Catecholamine-dependent cyclic adenosine monophosphate and renin in the dog kidney

Role of cyclic AMP in the regulation of renin release from the isolated perfused rat kidney

The role of cyclic AMP in the regulation of renin release (RR) was studied in isolated rat kidneys, which were perfused at constant pressure in a single-pass system with a modified Krebs-henseleit solution. Isoproterenol (IP) (2 x 10(-9) to 2 x 10(-6) M) and 3-isobutyl-1-methyl-xanthine (IBMX) (4 x 10(-7) to 7 x 10(-5) M) induced a dose-dependent increase of renal perfusate flow, glomerular filtration rate and urinary sodium excretion. RR was stimulated up to 10-fold above control values within 5 min. At the lowest concentrations IP stimulated RR, but did not affect renal haemodynamics. When IP and IBMX were administered concomitantly, a supraadditive stimulation of RR was observed. Dibutyryl-cAMP (db-cAMP) and 8-Br-cGMP (10(-6) to 10(-4) M) produced a similar dose-dependent vasodilation and natriuresis, but differed in their action on RR. Within 15 min after the start of the infusion, db-cAMP increased RR up to 4-fold, whereas 8-Br-cGMP was without an effect. These results suggest that IP, IBMX and db-cAMP stimulated RR by increasing the concentrations of cAMP in the epitheloid cells and independently of changes in renal haemodynamics and sodium excretion.

Control of renin release: a review of experimental evidence and clinical implications

Present knowledge of the mechanisms regulating release of renin is reviewed with particular emphasis on neural factors. Evidence is given for a direct effect of renal innervation on beta adrenergic receptors in juxtaglomerular cells, and for the involvement of reflex release of renin in conditions such as tilting and acute salt depletion. Participation of neural and nonneural mechanisms of control is also shown to occur in other conditions, such as aortic constriction and hemorrhage. The view is held that neural sympathetic factors might explain some of the renin disturbances found in essential hypertension. First, in patients with high renin hypertension part of the hypertension is renin-dependent, and these pressor levels of renin seem to be neurally induced since they can commonly be suppressed by beta adrenoreceptor blocking agents. Second, the hypothesis is presented that patients with low renin hypertension, at least those who have no volume disturbance, have a blunted sympathetic control of renin release. Therefore a sufficiently precise test of sympathetic activity, and possibly of body fluid volumes, should be associated with renin profiles for a better understanding of the pathophysiology of arterial hypertension and as a better guide to therapeutic management. Indeed, most of the available antihypertensive drugs act on sympathetic activity, body fluid volume or renin, and this multifaceted profile would provide more rational guidelines for treatment.