Gonadotropins in Female Rats Androgenized by Various Treatments: Prolactin as an Index to Hypothalamic Damage

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Abstract
In female rats treated neonatally with 10 µg estradiol ben-zoate (EB), 250 µg androstenediol-propionate, 250 µg dehydroepiandrosterone (DHEA) or various (10, 50, 250, 1,250 µg) doses of testosterone propionate (TP), we compared the age at which vaginal opening occurred, the incidence of persistent estrus, the ovarian, uterine, adrenal, and pituitary weights, and the pituitary and serum gonadotropin (FSH, LH, prolactin) concentrations. Groups of animals were killed for study at 40, 90 and 150 days of age. EB and 50,250 and 1,250 µg TP given at 5 days of age induced precocious vaginal opening. Although none of the animals given DHEA became anovulatory, 99 % of those treated with the other steroids were in constant estrus by 90 days of age. The only indices measured which could be correlated with the andro-genization treatment were pituitary and serum prolactin. The pituitary prolactin content increased with age in all anovulatory females and was higher than that in animals given DHEA. Serum prolactin was linearly related to both the dose of TP given and the age of the animals. The results are consistent with the view that loss of prolactin-inhibiting control mechanisms of the hypothalamus is a consequence of aging. Whether this is related to a loss of neurons or only a loss of function is unknown. Treatment of the neonate with compounds including estrogens and androgens also causes a loss of function of these neurons and, consequently, the prolactin increase with age is accelerated.
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