Prolactin is best known for its effects on the breast, promoting mammary growth and lactation. In some species, including rat, mouse, hamster, sheep and rabbit, prolactin is necessary for the maintenance of the corpus luteum 1-5. Further, a relationship has been recognised between hyperprolactinaemia and ovulatory failure in the human. The site of action is thought to be the hypothalamus and or adenohypophysis6. McNatty et al.7 have postulated a direct ovarian effect of prolactin, reporting that low prolactin levels were essential for progesterone production by preovulatory human granulosa cells cultured in vitro. However, high levels of prolactin decreased progesterone production. The present investigation sought to determine the effect of prolactin on ovulation using the in vitro perfused rabbit ovary preparation. We report that its effects are inhibitory.
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