[Changes in the contractile activity of the portal vein of the rat in response to corticosteroid hormones].

Corticosterone (8 X 10(-8) g/ml) augmented the amplitude of the rat portal vein phasic contractions within first minutes. The dose 5 X 10(-7) g/ml first augmented and then reduced the amplitude, simultaneously increasing the rate of autorhythmic activity and the vascular tone. Hydrocortisone and dexamethasone exerted no initial effect but reduced the amplitude of phasic contractions within 5-10 min. Glucocorticoids did not affect the rate of contractions, but dexamethasone (5 X 10(-7) g/ml) augmented the vascular tone. The mineral and glucocorticoid action of corticosteroids seems to be actualized through different mechanisms, the initial action of hormones being determined by their membrane effects upon vascular myocytes.