Localization of Gamma-Glutamyltranspeptidase and Alkaline Phosphatase in Primary Cultures of Fetal Rat Hepatocytes.

Abstract

The localization of gamma-glutamyltranspeptidase (GGT) and alkaline phosphatase (ALP) in primary cultures of fetal rat hepatocytes was investigated using enzyme cytochemical and immunocytochemical techniques. When hepatocytes were cultured in a medium supplemented with dexamethasone (DEX) or dimethylsulfoxide (DMSO), both enzymes were observed in the plasma membranes along the intercellular spaces that developed between adjacent hepatocytes. On the other hand, in hepatocytes cultured in the basic medium or in medium supplemented with transforming growth factor-β (TGF-β), the enzymes were found in the limited area of the cytoplasm surrounding the nuclei. Connexin-32, a subunit of proteins that comprise gap junctions, was detected along the cell borders in hepatocytes cultured in DEX or DMSO-supplemented medium, but was not found in hepatocytes cultured in the basic medium or in medium supplemented with TGF-β. However, the DEX and DMSO supplements did not cause any changes in the distribution of microtubules in hepatocytes, and numerous microtubular fibers were observed to extend in a radial pattern from the nuclei to the periphery of the cytoplasm in all hepatocytes, irrespective of medium type. These results indicate that assessment of the location of GGT and ALP may help determine the level of hepatocyte differentiation in cultured rat hepatocytes and that intracellular factors other than microtubules are involved in the transport of these enzymes from the cytoplasm to the plasma membrane.