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McNtcp.24 cells are rat hepatoma cells that were made competent to take up conjugated bile acids actively from the culture medium. Treatment of McNtcp.24 cells with certain species of bile acids caused significant changes in cell structure. Incubation of McNtcp.24 cells in medium containing 100 microM taurocholic acid induced a profound alteration of cellular morphology. Very larger vesicles, visible by phase contrast microscopy, were the most prominent feature of bile acid-treated McNtcp.24 cells. Staining of cells with Oil red O and filipin indicated that the vesicles did not contain neutral lipids or free cholesterol. The vesicles remained in the cells after efflux of radiolabeled taurocholic acid from bile acid loaded cells, indicating that these structures are not intracellular stores of bile acids. Electron microscopic analysis of bile acid-treated McNtcp.24 cells confirmed that the vesicles were localized within the cells. Taurine-conjugated bile acid species were generally potent inducers of the morphological changes, although tauroursodeoxycholic acid did not have a significant effect. Unconjugated bile acid species were ineffective or only mildly effective. Bile acid treatment also caused profound alteration of mitochondrial structure. Surprisingly, there was no significant effect on the ability of treated cells to oxidize fatty acids. The bile acid-treated cells remained viable and upon withdrawal of bile acids from the culture medium, the cells returned to normal morphology by 24 h. The morphological changes observed after treatment of McNtcp.24 with bile acids are reminiscent of the morphological changes observed in hepatocytes following induction of cholestasis. |
