ALKALINE PHOSPHATASE ACTIVITY IN THE GONADOTROPIC CELLS OF SWINE ADENOHYPOPHYSIS

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In the adenohypophysial cells of swine (S-AHP cells), alkaline phosphatase (ALPase) activity was detected along the plasma membrane and in the cytoplasm. The cells positive for ALPase activity (ALPase cells) were identified as gonadotropic cells by the immunostaining for luteinizing hormone (LH) and follicle-stimulating hormone (FSH). ALPase cells were responsible for the production of both LH and FSH but not for the production of TSH. Ultracytochemically, ALPase cells contained clustered ovoid secretory granules in size ranging from 150 to 400nm. The fine structural organization corresponded to that of swine gonadotropic cells. The product of ALPase activity was localized on the plasma membrane and in the vesicles. The intense activity was detected on the plasma membrane which was engaged in cell to cell contact. In close proximity inside the membrane activity, the endoplasmic reticulum was well developed. The findings suggest that the expression of plasma membrane-associated ALPase may be involved in the interaction between gonadotropic cells.