[The effect of pregna-D'-pentarans on myometrial contractile activity in pregnant rats].

The authors studied the effect of synthetic gestagens on spontaneous contractility of the myometrium in pregnant rats. The direction of the effect of progesterone and its analogs on the contractility is determined by stereochemistry of the linkage of rings A and B of the steroid molecule. Compounds possessing translinkage (5 beta-steroids) increase the amplitude of myometrium contraction, whereas their analogs with cms-coupling of rings A and B (5 alpha-steroids), and 4,5-unsaturated steroids reduce it.