Effect of Theophylline and Adrenergic Blocking Drugs on the Renin Response to Norepinephrine In Vitro

The effects of norepinephrine, theophylline, and adrenergic blocking drugs on renin release from rat kidney slices were studied in vitro. l -Norepinephrine increased renin release into the incubation medium; this increase was accompanied by an increase in the renin content of the slices. Statistically significant increases in renin release were produced by 10 -5 M and 2 x 10 -5 M l -norepinephrine. d -Norepinephrine in the same doses was ineffective. Theophylline (10 -3 M ) had no effect by itself, but it potentiated the effect of l -norepinephrine on renin release. The response to l -norepinephrine was markedly suppressed by l -propranolol (10 -4 M ) but not by d -propranolol (10 -4 M ). The α-receptor blocking agents phentolamine (10 -4 M ) and phenoxybenzamine (10 -4 M ) increased rather than decreased the effect of l -norepinephrine. These results are consistent with a direct intrarenal effect of norepinephrine on renin release; this effect appears to be mediated by a β-adrenergic mechanism.