AIM: To investigate the effects of taurolithocholate (TLC)on the canalicular motility in isolated rat hepatocyte cou-plets (IRHC).METHODS: TLC was added to IRHC at concentrationsof 10 and 50 μmol/L, respectively. In each group, fi vetime-lapse movies containing 3 representative bile cana-liculi were taken under phase-contrast microscopy for12 h. The number of bile canalicular contractions andthe intervals between consecutive canalicular contrac-tions were calculated. Furthermore, the effects of TLC onIRHC were examined by transmission electron micros-copy.RESULTS: The bile canalicular contractions were spon-taneous and forceful in the controls. Active vesicularmovement was observed in the pericanalicular region.Immediately after the addition of TLC, the bile canaliculiwere deformed, and canalicular bile was incorporatedinto the vacuoles. The canaliculi were gradually dilated,and canalicular contractions were markedly inhibited byTLC. The vesicular movements became extremely slowin the pericanalicular region. The number of canalicularcontractions significantly decreased in the TLC-treatedgroups, as compared with that in the controls. The timeintervals were prolonged, as the TLC dosage increased,indicating that bile secretion into the canaliculi wasimpaired with TLC. Transmission electron microscopyrevealed the lamellar transformation of the canalicularmembranes in IRHC treated with TLC.CONCLUSION: TLC impairs both the bile canalicularcontractions and the canalicular bile secretion, possiblyby acting directly on the canalicular membranes in TLC-induced cholestasis. AIM: To investigate the effects of taurolithocholate (TLC) on the canalicular motility in isolated rat hepatocyte cou-plets (IRHC). METHODS: TLC was added to IRHC at concentrations of 10 and 50 μmol / L, respectively. The number of bile canalicular contractions and the intervals between consecutive canalicular contrac-tions were calculated. Furthermore, the effects of TLC on IRHC were examined by transmission electron micros -copy.RESULTS: The bile canalicular contracts were spon-taneous and forceful in the controls. Active vesicularmovement was observed in the pericanalicular region. Immediately after the addition of TLC, the bile canaliculiwere deformed, and canalicular bile was incorporatedinto the vacuoles. The canaliculi were gradually dilated, and canalicular contractions were markedly inhibited by TLC. The vesicular activities became extremely slowin the The number of canalicular events significantly decreased in the TLC-treated groups, as compared with that in the controls. The timeintervals were prolonged, as the TLC dosage increased, indicating that bile secretion into the canaliculi wasimpaired with TLC. Transmission electron microscopy reproduced the lamellar transformation of the canalicular cells in IRHC treated with TLC. CONCLUSION: TLC impairs both the bile canalicularcontractions and the canalicular bile secretion, possiblyby acting directly on the canalicular membranes in TLC-induced cholestasis.