A biphasic effect of noradrenaline on renin release from rat juxtaglomerular cells in vitro is mediated by alpha 1- and beta-adrenoceptors.

Abstract

The direct effect of noradrenaline on renin release from juxtaglomerular (JG) cells in vitro were investigated in a dynamic superfusion system of dispersed rat renal cortical cells. At low concentrations (1-100 nmol/l), noradrenaline stimulated renin release in a dose-dependent manner, while at higher concentrations (0.1-1 mmol/l) it inhibited renin release. The stimulatory effect of 0.1 mumol noradrenaline/l was completely blocked by a beta-adrenoceptor antagonist, propranolol (0.1 mumol/l). When applied at concentrations of 1 mumol/l or 10 mumol/l, noradrenaline had no consistent effect on renin release, although 10 mumol noradrenaline/l had an inhibitory effect in the presence of propranolol (0.1 mumol/l). The inhibitory effect of noradrenaline (0.1 mmol/l) was converted to a stimulatory effect by the addition of an alpha 1-adrenoceptor antagonist (bunazosin, 1 mumol/l), but was not altered by the addition of an alpha 2-adrenoceptor antagonist (yohimbine, 1 mumol/l). These results indicate that low concentrations of noradrenaline directly stimulate renin release from JG cells by the activation of beta-adrenoceptors, while high concentrations of noradrenaline inhibit renin release by the activation of alpha 1-adrenoceptors. Accordingly, a dynamic balance may exist between beta-adrenergic stimulation and alpha 1-adrenergic depression of renin release.