[Involvement of vasopressin in the effects of aldosterone on the arterial wall].

We have previously shown that an humoral factor is involved in the delayed effect of aldosterone on the passive transmembrane movements of Na+ from arterial smooth muscle (Moura and Worcel, 1984). In absence of vasopressin, the effects of aldosterone on the same Na transports suggest that vasopressin may be this humoral factor (Moura, Angeli and Worcel, 1986) (Angeli, Moura and Worcel, 1986). We show here that the s.c. injection of aldosterone (10 micrograms/kg) to adrenalectomized Sprague Dawley rats induces a release of vasopressin. This peptide exerts a direct action on ouabain-sensitive and insensitive components of 22Na efflux from the rat tail artery, and potentiates the late effect of aldosterone on passive Na+ efflux. There is no additive effect of the two hormones on Na+ pump activity. In conclusion vasopressin is the humoral factor involved in the late effect of aldosterone on passive transmembrane movement of Na from vascular smooth muscle.