| Abstract: | The pathogenesis of lithocholic acid (LCA-Na)-induced cholestasis involves a rapid accumulation of cholesterol in the bile canalicular membrane. Since microtubules play an important role in the intracellular transport of many materials, including cholesterol, the present study was undertaken to assess the extent to which they participate in the development of LCA-Na-induced cholestasis. Rats were pretreated with either colchicine (0.2 mumol/100 g body wt.) or saline solution 90 min before injection with LCA-Na (12 mumol/100 g body wt.). Colchicine, although not increasing bile flow by itself, significantly reduced the cholestasis caused by LCA-Na (57-32% reduction in bile flow) without affecting its metabolism into less toxic bile acids or its distribution in blood, liver or bile. Bile canalicular membranes isolated from animals treated with a combination of colchicine and LCA-Na contained less cholesterol than those treated with LCA-Na alone. However, membranes obtained from rats treated with colchicine alone contained much less cholesterol than did controls. It was found that the total amount of cholesterol accumulated within the bile canalicular membrane following LCA-Na treatment (LCA-Na + colchicine versus colchicine alone compared with LCA-Na versus controls) was unchanged by colchicine treatment. In view of these findings it is suggested that the total amount of cholesterol present within the bile canalicular membrane determines the extent of LCA-Na-induced cholestasis, LCA-Na probably moves cholesterol to the bile canalicular membrane via a microtubule independent pathway, and microtubules are unlikely to function in the transcellular transport of LCA-Na. |
