Study on the intracellular mechanism of LH release in the anterior pituitary

Abstract

To study the mechanism of action of luteinizing hormone-releasing factor (LH-RF or Gn-RF) on the rat anterior pituitary in vitro, cyclic-3′,5′ adenosine monophosphate (cyclic AMP), LH, and FSH in tissue and culture medium have been analyzed by radioimmunoassay. Synthetic Gn-RF and rat hypothalamic extract (NIAMD-Rat HE-RP-1) significantly increased cyclic AMP formation in the pituitary within 5 minutes. Less than 5 ng. of Gn-RF induced maximum effect for cyclic AMP formation. Adenyl cyclase activity of pituitary homogenate was also increased by Gn-RF and the HE. Significant increases in the release of LH and FSH were observed after 4 hours' incubation with N6, O2′-dibutyryl cyclic AMP (10 mM.) and theophylline (1 mM.). Synthetic Gn-RF also induced a marked release of both LH and FSH in the medium and increase of LH content in the anterior pituitary. These data support the hypothesis that LH and FSH release by the hypothalamic-releasing factor is mediated by the adenyl cyclase-cyclic AMP pathway.