EFFECTS OF ACTIVE AND PASSIVE IMMUNIZATION WITH LH-RH ON GONADOTROPHIN SECRETION AND REPRODUCTIVE FUNCTION IN FEMALE RATS

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Abstract
To study the physiological role of LH-RH [luteinizing hormone-releasing hormone] in the regulation of tonic and phasic secretion of gonadotropins, and the existence of FSH-RF [follicle-stimulating hormone-releasing factor] distinct from LH-RH, the neutralization of endogenous LH-RH by passive and active immunization with LH-RH in female rats was attempted. Anti-LH-RH serum prevented pre-ovulatory gonadotropin surges at pro-estrus and ovulation, and it suppressed gonadotropin increase induced by estradiol benzoate or progesterone in ovariectomized rats. Elevated serum gonadotropin concentrations in long-term ovariectomized rats were lowered by anti-LH-RH serum injection. The decrease in FSH [follicle-stimulating hormone] levels was lesser than that in LH [luteinizing hormone] levels. Serum FSH rose without significant changes in serum LH level for 6 h after ovariectomy on pro-estrus or diestrus. The post-ovariectomy rise of FSH was not suppressed by the anti-LH-RH serum which was enough to inhibit serum LH to undetectable levels. Active immunization with LH-RH resulted in decreasing LH levels but failed to alter FSH levels in both the serum and pituitary. Of 10 rats immunized with LH-RH, 7 became constantly diestrous. The weights of anterior pituitary, ovary and uterus of the LH-RH immunized rats were significantly smaller than those of BSA [bovine serum albumin] immunized controls. Ovaries of LH-RH immunized rats contained few fresh corpora lutea. LH-RH evidently plays a significant role in the control of both phasic and tonic secretion of LH and FSH. The existence of FSH-RF distinct from LH-RH or a mechanism which specially controls the basal FSH secretion is indicated.

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