Studies on vinblastine-induced autophagocytosis in mouse liver. III. A quantitative study.

The microtubule inhibitor vinblastine (25 mg/kg, i.p.) induces autophagocytosis in mouse hepatocytes. The formation of autophagic vacuoles, their contents, and other cellular changes after vinblastine injection in hepatocytes, were studied by light and electron microscopic morphometric analysis. The volume density of autophagic vacuoles increased significantly during the experimental period (24 h). This increase was due to the significant increase in their number, which was approximately 5-fold 4 h, 12 h and 24 h after vinblastine injection. The mean volume of the autophagic vacuoles increased significantly 1 h after vinblastine injection, at which time the formation of new autophagic vacuoles was at its greatest. There was an accumulation of single membrane-limited, obviously older autophagic vacuoles in the cytoplasm. Their volume density was at its maximum 12 h after injection, suggesting a retarded turnover of autophagic vacuoles. The segregation of cytoplasmic components into autophagic vacuoles may not be selective after vinblastine injection. The injurious effects of vinblastine were evident both in light and electron microscopic studies. In the parenchymal cells the Golgi cisternae were dilated and disorganized and the volume density of the Golgi apparatus was significantly decreased 12 h after vinblastine injection. The volume density of lysosomes was increased during the 12 h after vinblastine injection. Vesicles containing very low density lipoprotein particles accumulated in the cytoplasm so that their volume density was significantly increased during the entire experimental period. Vinblastine apparently interfered with the transport and secretion of the very low density lipoproteins from the parenchymal cells.