The Effects of Dopamine on Renin Releasein Vitro

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Abstract
To examine the direct effects of dopamine on renin release, the in vitro rat kidney slice system, devoid of hemodynamic and humoral effects, was chosen. In the presence of an antioxidant, ascorbic acid (6 .times. 10-4 M), a significant dose-related stimulation of renin release was observed with addition of 10-5 M and higher concentrations of dopamine. When the monoamine oxidase inhibitor, pheniprazine (1 .times. 10-5 M) was added, significant, dose-related stimulation of renin release was observed with 10-8 M and higher concentrations of dopamine. Dopamine-induced renin release was not inhibited by the presence of the .alpha.-adrenergic antagonist, phentolamine (9 .times. 10-4 M), the dopaminergic antagonist, haloperidol (5 .times. 10-5 M) or the neural uptake inhibitor, cocaine (1 .times. 10-5 M). The presence of the .beta.-adrenergic antagonist, propranolol (2 .times. 10-4 M) completely inhibited dopamine-induced renin release. Dopamine can directly stimulate renin release in the absence of effects of hemodynamic factors, alterations in Na metabolism or release of endogenous adrenergic agents. This direct effect of dopamine on renin release appears to be mediated by an agonistic effect on the juxtaglomerular .beta. receptor rather than by the presence of a specific dopaminergic receptor for renin release.