Abstract
Summary
Serum prolactin concentrations in constant-estrus rats sterilized by a single injection of testosterone proprionate on the third day of life and in adult female rats, spontaneously constant-estrus, were compared to levels in adult normal cyclic female rats. Prolactin levels were much greater in androgen-sterilized females (235 ±18 ng/ml) and in spontaneously constant-estrus females (165 ± 17 ng/ml) than in normal cyclic estrus rats (30± 7 ng/ml). In order to demonstrate the role of en-dogenously produced ovarian estrogen in maintaining the high levels of prolactin, ovariectomy was performed on both groups of constant-estrus animals. Bilateral ovariectomy for one and three weeks resulted in a marked decrease in prolactin levels in both experimental groups. These results show that prolactin levels are elevated in androgen-sterilized and spontaneously constant-estrus rats and that the continuous release of estrogen observed in these animals is acting on the hypothalamic-pituitary axis to promote prolactin release.
The authors acknowledge the expert technical assistance of Ms. Josephine A. Morris, Ms. Lucinda Johnson and Ms. Carolyn R. Duszynski.
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