ARTICLES

Circulating epinephrine stimulates renin secretion in anesthetized dogs by activation of extrarenal adrenoceptors

The present experiments were designed to determine the location of the adrenoceptors responsible for initiating epinephrine-induced stimulation of renin secretion in vivo. Three hypotheses were tested: 1) the receptors are located intrarenally, 2) the receptors are located extrarenally , and 3) an interaction exists between intrarenal receptors and some event initiated by extrarenal receptors. All experiments were conducted in anesthetized dogs surgically prepared for renal clearance studies. Intravenous infusion of epinephrine at 250 ng X kg-1 X min-1 increased one-kidney renin secretion rate more than fivefold. In contrast, direct intrarenal infusion of epinephrine at 25 ng X kg-1 X min-1 only doubled renin secretion rate from the infused kidney. In six animals in which renin secretion rates were measured bilaterally during intrarenal epinephrine infusion, no differences in renin secretion rates were detected between the two kidneys. To examine the hypothesis that an interaction exists between intrarenal and extrarenal adrenoceptors, epinephrine was infused intravenously at 25 ng X kg-1 X min-1 and simultaneously into one renal artery at 10 ng X kg-1 X min-1. Renin secretion rates rose significantly (P less than 0.01) but equally from both kidneys. At lower epinephrine infusion rates (10 ng X kg-1 X min-1 intravenously plus 3 ng X kg-1 X min-1 intrarenally), renin secretion rates increased submaximally but still equally from both kidneys. It is concluded that epinephrine-induced stimulation of renin secretion in vivo is initiated by adrenoceptors located only extrarenally .