Relationship between renin secretion and renal autoregulation in the dogs

The present investigation examined the relationship between renin release and renal autoregulation of blood flow in the anesthetized dogs. A reduction in renal arterial pressure from control pressure to 100mmHg changed neither the flow rates of all cortex zones nor renin secretion. Further reductions of renal arterial pressure to 70mmHg and 50mmHg resulted in a significant increase of renin secretion and a decrease of blood flow in the outer cortex. Intrarenal arterial infusion of acethylcholine abolished an autoregulation of blood flow and pressure reduction to 100mmHg during acetylcholine infusion resulted in a marked increase of renin secretion without any further change in afferent arteriolar resistance. Intrarenal arterial infusion of norepinephrine at a control pressure increased a renin release. However, norepinephrine infusion at reduced pressure suppressed the renin release with recovery a vascular resistance to the control level. These results suggest that the changes in the degree of blood flow and pressure in the renal afferent arterioles are not essential for the renin release, but renin release by the pressure reduction might be related to the autoregulatory capapcity of afferent arterioles in the outer cortex.