Effect of Luteinizing Hormone and Human Chorionic Gonadotrophin on Corpora Lutea in Rats Bearing Pituitary Autografts

Abstract

Rats bearing pituitary autotransplants received injections of luteinizing hormone (LH) for 9 days or human chorionic gonadotrophin (HCG) for 6 days. Both compounds caused significant increases in ovarian and uterine weights as well as vaginal mucification, observed 1 day after the last injection. Luteal regression and a decrease in uterine weight compared to control animals were observed 35 days after final injection with each compound. Continuous dioestrous vaginal smears were observed in all groups. In hypophysectomized rats, HCG, but not LH, caused an increase in ovarian weight which was statistically significant on the day after the final injection in one of two experiments. Uterine weights were increased after LH and HCG treatments. Vaginal cornification was evident 3\p=n-\4 days after initiation of treatment with either hormone. When ovariectomy preceded hypophysectomy, there was no increase in uterine weight and no vaginal cornification in response to HCG treatment indicating the essential role of the ovaries. The effects in rats bearing auto-transplanted pituitaries as well as in hypophysectomized rats are attributed to the stimulation of oestrogen secretion from the ovaries. It is suggested that the rapid rate of luteal regression in rats bearing transplanted pituitaries is initiated by an increase in metabolic activities due to LH or HCG.

Effect of Human Chorionic Gonadotrophin on the Uterus and Ovaries of Hypophysectomized Rats

“…The present experiments confirm the results previously reported pertaining to the effects of HCG on the ovaries and uteri of hypophysectomized and pituitary autografted rats (Stolzenberg et al 1969). Large amounts of HCG have been reported to induce follicle stimulation in intact immature rats whereas excessive amounts are required in hypophysectomized immature rats (Simpson, 1959).…”

“…The present results and those previously reported (Stolzenberg et al 1969) support the concept that LH has an important role in the luteolytic process of rats (Rothchild, 1965). A number of reports indicate a luteolytic effect by the relatively longterm action of a pituitary gonadotrophin, which appears to be LH (Rothchild, 1965).…”

“…This is followed by regression of the corpora lutea (Stolzenberg et al 1969). In similar studies on hypophysectomized rats, HCG but not LH, caused an initial increase in ovarian weight.…”

“…Experimental animals, surgical procedures and tissue preparation were as described previously (Stolzenberg et al 1969). Unless otherwise stated, hypophysectomies were performed at metoestrus on 10-to 12-week-old rats, which were introduced into an experiment 4-10 days later.…”

“…The administration of bovine luteinizing hormone (LH) or human chorionic gonadotrophin (HCG) to rats bearing pituitary autografts causes an immediate increase in ovarian and uterine weights (Stolzenberg, Eggert, Harrington & Linkenheimer, 1969). This is followed by regression of the corpora lutea (Stolzenberg et al 1969).…”