Hyperprolactinemia decreases the luteinizing hormone-releasing hormone concentration in pituitary portal plasma: A possible role for β-endorphin as a mediator

Dipak K. Sarkar, Samuel S.C. Yen

Research output: Contribution to journalArticle

97 Scopus citations

Abstract

Hyperprolactinemia can reduce the LH secretion in rats, but the mechanism of the effect of PRL is not clear. We have investigated the actions of PRL on the secretion of LHRH and LH and the interaction among PRL, β-endorphin (β-EP), and LHRH. The effects of PRL on LHRH and LH secretion were studied in ovariectomized female rats after transplanting four anterior pituitaries to the right kidney capsule of each ovariectomized rat for 2-3 weeks. The level of PRL in rats with pituitary transplants was approximately 5 times higher than that in control rats. The concentration of LHRH in pituitary portal plasma of hyperprolactinemic rats was approximately 4 times lower than that in control rats. Hyperprolactinemic animals also showed lower plasma LH levels than the controls. Since β-EP inhibits the secretion of LHRH, we have tested whether the reduced secretion of LHRH in hyperprolactinemic ovariectomized rats is associated with an increase in β-EP activity. This was studied by measuring the concentration of β-EP in pituitary portal plasma and the response of LHRH and LH to the opiate antagonist naloxone. The level of β-EP-like immunoreactivity in pituitary portal plasma was significantly higher in hyperprolactinemic rats than in control animals. Naloxone (10 mg/kg, sc) increased both LHRH and LH concentrations in hyperprolactinemic rats, but not in control rats. The present results demonstrate that hyperprolactinemia can reduce LHRH release and suggest a possible involvement of β-EP in the PRL inhibitory action on LHRH.

Original languageEnglish (US)
Pages (from-to)2080-2084
Number of pages5
JournalEndocrinology
Volume116
Issue number5
DOIs
StatePublished - May 1 1985
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Endocrinology

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