Localization of Gamma-Glutamyltranspeptidase and Alkaline Phosphatase in Rat Hepatoma Cell Line, McA-RH 7777

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I examined the localization of gamma-glutamyltranspeptidase (GGT) and alkaline phosphatase (ALP) in the rat hepatoma cell line, McA-RH 7777, using enzyme cytochemical and immunocytochemical means. Both enzymes were confined to the cytoplasm around the nuclei. Golgi markers, namely Golgi 58K protein and a substance that reacts to wheat germ agglutinin (WGA), were also localized in the same sites. When McA-RH 7777 cells were cultured in a medium supplemented with dexamethasone, GGT activity was found in the borders between adjacent cells in addition to the cytoplasm around the nuclei. Moreover, the number of microtubular fibers in the cytoplasm increased remarkably. When McA-RH 7777 cells were synchronously cultured with excess thymidine and hydroxyurea, GGT and ALP were localized during the S〜G_2 period in the cell cycle at the borders of adjacent cells and were also found in the cytoplasm around the nuclei. Most McA-RH 7777 cells during this period assumed a flat form with numerous cell to cell contacts. This indicates that contact between adjacent McA-RH 7777 cells promotes the translocation of GGT or ALP from the Golgi apparatus to the plasma membrane.