Effects of Adrenocorticotropin on Pregnancy and Prolactin in Mice*

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Abstract
The effect of chronic ACTH administration on pregnancy and serum PRL levels was studied in 40 adrenalectomized and 71 intact house mice. Three periods of gestation were examined: days 1–8 (series I), day 8 to parturition (series II), and day 1 to parturition (series III). Day 1 of gestation was determined by the presence of a vaginal plug. Mice received daily sc injections of 4 U of ACTH or the gelatin vehicle between 0900–1100 h. Bilateral adrenalectomy was performed 7 days before mating, and adrenalectomized mice were maintained on 50 μg cortisone acetate/day. In series I, ACTH treatment reduced maternal body weight, uterine weight, and nidation sites in intact (P < 0.01) and adrenalectomized mice (P < 0.05) compared to their respective controls. In series II, ACTH treatment reduced maternal body weight, uterine weight, litter size and pup size in intact mice (P < 0.01). No significant differences were observed among adrenalectomized ACTH-treated mice and adrenalectomized controls in this series. In series III, ACTH treatment reduced maternal body weight, uterine weight, litter size, and pup size in intact mice (P < 0.05), while in adrenalectomized mice ovarian weight and pup size were decreased and maternal body weight was increased (P < 0.05). Serum PRL values were elevated (P < 0.05) in ACTH-treated intact and adrenalectomized mice compared to levels in their respective controls for all three series. These findings indicate that chronic ACTH treatment in pregnant mice induced hyperprolactinemia which may be significant in impairing reproductive function and the regulation of mammalian population size.