Ultracytochemical localization of alkaline phosphatase in swine gonadotropic cells

In swine gonadotropic (SGT) cells, the alkaline phosphatase (APase) activity was ultracytochemically demonstrated on the outer surface of the plasma membrane and in some vesicles in the cytoplasm. The plasma membrane-associated APase activity was sporadically detected on the outer surface and was intense at the site adjacent to the next SGT cells or follicular cells. APase-positive vesicles occurred around the Golgi apparatus and in the periphery of SGT cells. Some of the vesicles positive for APase activity attached to the plasma membrane. These results suggest that APase is synthesized in SGT cells and moves to the plasma membrane.