[Effect of synthetic ACTH (beta 1-23 corticotropin) on gestation and parturition in rats]

Daily administration of synthetic ACTH (betaI-23 corticotrophine) from day 15 of pregnancy induces delay or inhibition of parturition in normal or ovariectomized Rats injected or not with estradiol. Parturition takes place at approximatively normal time, when ACTH is stopped and estradiol continued. Radio-immunological assays show an increase of blood progesterone level after ACTH administration in castrated, but not in castrated and adrenalectomized Rats. Mechanisms of ACTH action are discussed.