Loss of renal blood flow autoregulation in chronic glomerulonephritic rats

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.