Distribution and dynamics of cell surface-associated cellCAM 105 in cultured rat hepatocytes

The cellular location of cellCAM 105 was studied by indirect immunofluorescence microscopy of primary rat hepatocytes grown in monolayer culture. Staining corresponding to cellCAM 105 was seen both in cell-cell contact areas and on the upper surfaces of the cells. In the cell-cell contact areas the antigen was not accessible to the antibodies unless the cells were either permeabilized with detergent or incubated in a calcium-free medium. Removal of calcium from the medium caused the cells to separate from each other. Within a few minutes wide intercellular clefts were formed, and upon further incubation the cells became stellate-shaped and finally remained in contact with each other only via thin cellular processes. These processes were cellCAM 105-positive and at sites where they attached to the bodies of the contracted cells a granular fluorescence pattern appeared. After 24-48 h of culture, intercellular channels resembling bile canaliculi were sometimes formed in the hepatocyte monolayers. The membranes of these intercellular channels were stained for cellCAM 105. After culture for several days the hepatocytes lost their polygonal shape and gradually acquired a more fibroblast-like morphology. This morphological change was accompanied by a decrease in cellCAM 105-specific fluorescence, both in the cell-cell contact areas and on the free cell surfaces.