Loss of renal blood flow autoregulation in chronic glomerulonephritic rats

Abstract

Autoregulation of renal blood flow (RBF) was investigated in subacute (2 mo) and chronic (18 mo) passive Heymann nephritis (PH-2, PH-18) and age-matched controls (C-2, C-18). RBF was significantly lower in PH-18 than in C-18 (3.7 +/- 0.4 vs. 4.7 +/- 0.5 ml.min-1.kidney-1; P less than 0.05), whereas the mean blood pressure (MAP) was similar. The creatinine clearance was significantly lower in PH-18 than in C-18 (1.89 +/- 0.5 vs. 3.15 +/- 0.77 ml.min-1.kg body wt-1; P less than 0.002). Kidney weight was significantly higher in PH-18 than in C-18 (P less than 0.002). In PH-2 and C-2, RBF, MAP, creatinine clearance, and kidney weight were not different (P greater than 0.10). In PH-18 the maximal reduction of the renal vascular resistance (RVR) during RBF autoregulation was 4 +/- 2%, compared with 24 +/- 4% in C-18 (P less than 0.002); the lower pressure limit of RBF autoregulation was 131 +/- 9 vs. 85 +/- 4 mmHg (P less than 0.002). In PH-2 the maximal reduction of RVR during RBF autoregulation was 18 +/- 3%; in C-2 it was 25 +/- 2% (P greater than 0.10); the lower pressure limit of RBF autoregulation was 101 +/- 4 vs. 84 +/- 6 mmHg (P less than 0.02). It is concluded that RBF autoregulation is nearly lost in the late stage of glomerulonephritis, possibly as a consequence of the nephron loss.