Impaired Autoregulation of Blood Flow and Glomerular Filtration Rate in the Isolated Dog Kidney Depleted of Renin

Abstract

The effect of renin depletion on autoregulation of renal blood flow and glomerular filtration rate was examined in an isolated perfused kidney preparation. Group 1 dogs received a normal-sodium diet, group 2 dogs received deoxycorticosterone acetate (DOCA) and a high-sodium diet, group 3 dogs received DOCA and a sodium-deficient diet, group 4 dogs received a high-sodium diet without DOCA, and dogs in groups 5 and 6 were treated just like dogs in groups 1 and 2, respectively. Renin release was stimulated by decreasing renal arterial pressure to 50 mm Hg. An increase in renal arterial pressure from 100 to 160 mm Hg was associated with an impaired autoregulatory response in kidneys from group 2 dogs and in two kidneys from group 4 dogs; these kidneys exhibited suppressed or absent renin release in response to a decrease in renal arterial pressure. A separate group of experiments demonstrated that DOCA plus a high-sodium diet completely depleted the kidney of renin stores, indicating that decreased renin secretion reflected depletion of renal renin content. Infusing angiotensin II (0.22 ± 0.06 µg/min) into the renal artery of group 2 kidneys did not normalize the autoregulatory response. A decrease in renal arterial pressure from 150 to 50 mm Hg was associated with impaired autoregulation of glomerular filtration rate and renal blood flow in kidneys from group 6 dogs; renin secretion was undetectable in these kidneys. All kidneys from groups 1, 3, and 5 and the remaining six kidneys from group 4 exhibited a normal autoregulatory response and normal renin release. In groups 1-3, zonal blood flow was measured using the radiolabeled microsphere technique. Only in group 2 did a significant redistribution of fractional blood flow from the inner to the outer cortex occur. These experiments demonstrate that renin depletion impairs the capacity of the kidney to autoregulate blood flow and glomerular filtration rate; thus the data are consistent with the hypothesis that the renin-angiotensin system participates in the autoregulatory response.