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Keywords:

  • actin;
  • bile canaliculus;
  • calcium;
  • calmodulin;
  • cholestasis;
  • cytoskeleton;
  • ML-9;
  • myosin light chain kinase;
  • myosin

ABSTRACT— Active dynamic contraction of bile canaliculi has been observed in cultured doublet hepatocytes using time-lapse cinephotomicrography. This contractile movement plays an important role in normal bile formation. The mechanism of bile canalicular contraction has been proved to involve the Ca2+-calmodulin system and pericanalicular actin filaments. However, the role of myosin in this system is still unknown. In this study, using the newly synthesized myosin light-chain kinase inhibitor ML-9, we found that the treatment of cultured doublet hepatocytes with ML-9 inhibited canalicular contraction. This inhibitory effect suggests that myosin is involved in this complex cellular function and that the integrity of the actin-myosin system, as well as the Ca2a-calmodulin system is essential for normal bile canalicular contraction.