A Enzyme Cytochemical Study of Intra-Cellular Singnaling System of Anterior Pituitary Hormone Producing Cells.

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It is well understood that extracellular stimuli produce specific responses in the cells by changing the intracellular concentrations of cyclic-AMP and that adenylate cyclase is the enzyme which gives rise to it. Cyclic-AMP in the cell is degraded by cyclic 3',5'-nucleotide phosphodiesterase into adenosine monophosphate, then adenosine monophosphate receives a break-down by 5'-nucleotidase into adenosine and orthophosphate, and terminally results in a cAMP metabolic cascade. Although the cytochemical localization of these enzymes have been studied in many organs, almost no report has appeared on the pituitary gland. The present study aimed at knowing localization of these enzymes in the rat anterior pituitary gland by means of electron microscopic enzyme histochemistry, introducing the following media of Saito and Keino (1975) for adenylate cyclase, Takizawa and Saito (1992) for phosphodiesterase, and Wachstein and Meisel (1975) for 5'-nucleotidase.The reaction product for adenylate cy … More clase activity was observed on the plasma membrane of GH cells. Strongly positive reaction product was observed on the microvilli of some folliculo-stellate cells (F-S cells). The phosphodiesterase activity was demonstrated as positive in the cytoplasm of the PRL cells. In some GH cells, reaction product was weakly observed in the cytoplasm. The reaction products for 5'-nucleotidase were observed positive on the plasma membrane of some of the LH/FSH cells in addition to the GH cells. The above results interestingly suggest that the anterior pituitary cells present specific differences in the cyclic nucleotide metabolizing enzymes in constituent cells. In addition to the anterior pituitary hormone producing cells, ultracytochemical localization of adenylate cyclase and guanylate cyclase was studied in the marginal cell layer surfacing the pituitary cavity. The cells in the marginal cell layer showed strong activity of adenylate cyclase and guanylate cyclase on the plasm membrane facing to the cavity, including micrivilli and cilia. Similar localization of guanylate cyclase activity was observed. The results suggest that the constituent cells of the marginal cell layer may have some regulatory function on the pituitary gland. Less