Effects of labetalol on renin release from rat kidney cortical slices

Effects of labetalol, a combined alpha- and beta-adrenoceptor blocking agent, on the changes in renin release in response to isoproterenol or norepinephrine were examined in comparison with those of propranolol and prazosin, using rat kidney cortical slices. Isoproterenol (10(-9) to 10(-5) M) produced a dose-related increasing effect on renin release from the slices, although the increased release was markedly attenuated by the higher dose (10(-4) M). On the other hand, norepinephrine, at relatively higher concentrations (over 10(-6) M), caused a significant decreasing action on the release. Labetalol alone (10(-9) to 10(-4) M) had no effect on basal renin release. However, the agent exerted a concentration-dependent blocking action on the renin response to 10(-6) M isoproterenol. Similar results were observed with propranolol. The decreased response of renin release to 10(-5) M norepinephrine was significantly inhibited by labetalol over 10(-6) M. Labetalol, at a concentration of 10(-5) M, abolished the decreased release by 10(-5) M norepinephrine. On the other hand, the decreasing effect of 10(-5) M norepinephrine was substantially reversed rather than abolished by prazosin over 10(-7) M. These results indicate that labetalol inhibited the response of renin in rat kidney cortical slices, by beta- and alpha 1-adrenoceptor antagonistic action, respectively.