron number was assessed in micropuncture studies. The Ang II receptor blocker, losartan, was administered at a dose of 10 mg i.v. at two intervals following five-sixths renal ablation. At eight weeks following ablation, Ang II blockade (Ang IIX) increased sodium excretion [UNa V, Ang IIX 2.2 +/- 0.4 microEq/min; time control (TC) 1.0 +/- 0.3 microEq/min; P < 0.05] but did not reduce mean arterial pressure (AP, Ang IIX 142 +/- 6 mm Hg; TC 151 +/- 6 mmHg), glomerular transcapillary pressure (delta P, Ang IIX 50 +/- 1 mm Hg; TC 50 +/- 1 mm Hg), or urine albumin excretion (UAlb V: Ang IIX 149 +/- 18 micrograms/min; TC 168 +/- 20 micrograms/min). Similarly, at two weeks following ablation, Ang II blockade increased UNa V (Ang IIX 2.8 +/- 0.4 microEq/min; TC 0.5 +/- 0.2 microEq/min; P < 0.05) without reducing AP (Ang IIX 132 +/- 6 mm Hg; TC 140 +/- 7 mm Hg), delta P (Ang IIX 50 +/- 3 mm Hg; TC 48 +/- 2 mm Hg), or UAlb V (Ang IIX 32 +/- 3 micrograms/min; TC 36 +/- 10 micrograms/min). These findings indicate that within the remant kidney, Ang II promotes sodium retention but does not have an acutely reversible effect on glomerular pressure or permselectivity.