The Effect of Progesterone and Oestradiol-17B on the Spontaneous Activity of Isolated Venous Smooth Muscle
Longitudinal strips of bovine mesenteric vein were set up in organ baths and when perfused with a modified Ringer’ s solution showed vigorous irregular spontaneous activity, each contraction lasting about 2 minutes. Experimental strips were exposed to oestradiol-17B and progesterone dissolved in ethylene glycol in doses ranging from 0.5 to 10 /ug/ml and control strips were simultaneously exposed to the vehicle alone. Both hormones depressed the mean tone and the amplitude of the contractions of the experimental strips. Though the changes with the 0.5 /ug/ml doses were small, 10 /ug/ml of either hormone caused a 50% reduction in resting venous tone and almost complete suppression of spontaneous activity. It is concluded that oestradiol-17B and progesterone are venodilator substances in vitro.