Actions de la noradrénaline et de l'ocytocine sur le transport actif de sodium et la perméabilité à de la peau de grenouille. Rôle du 3′,5′-AMP cyclique

Abstract

The acutions of noradrenalin and oxytocin on short-circited current, unidirectional rectional fluxes of Na + and Cl −, and water permeability of the isolated frog ( Rana esculenta) skin are compared. The results show that noradrenalin (10 −8 to 10 −6M) produces, like oxytocin (1) a stimulation of active Na + transport resulting from an increase of Na + influx without any modification of Na + outflux or of the two unidirectional fluxes of Cl −; (2) an increase in osmotic water permeability. At a much higher concentration (10 times higher than those producing a maximal stimulation of active Na + transport) noradrenalin produces a large increase in the permeability of the skin for both Na + and Cl − which is similar to those described by several authors. 3′,5′-Cyclic AMP and theophylline (10 −3 to 10 −2 M) mimic the action of oxytocin and of noradrenalin. Their potentiation by theophyllin suggests a common mechanism of action for these two hormones involving 3′,5′-cyclic AMP as an intermediate. However, the lack of activity of noradrenalin on the bladder, the different time course of the actions of noradrenalin and oxytocin on the skin, the inhibition of the actions of noradrenalin by dichloroisopropylarterenol while the actions of oxytocin are maintained show that the receptors for catecholamines and neurohypohysial hormones within the skin are different.