The different effects of exogenous and neuronally released norepinephrine on renin release in rat kidney cortical slices

Stimulatory effects of neuronally released norepinephrine on renin release from rat kidney cortical slices

Stimulatory effects of extracellular high K+ in the presence of nifedipine (NIF) on renin release (RR) from kidney cortical slices were investigated. The stimulation was suppressed either by propranolol or by metoprolol but not by prazosin. High K+ plus NIF-induced increase in RR was attenuated by renal denervation. The enhancing effect was not observed when the slices were incubated in Ca2+-free buffer or in medium containing divalent cations such as Cd2+, Co2+ and Mn2+. These alterations in RR correlated with 3H-efflux from the slices preloaded with 3H-norepinephrine. We conclude that the high K+ plus NIF-induced increase in RR from the slices is mediated by norepinephrine (NE) derived from renal sympathetic nerves and that this neuronally released NE stimulates RR via the activation of beta-adrenoceptors.

Renin release in anesthetized rats is enhanced by the calmodulin antagonist W-7

In foregoing work, we found that the release of renin from rat kidney cortical slices was stimulated by the calmodulin antagonist W-7. The present work was done to determine whether W-7 would stimulate renin release in vivo. W-7 and its control agent, W-5 were directly infused into the renal artery of anesthetized rats. W-7 and W-5, at 50 micrograms/kg/min, produced no significant effects on renin release. Infusion of W-7 at 100 micrograms/kg/min resulted in a marked stimulation of renin release, but there was no significant alteration in the release when the same dose of W-5 was infused. Both compounds elicited a slight decrease in renal blood flow. The alterations in renin release and renal blood flow seen with W-7 were not affected by pretreatment with phentolamine or propranolol. As W-7 stimulates renin release in vivo, the hypothesis that Ca2+-calmodulin plays an inhibitory role in renin release from the kidney is given added support.

Adrenoceptors in the kidney: localization and pharmacology

The kidney plays a key role in the regulation of blood pressure. The sympathetic nervous system can influence many aspects of kidney function in relation to blood pressure control, e.g. renal vascular tone, intrarenal renin release and tubular reabsorption of electrolytes and fluid. The intrarenal distribution of adrenoceptors has now been studied on the basis of modern receptor ligand binding techniques combined with microscopic studies. The preferential localization of each adrenoceptor subtype within the kidney is reviewed. Furthermore, an attempt is made to describe the functional correlation of the presence of different adrenoceptor subtypes. Finally, the possible role of renal adrenoceptor abnormalities in the pathogenesis of hypertension is discussed.