Although the focus of significant investigative interest, the mechanisms involved in basal and gonadotropin-releasing hormone (GnRH)-stimulated luteinizing hormone (LH) release remain to be elucidated. Cyclic AMP has been proposed as an intermediary in signaling the release of LH. There is general agreement, however, that this nucleotide most likely does not elicit the immediate release of LH as is the case with growth hormone and prolactin; rather, the role of cyclic AMP may be to regulate the amount of LH available for release which is, in turn, a function of the prevailing neural and gonadal hormonal milieu. The mechanisms controlling cyclic AMP formation within the gonadotrope as well as those through which the nucleotide exerts its effects, and the question of whether all or only some gonadotropes synthesize and respond to cyclic AMP require definition. Thus, using rat anterior pituitary tissue maintained in several culture systems, a variety of probes which increase intracellular cyclic AMP, and a number of biochemical techniques, I propose to determine: I. Time/concentration relationships for GnRH-stimulated cyclic AMP accumulation. To be addressed specifically are the effects of gender and the hormonal environment of the donor animal on basal and GnRH-stimulated cyclic AMP accumulation. II. The effects of agents which increase intracellular cyclic AMP on cellular and released LH both basally and in response to GnRH. The physico-chemical and biological properties of LH basally and in response to cyclic AMP will be determined by isoelectric focusing and bioassay. In addition, glucosamine incorporation into LH and synthesis of LH will be monitored, the latter via determination of leucine incorporation and measurement of LH messenger RNA. The effects of the gonadal milieu on these processes will be closely scrutinized. III. The effects of agents which enhance intracellular cyclic AMP on basal and GnRH-stimulated LH release by individual gonadotropes. Using the hemolytic plaque assay, the question of whether all or only some cells demonstrate potentiation of LH release after stimulation of cyclic AMP production will be determined as will the effect of gender and the hormonal milieu on the numbers of """"""""responsive"""""""" versus """"""""non-responsive"""""""" cells.
