Organ weight changes and pituitary LH content during pregnancy and the early postpartum period in the hamster.

Abstract

Measurements of pituitary LH content, uterine wet and dry weights, ovarian, and pituitary and adrenal weights were obtained for every day of pregnancy subsequent to the postestrous discharge in the hamster and for the first 5 days postpartum in lactating and nonlactating females. Comparisons are made with comparable data previously reported for the estrous cycle and pseudopregnancy. Ovarian and adrenal weights are significantly interrelated in pregnancy. Weights of both drop prior to and after parturition, remaining elevated above pseudopregnant and cyclic values in the lactating females, dropping more sharply in nonlactating females where ovarian weights approach cyclic values as ovulation recurs, usually on the 4th day after parturition. Pituitary weights do not change significantly in pregnancy but do increase significantly above those of the cycle or pseudopregnancy. Pituitary LH content rises until day 11-12, attaining a level at least twice that found in pseudopregnancy. Pituitary LH content remains at a high level in nonlactating females, dropping only with recurrence of ovulation on postpartum 4. In lactating females no ovulation occurs, although the pituitary LH content drops to a level similar to postovulation values by 48 hours postpartum. During pregnancy, uterine dry and wet weights rise and growth is linear; percent of solids drops markedly in late gestation, which, however, is due to the conceptual mass; no such change is obvious in the uterus itself as shown by observations on uteri from which the conceptuses had been stripped. No conclusive evidence was found of a latent cycle during pregnancy, but suggestive points are discussed.