Action of Adrenocorticotropin on Pregnancy and Litter Size in Rats

¹ From the Department of Anatomy, Yale University School of Medicine, New Haven, Connecticut

Previously it was reported that adrenocorticotropin (ACTH) displayed the ability to restrict the action of estradiol-17ß in uterine growth and of progesterone in decidual development. This study concerns the influence of a highly purified and potent preparation of ACTH on pregnancy and litter size in albino rats of known reproductive vigor. Experimental procedures consisted of injecting ACTH prior to, immediately after mating and 11 days after mating. These data indicate that ACTH has the ability to reduce litter size and produce a large number of stillbirths. The most marked effects were observed when ACTH was injected on the day of mating and for 6 subsequent days. Normally, the litter size of nontreated controls is 9.6 ± 0.5. The daily injection of 2.0 and 4.0 mg ACTH daily for 7 days after mating effected reduced litters, 5.0 ± 1.7 and 3.9 ± 1.5, respectively. Furthermore, such treatment produced 27 stillborns on the 2.0-mg dosage and 39 on the 4.0-mg treatment. ACTH administered to adrenalectomized rats neither modified pregnancy nor litter size. ACTH given to intact rats effected a decrease in the fetal body weights. Such was not observed in the adrenalectomized groups nor in the ACTH-treated, adrenalectomized series. These data strongly indicate that the effects observed are mediated by way of the adrenal glands, and additional evidence is offered supporting the contention that there are numerous interactions among hormones of adrenal cortex and the ovaries.