Cytochemical localization of adenylate cyclase activity in the rat anterior pituitary.

The cytochemical localization of adenylate cyclase was studied in relation to the secretory function of the anterior pituitary glands of male rats. The reaction product of adenylate cyclase was localized on the outside of plasma membranes, but was not detected intracellularly. High activity of adenylate cyclase was detected on somatotrophs and microvilli of follicular cells, whereas no activity was found on thyrotrophs or corticotrophs. Although most of the gonadotrophs showed little or no adenylate-cyclase activity, some was detected in a small number of gonadotrophs in the central portion of the gland. In somatotrophs, activity was not detected on the plasma membranes facing perivascular spaces where exocytotic extrusion of secretory granules was frequently observed, although the remaining areas of plasma membranes of the same somatotrophs were associated with high levels of adenylatle-cyclase activity. These findings indicate that the association of a high level of adenylate-cyclase activity is not directly related to the ability of the plasma membranes to fuse with secretory granule membranes.