Dissociation of renal blood flow and filtration rate autoregulation by renin depletion

Abstract

Renal blood flow (RBF) and glomerular filtration rate (GFR) autoregulation during changes in renal artery pressure (RAP) were examined in dogs fed a "normal" diet (group 1, n = 10) and in renin-depleted dogs (group 2, n = 11) which received a high-sodium diet and deoxycorticosterone acetate (DOCA) injections for a minimum of 21 days prior to the study. Renal venous plasma renin activity was undetectable in group 2 by radioimmunoassay of angiotensin I and did not increase even when RAP was reduced to less than 70 mmHg. Autoregulation of RBF was not impaired by renin depletion. However, GFR autoregulation, which was very effective in group 1 dogs, was markedly impaired in group 2. Average GFR in group 2 decreased progressively to 58 +/- 7% of the control value as RAP was reduced in steps from the control value of 137 +/- 3 to 69 +/- 1 mmHg. In normal dogs, the filtration fraction either increased slightly or did not change when RAP was reduced in steps, whereas in renin-depleted dogs the filtration fraction decreased progressively during reductions in RAP. Thus, chronic sodium loading and DOCA administration causes renin depletion and dissociates the autoregulation of RBF and GFR. These data are consistent with the hypothesis that the renin-angiotensin system participates in the control of GFR, possibly by an efferent arteriolar mechanism.