Effects of phalloidin and cytochalasin B on cytoskeletal structures in cultured rat hepatocytes.

In short-term cultures of rat hepatocytes, bile canaliculi enclosed between unseparated cell couplets are able to perform periodical contractions resulting in expulsion of bile. Pericanalicular cytoskeletal proteins are involved in canalicular contractility: F-actin, myosin and tropomyosin are associated around bile canaliculi, as revealed by staining with tetramethylrhodaminyl-phalloidin and by immunofluorescence. Bile canalicular contractility is distributed by cholestatic agents that are known to interfere with actin polymerization; e.g., phalloidin and also cytochalasin B inhibit canalicular contractility and cause pericanalicular vacuolization and formation of blebs. Whereas the association of the cytoskeletal proteins is not affected by treatment with cytochalasin B, treatment with phalloidin results in dissociation of F-actin and myosin, indicating that binding of phalloidin to F-actin impairs its molecular interaction with myosin.