Demonstration of vesicular-dependent bile flow in the sucrose-loaded rat

The contribution of the hepatocyte vacuolar apparatus to bile fluid formation was assessed by studying the transcellular transport and biliary excretion of the fluid-phase marker sucrose. In rats sucrose-loaded by IP administration of sucrose, electron microscopy showed expansion of the vacuolar apparatus and numerous large lysosomelike structures in hepatocytes. Subcellular distribution studies showed that sucrose was sequestered in lysosomes. Compared with controls, sucrose-loaded rats had a 30% higher (P less than 0.01) bile flow with no change in biliary bile acid or electrolyte concentrations. Administration of colchicine ablated the sucrose-induced choleresis and resulted in parallel changes in biliary secretions of sucrose and lysosomal enzymes. Our data suggest that in the sucrose-loaded rat, the hepatocyte vacuolar apparatus may contribute significantly to bile formation by microtubule-dependent release of fluid into bile by exocytosis.