Intrarenal control of electrolyte excretion by angiotensin II

Abstract

The intrarenal role of angiotensin II in regulating renal blood flow and glomerular filtration rate, as well as water and electrolyte excretion, was examined in 5 normal and 17 Na-depleted dogs. In the Na-depleted dogs, intrarenal infusion of the competitive antagonist [Sar1,Ile8]-angiotensin II (0.25 .mu.g/kg per min) elicited marked increases in renal blood flow, urine flow, urinary Na, K and osmolar excretion, smaller increases in glomerular filtration rate and small but significant reductions in mean systemic arterial pressure. The rise in urinary Na excretion from 0.087 .+-. 0.02 during the control period to 0.380 .+-. 0.110 meq/min per gram kidney wt after 90 min of antagonist infusion appeared to be due to the intrarenal effects of angiotensin II blockade, since there were no consistent changes in plasma aldosterone concentration during antagonist infusion. In a series of Na-depleted dogs which serve as a time control, there were no significant changes in any of the variables studied. Intrarenal infusion of the antagonist (0.25 .mu.g/kg per min) in normal dogs resulted in small but significant increases in renal blood flow and urinary Na, K and osmolar excretion. Angiotensin probably plays an important role in regulating renal hemodynamics and electrolyte excretion, especially when the renin-angiotensin system is activated by Na depletion.