EFFECT OF PROSTAGLANDIN F2 ON SERUM PROLACTIN AND LH CONCENTRATIONS IN MALE AND FEMALE RATS

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Abstract
Virgin male and female rats weighing between 200-250 g were used. Females were ovariectomized 1-2 mo. before use and the effects of prostaglandin F2.alpha. (PGF2.alpha.) were tested before estrogen treatment was initiated. Estradiol benzoate (1 or 10 .mu.g) was injected s.c. 24 h before PGF2.alpha. administration. The tromethamine salt of PGF2.alpha. was injected into the jugular vein at 17.00 h at dose levels of 1, 2.5, 5, 10 or 50 .mu.g/100 g body weight. Control rats were injected with normal saline. Prolactin levels in male rats rose from 27.9 .+-. 2.0 (S.E.) ng/ml in animals given saline to 67.8 .+-. 7.7 ng/ml (P < 0.001) and 49.9 .+-. 8.7 ng/ml (P < 0.02) after treatment with 5 and 10 g PGF2.alpha. respectively. A significant increase in serum prolactin was found in the proestrous rats in response to all the doses of PGF2.alpha. except for the 1 .mu.g dose. Only the 10 .mu.g dose of PGF2.alpha. caused a significant increase in rats in estrus or diestrus I; no change in prolactin values was found in rats treated during diestrus II. Significant rise in prolactin levels occurred only in ovariectomized rats primed with 10 .mu.g estradiol benzoate 24 h before a dose of 10 .mu.g PGF2.alpha.. Serum luteinizing hormone (LH) concentrations in males and females were not significantly affected by PGF2.alpha. treatment. PGF2.alpha. may influence pituitary prolactin release without altering LH secretion. The site of action and physiological role in PGF2.alpha. in the regulation of prolactin release are uncertain. It is probable that PGF2.alpha. may act at the hypothalamic level, since prostaglandins are present in most parts of the brain, including the hypothalamus. Prostaglandins may play an important role in modifying or modulating the actions of other transmitters in the brain.

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