Effects of alpha-agonist on renin and prostaglandin E2 release in anesthetized dogs.

The relationship between renin release and renal prostaglandin (PG) production induced by the alpha-agonists methoxamine and alpha-methylnorepinephrine was examined in anesthetized dogs. Both intrarenal infusions of methoxamine (1, 3, and 5 micrograms/min) and alpha-methylnorepinephrine (0.37, 1, and 2 micrograms/min) resulted in a dose-dependent decrease in renal blood flow to a slight degree. Methoxamine dose-dependently increased the renin secretion rate but failed to increase the PGE2 secretion rate. In contrast, alpha-methylnorepinephrine failed to affect the renin secretion rate but dose-dependently increased the PGE2 secretion rate. The effect of methoxamine (5 micrograms/min) on renin release was abolished by the intrarenal alpha 1-adrenoceptor blockade with prazosin (3 micrograms/min) but was not affected by the intrarenal alpha 2-adrenoceptor blockade with yohimbine (30 micrograms/min). The effect of alpha-methylnorepinephrine (2 micrograms/min) on PGE2 release was abolished by yohimbine but not by prazosin. These results suggest that there is a dissociation between renin release and renal PG production induced by alpha-agonists and that renal alpha 1- and alpha 2-adrenoceptors may participate in renin and PGE2 release, respectively.