EFFECT OF HYPOXIA ON THE FREQUENCY OF BLEOMYCIN-INDUCED MICRONUCLEI

Normal G(0) pig lymphocytes were maintained in a hypoxic or aerobic en vironment for one hour and then concurrently exposed to bleomycin at v arying concentrations for a second hour. The cytochalasin-block micron ucleus assay was used to determine cytotoxicity. Exposure to transient hypoxia significantly decreased the frequency of bleomycin-induced mi cronuclei per cell as compared to that observed in oxygenated cells. F urthermore, the frequency of micronuclei per hypoxic cell did not corr espond to any increase in bleomycin dose as observed in oxygenated cel ls. These data demonstrate the significance of transient hypoxia in th e resistance of G(0) cells to the cytotoxic effects of bleomycin and m ay explain the observed selectivity of tumor tissue response to bleomy cin.