title: The inhibitory action of oestradiol-17-beta and progesterone on venous smooth muscle.
abstract: 1 The in vitro action of oestradiol-17-beta (0.1, 1.0 and 10.0 mug/ml) and progesterone (0.1, 1.0 and 10.0 mug/ml) on the spontaneous activity of the portal veins in female rats at different stages of gestation was studied. 2 Progesterone caused the spontaneous mechanical activity in the rat portal vein to decrease in amplitude and increase in frequency. This action was dose-dependent and the sensitivity of the tissue decreased throughout pregnancy. 3 Oestradiol-17-beta had a biphasic effect on spontaneous mechanical activity in the rat portal vein. At 0.1 mug/ml the vessel was stimulated while a similar effect to progesterone occurred with higher concentrations. The tissue was more sensitive to oestradiol at 7 days of gestation than at either the 10-14 or 17-21 day periods of gestation. 4 These effects of oestradiol and progesterone were still  seen after blockade of the beta-adrenoceptors. 5 Hydrocortisone (10 mug/ml) had no inhibitory effect on the spontaneous mechanical activity of the vein. 6 The veins from the 17-21 days pregnant animals showed a smaller amplitude of contraction than comparable non-pregnant females.
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D006854:Hydrocortisone / Q000494:pharmacology*; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D011169:Portal Vein / Q000187:drug effects*; D011247:Pregnancy; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D013997:Time Factors
chemical_list: D000319:Adrenergic beta-Antagonists; D011374:Progesterone; D004958:Estradiol; D006854:Hydrocortisone