No abstract

No abstract

Pregnant mice were hypophysectomized on day 6 and injected subcutaneously with various hormones from days 6 to 9 to establish the minimal requirements for the maintenance of functional corpora lutea. Luteal activity was assessed by the maintenance of pregnancy, weight of embryonic swellings, mean diameter and morphology of corpora lutea, and vaginal histology.Treatment with 2 mg progesterone maintained pregnancy but not corpora lutea in three of five animals. However, the embryonic swellings were significantly (P < 0.0005) smaller than those of pregnant control animals. Pregnancy was maintained in all animals when progesterone was combined with 1 qg of estrone. The weights of embryonic swellings and the degree of vaginal mucification in the combined steroid group were similar to those of intact control animals. Treatment with either ovine prolactin, bovine LH, ovine FSH or estrone failed to maintain corpora lutea or pregnancy. Combined injection of prolactin with LH or estrone did not maintain pregnancy or corpora lutea. On the other hand, treatment with 500 pg of prolactin and 200 pg of FSH maintained pregnancy in 12 of 14 animals. All of the aforementioned parameters of luteal activity were comparable to values in intact, control animals.The data indicate that luteal function in the mouse during the early post-implantation period requires a luteotropic complex rather than a single hormone. Prolactin and FSH constitute the minimal luteotropic complex in the pregnant mouse. The luteotropic activity of FSH was not due to its contamination with LH and the effect of FSH was apparently not mediated through estrogen secretion, since pregnancy was not maintained by prolactin and estrone.The maintenance of luteal function in several species apparently requires a hormonal complex rather than a single hormone acting alone (Greenwald and Rothchild, '68). In the hamster, prolactin and FSH serve as a luteotropic complex (Greenwald, '67; Choudary and Greenwald, '67). The precise hormonal requirements in other species have not been determined. Dresel ('35) reported that the administration of exogenous prolactin to cyclic mice prolonged the length of the cycle. Single or multiple ectopic pituitary grafts also produce pseudopregnancy in intact cyclic mice (Browning and White, '63; Hagen and Rawlinson, '63; Dominic, '66), and deciduomata can be induced in such animals by traumatization of the uterus (Dominic, '66). These reports suggest that the ectopic pituitary causes functional maintenance of corpora lutea in mice by secreting prolactin. However, a recent investigation by Jaitly, Robson, Sullivan and Wilson ('65) indicates that prolactin alone is inadequate for the functional mainten-ANAT. Ruc., 163: 373-388.ance of corpora lutea in hypophysectomized pregnant mice. Apparently, in mice bearing pituitary grafts their own pituitary glands are partly responsible for the maintenance of luteal activity. In cyclic hamsters with pituitary transplants the corpora lutea are activated by the joint action of prolactin from the ...

Various parameters of ovarian activity were determined for the intact or hypophysectomized pregnant mouse, as a baseline to establish the nature of luteotropic hormones in this species.Seventeen per cent of White Swiss mice with a vaginal plug were not pregnant at subsequent stages of gestation. The greatest number of failures occurred between days 12 and 15 of pregnancy, coinciding with the temporary absence of antral follicles and regressive changes in the vaginal epithelium. This suggests that there is a period of transient hormonal imbalance before full placental function is established, which is responsible at this time for the peak in embryonic mortality.Two periods of luteal growth were apparent between days 1 and 4 and 10 to 14 of pregnancy. The first histologic evidence of luteal regression occurred at day 16, correlating with renewed squamous cell proliferation of the vaginal mucosa.There were no significant differences in the number of ova shed on day 1 of pregnancy (11.0 f 0.5 ova) and the subsequent number of embryonic swellings at any stage. Gestation in intact pregnant mice lasted 18 days (n = 2) or 19 days (n = 36).The number of young counted late on day 1 post partum (9.1 & 0.5) was significantly less than the number of embryonic swellings as a result of maternal cannibalism.Hypophysectomy on day 1 of pregnancy led to rapid histologic degeneration of the corpus luteum. In this feature, the mouse resembled the hamster rather than the rat. Day 10 of pregnancy represented the earliest time at which, at least in some animals the pituitary could be removed and pregnancy continue. Following hypophysectomy from day 11 on, luteal activity, continuation of pregnancy, fetal and placental weight and vaginal histology were comparable to intact, pregnant mice. This is similar to the hypophysectomized rat in the latter half of pregnancy but differs from the situation in the hamster.On the basis of the present findings and results jn the folbwing paper, it appears likely that the mouse placenta, in addition to secreting a prolactin-like hormone, also produces other gonadotropins.

No abstract