Renal Hemodynamics and Plasma Renin Activity after Renal Artery Constriction in Conscious Dogs

Renal hemodynamics and plasma renin activity were studied during acute and chronic renal artery constriction produced by an externally controlled snare in conscious dogs. Renal vascular resistance immediately decreased, then increased to a level above control after approximately 1 hour, and continued to increase until the second day after constriction. Total renal flow rate was unchanged in the first hour, decreased in the second hour, and decreased further between the first and the second day after constriction. Renal artery pressure distal to the snare increased after the initial stenosis but remained below the control level. Changes in renal artery pressure were dependent primarily on renal vascular resistance rather than on aortic blood pressure. Analysis of ""Xe-clearance curves showed that the fractional weight of and the fractional flow to the fastest-clearing compartment decreased after the first hour and decreased further between the first and the second day after constriction. Plasma renin activity rose immediately, began to drop on the first day after constriction, and was essentially normal by the second day. No parameter changed significantly after the second day, and no hemodynamic factor was consistently correlated with changes in plasma renin activity. These results do not confirm an apparent correlation between renal vasodilation and renin release reported in an earlier study.