Excretory function in cultured hepatocytes from griseofulvin-treated mice

We determined the role of cytokeratin (CK) intermediate filaments in the excretory function of hepatocytes in cultured hepatocytes containing Mallory bodies (MBs) from the livers of griseofulvin (GF)-fed mice. Hepatocytes for primary culture were obtained from GF-fed and control mice using the 0.1% collagenase perfusion method. Each component of the cytoskeleton in cultured hepatocytes and liver frozen sections was visualized by immunofluorescence. The whole mount extraction of hepatocytes was carried out using 0.5% Triton X-100. To examine the excretory function of the bile canaliculi (BC), fluorescein diacetate and horseradish peroxidase were used as visible excretory products. Thin sections of the cultured cells were made by the "pop-off" method for electron microscopic examination. Frozen sections of livers from the GF-fed mice showed that the MBs were stained with a rat monoclonal antibody to mouse CK, but the CK filaments in the cells containing MBs did not stain. The intercellular BC were reduced in number in the livers of the GF-fed mice compared with the controls. At 3 hours after seeding, hepatocytes with MBs were not stained, but by 24 hours the CK filament network stained normally in cells containing MBs. The loss of staining of the CK filaments was therefore rapidly reversible in the absence of GF in tissue culture. This reversion to normal was prevented by adding 2 x 10(-4) m GF to the culture medium. Thus, the loss of the CK filament antigenic determinants was directly maintained by GF in vitro. The extracted hepatocytes showed spherical canalicular sheaths formed by the CK filaments within the cytoplasm. This was confirmed in "pop-off" sections which revealed that the canaliculi were lined by microvilli and by the localization of actin around the canaliculi as visualized by immunofluorescence. Excretion of fluorescein diacetate into the intracytoplasmic BC was seen both in the cells from GF and control mice but uptake of horseradish peroxidase was markedly reduced by the hepatocytes from the GF-fed mice. The results show that the hepatocytes containing MBs do not form intercellular BC and excretion of fluorescein diacetate into intracytoplasmic BC is not impaired but the uptake of horseradish peroxidase is markedly reduced. The results imply that the rearrangement of the cytoskeleton induced by GF causes both structural and functional deficits in the affected hepatocytes.