Alpha adrenergic-mediated renin release is prostaglandin-dependent

The contribution of the alpha adrenergic receptor activation to the sympathetic mediated renin release was examined by utilizing intrarenal phenylephrine infusion in beta adrenergically blocked anesthetized mongrel dogs. Increasing doses of intrarenal phenylephrine resulted in a dose-dependent decrease in renal blood flow, a dose-dependent decrease in urinary excretion of sodium and a stimulation of renal renin release which was not dose-dependent. The effect of intrarenal phenylephrine on renin release was totally abolished by pretreating the dogs with indomethacin, even though neither the vasoconstriction nor the decrement in urinary sodium excretion was altered by the drug. In addition, intrarenal phenylephrine did not elicit renal renin release in dogs with kidneys that were rendered nonfiltering. These data are consistent with the hypothesis that exogenous renal alpha adrenergic stimulation in the dog contributes to renin release through the prostaglandin system and that the stimulation of the macula densa mechanism is responsible for the major effect of phenylephrine on renin release.