Changes in ultrastructure and function of hypoxic V79 fibroblast cells after treatment with misonidazole.

Morphologic and enzymatic changes due to exposure to the radiosensitizing chemical, misonidazole, have been identified in V79 cells grown in a system in which oxygen tensions and culture density have been controlled. Misonidazole prevented the increase in mitochondrial size normally seen during exposure of these cells to conditions of moderate hypoxia (2 X 10(3) ppm O2). Mitochondrial size was also significantly decreased in cells from exponential cultures exposed to 1 mmol/l misonidazole. Morphologic changes to the mitochondria that varied from data reported elsewhere were also noted. Misonidazole caused a significant initial decrease in cytochrome oxidase activity after 4 hours of exposure of aerobic and moderately hypoxic cultures that did not return to normal in chronically hypoxic cells during continued exposure to the drug.