Suppression of the positive feedback of estradiol benzoate on gonadotropin secretion by an inhibitory analog of luteinizing hormone-releasing hormone (LRH) in oophorectomized rhesus monkeys: evidence for a necessary synergism between LRH and estrogens

The Journal of Clinical Endocrinology and Metabolism
R H AschA V Schally

Abstract

Estrogens have a biphasic effect on gonadotropin (FSH and LH) secretion in human and nonhuman primates. Recent studies suggest that estrogens induce negative as well as positive feedback on gonadotropin secretion by a direct action at the pituitary gland. To further investigate the mechanism by which estrogens modulate gonadotropin secretion, the following experiments were performed. Oophorectomized rhesus monkeys were injected with estradiol benzoate (EB) at a dose of 40 micrograms/kg sc at zero time (controls). Three groups of animals received, additionally, an inhibitory analog of LRH, [Ac-D-p-Cl-Phe1,2, D-Trp3,D-Arg6,D-Ala10]LRH (200 micrograms, sc, daily) at 1) -48 to 48 h, 2) 0-48 h, and 3) 24-48 h from EB treatment, respectively. Blood was collected at -72, -48, -24, and 0 h, every 6 h from 6-84 h, and 96 and 116 h after EB; FSH and LH levels were measured by RIA. Control animals had a 70-80% decrease in baseline FSH and LH levels during the first 24 h after EB injection, followed by a sharp rise to 60-80% above basal levels 42-48 h post-EB. In contrast, animals that received the inhibitory analog of LRH in different regimens had more pronounced and prolonged negative feedback of EB on gonadotropin concentrations. The po...Continue Reading

Citations

Jun 1, 1985·Advances in Contraception : the Official Journal of the Society for the Advancement of Contraception·R H AschA V Schally
Oct 6, 2005·Reproductive Biology and Endocrinology : RB&E·Mohamed F M MitwallyMichael P Diamond
Mar 1, 1987·Gynecological Endocrinology : the Official Journal of the International Society of Gynecological Endocrinology·A L ShadmiJ Blankstein

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