Acute phalloidin toxicity in living hepatocytes. Evidence for a possible disturbance in membrane flow and for multiple functions for actin in the liver cell.

Actin filament based cell functions were examined in freshly isolated hepatocytes using phalloidin as an inhibitor. In particular, cell motility events, namely, surface bleb formation and canalicular contractile movements, were assessed and compared with morphologic changes in the cells. Phalloidin (in 0.1, 1.0, and 10.0 micrograms/ml dosages) was added to the culture medium 4 hours after isolation of the hepatocytes. Cell motility was recorded with time-lapse cinephotomicrography, and the morphologic changes were evaluated by phase-contrast optics and by transmission electron microscopy of serial sections. Membrane-bound pericanalicular cytoplasmic vacuoles appeared first, followed by cytoplasmic protrusions at the cell surface. Vacuolar membrane continuities with the canalicular membrane were noted, and later, with other regions of the cell surface, such that large tortuous irregular membrane-bound canals are seen on serial sectioning to link extracellular and canalicular spaces. These findings suggest a possible disturbance in membrane flow. Canalicular motility was greatly reduced and was dose-dependent. The time-based difference in the changes at the canalicular and sinusoidal surfaces may be indicative of different functions and/or sensitivities of the actin filaments within the liver cell.