Sex difference in pituitary cyclic AMP response to gonadotropin-releasing hormone.

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Abstract
To examine the possible role of pituitary cyclic[c]AMP in the mechanism of luteinizing hormone (LH) release, the effects of gonadotropin-releasing hormone (GnRH) on pituitary cAMP concentration and LH release were studied in male and female rats at different ages. Incubation of pituitaries derived from immature or adult female rats for 20-240 min with GnRH (1-25 nM) resulted in a 6- to 33-fold augmentation of LH release without any increase in pituitary cAMP level. Pituitaries derived from immature males responded to GnRH (1 nM) with an increase in LH release, but no change in cAMP level was observed. Higher concentrations of GnRH (5-25 nM) induced augmented cAMP accumulation in these animals, but this response was demonstrable only after 90 min of incubation; significant stimulation of LH release occurred within 20 min. GnRH failed to stimulate cAMP production in pituitaries from mature male animals castrated 10 days before collection of the glands, although the stimulatory action of GnRH on LH release was not impaired by castration. Testosterone replacement restored the pituitary cAMP response to GnRH stimulation. Incubation of pituitaries derived from immature male or female rats with a cAMP derivative (8-bromoadenosine 3'',5'',-cyclic monophosphate; 1 mM) did not affect LH release; the release of growth hormone was augmented. Because enhanced cAMP production in response to GnRH stimulation occurred only in pituitaries derived from intact adult males, cAMP cannot be regarded as the exclusive mediator of GnRH action on pituitary LH release.

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