Control of Renln Secretion

• The nature of the stimulus that causes kid-neys to release renin has not been established with certainty. It has been assumed by many that ischemia is a logical cause, while others have concluded that a hemodynamic change is responsible. Several hypotheses have been based on a suggestive, but unproven, correla-tion between degree of granulation of the juxtaglomerular apparatus and rate of secre-tion of renin. (For review see Braun-Menen-dez et al.,1 Tobian,2 and Page and McCub-bin.3) During experiments which demonstrated that renin is released primarily into renal venous blood rather than renal lymph,4 it was noted that renin secretion increased during rather small reductions in renal perfusion pres-sure that were not likely to cause renal ischemia. This observation was pursued and preliminary experiments5 indicated that renin could be released during reduction in renal perfusion pressure without change in total renal blood flow. A renal baroreceptor mecha-nism was postulated to control renin secretion. The present experiments examine the be-havior of this baroreceptor more fully and investigate the effects of a variety of other stimuli on renin secretion. Methods Thirty fasting mongrel dogs weighing 10 to 20 kg were anesthetized with morphine sulphate (2 mgAg sc) and sodium pentobarbital (15 mg/kg rv). Through a flank incision the left renal pedicle was exposed and a noncannulatin