Background and Aims: Ethanol is known to alter vesicle-mediated protein trafficking in hepatocytes by undefined mechanisms. In this study, the effects of long- and short-term ethanol exposure on vesicle movements were measured in isolated hepatocytes, and alterations in the function of the microtubule-associated motor enzymes dynamin, kinesin, and dynein, which are believed to support the transport and/or budding of vesicles along microtubules, were tested. Methods: Vesicular movements in isolated hepatocytes exposed to short- and long-term ethanol treatment were measured. Motor adenosine triphosphatase activities and their association with specific membrane organelles were assessed in response to long-term administration of ethanol in vivo or acetaldehyde in vitro. Results: Hepatocytes exposed to short- or long-term ethanol treatment showed a significant reduction in the number of motile vesicles. No alterations in the levels of motor messenger RNA, protein, or enzymatic activity were observed. Interestingly, ethanol had no effect on the association of dynein and kinesin with membranes, whereas there was a significant increase in the amount of dynamin associated specifically with Golgi membranes. Conclusions: Long- and short-term ethanol exposure markedly reduces hepatocellular vesicle transport by a mechanism apparently independent of any alteration in the enzymatic activity of molecular motors, possibly involving a change in the function of dynamin.
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