Effect of intravenous epinephrine infusion on plasma renin activity in adrenalectomized dogs

Previous experiments have shown that circulating epinephrine stimulates renin secretin and increases plasma renin activity (PRA) when it is infused intravenously, but not when it is infused directly into the renal artery at similar infusion rates. The present experiments were designed to test the hypothesis that the adrenal glands mediate the PRA response to intravenous epinephrine infusion. Accordingly, anesthetized dogs were prepared with either an acute bilateral adrenalectomy or a sham-adrenalectomy procedure. Epinephrine was then infused intravenously into each animal for 45 minutes at a rate of 25 ng X kg-1 X min-1. Time control experiments in which epinephrine was not infused were also conducted. In sham-adrenalectomized dogs, PRA (in nanograms per ml h-1) rose from 4.1 +/- 1.4 in the control period to 13.0 +/- 3.0 during intravenous epinephrine infusion (means +/- SE; p less than 0.01). In adrenalectomized dogs, PRA rose from 2.1 +/- 0.4 during the control period to 5.5 +/- 0.9 during intravenous epinephrine infusion (p less than 0.01). Neither the absolute increments in PRA nor the percent increases in PRA were significantly different between the two groups receiving epinephrine. PRA remained unchanged in time control experiments. These data demonstrate that the adrenal glands need not be present in order for intravenous epinephrine infusion to elicit an increase in PRA. The data do not support the hypothesis, therefore, that epinephrine-induced increases in PRA are initiated by receptors located within the adrenal glands.