Studies on Interactions Between the Ovary and Pituitary Follicle-Stimulating Hormone in the Golden Hamster

Abstract

During the first 3 days of the oestrous cycle of the hamster, pituitary follicle-stimulating hormone (FSH) is relatively constant. However, a decrease in concentration occurred between days 3 and 4. The drop in pituitary FSH\p=m-\whichwas not statistically significant\p=m-\coincided with a period of follicular atresia.After unilateral ovariectomy on day 1, the remaining ovary ovulates twice the normal number of ova. After semi-spaying, pituitary FSH increased over control values on days 2 and 3 and then decreased sharply by day 4. This suggests that the release of FSH between days 3 and 4 prevents atresia and is therefore responsible for compensatory ovulation. Bilateral ovariectomy on day 1 resulted on days 2 and 3 in pituitary FSH concentrations comparable to those in the unilaterally ovariectomized group. However, pituitary FSH increased markedly on day 4 in the bilaterally ovariectomized hamster.Superovulation of approximately 70 eggs occurs after the administration of 60 i.u. pregnant mare serum (PMS) on day 1. A drastic decrease in pituitary FSH took place on days 3 and 4, indicating reduced synthesis of the hormone. The decrease in pituitary FSH between days 2 and 3 is due to ovarian stimulation by PMS inasmuch as the decrease did not occur in animals bilaterally ovariectomized and injected with PMS. The existence of a 'short feedback loop' for FSH is demonstrated by the finding that the increase in pituitary FSH between days 3 and 4 was much greater in bilaterally ovariectomized females than in castrated animals injected with PMS.

Effects of polyethylene IUDs and unilateral ovariectomy in golden hamsters

“…A two-fold increase after unilateral ovariectomy was not observed in the present study because we counted implantation sites rather than the number of ova released (Grady & Greenwald, 1968 ;Joshi & Labhsetwar, 1973). Draper (1965) found nearly complete compensation in the number of implantations in one strain of hamster but her data from the cream strain were similar to those of this study, indicating a possible strain difference.…”

Brain Histamine Levels in the Hamster during the Estrous Cycle and on Selected Days of Pregnancy

“…In the hamster cycle, the corpora lutea from that ovulation develop in the first 2 days of a cycle and begin to degenerate on day 3 [7][8][9]14], In several papers, Greenwald and coworkers have stressed the importance of day 4 during which LH is released from the pituitary to stimulate ovulation [6][7][8][9], Subsequently, the progesterone levels rise in prepara tion for heat. Plasma LH levels are high early on day 4 but fall late in the day and are lowest the next day [17,24].…”

Durational effects of hemispaying on ovarian hypertrophy and estrous cycle in albino rats

“…availability of serum gonadotrophins to the remaining single ovary after hemispaying, since no increase in the pituitary gonadotrophins is observable after hemispaying (McLaren 1963(McLaren , 1966Edgren et al 1965). However, this contention is questioned as there is an increase in the gonadotrophin output, due to decrease in the circulating estrogen after hemispaying which is responsible for the ovarian compensatory hypertrophy (Grady and Greenwald 1968 ;Benson et al 1969;Walshen 1970Walshen , 1972Howland and Skinner 1973). But according to Greenwald (1968) and Peppler (1972) the mechanism of ovarian hypertrophy involves not only an increase in the output of pituitary gonadotrophins, but also the time of exposure to the available gonadotrophins.…”