Binding of GnRH to the Pituitary Plasma Membranes, Cyclic AMP, and LH Release
It is well documented that the regulation of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion is a complex phenomenon in which many factors may take part. Among those factors, the hypothalamic peptide gonadotropin-releasing hormone (GnRH) certainly plays, at least in the majority of mammals, a very important role. However, it has been shown that its action at the pituitary level is modulated by various substances such as steroids, neuromediators, and perhaps other neuropep-tides. On the other hand, GnRH also seems to stimulate the synthesis of LH and FSH, and it is possible that there is a relationship between the rate of synthesis of gonadotropins and their rate of release. Consequently, the mechanism of action of GnRH is not a simple molecular process, but rather results from the interaction of GnRH with one or more other factors with different cell components. It would be of great interest to understand the mechanisms of all these interactions at the cellular and molecular levels, but unfortunately no conclusive data are yet available. To simplify the problem, we will not take into consideration the modulating action of different factors on the releasing effect of GnRH, but will rather restrict our topic to two main aspects of the cellular mechanism of action of this neurohormone, i.e., the concept of the receptor of GnRH and the possible involvement of cyclic AMP (cAMP) as an intermediate in the releasing mechanism of LH.
KeywordsLuteinizing Hormone Adenylate Cyclase Pituitary Cell cAMP Accumulation Pituitary Tissue
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