Blastogenic and cytotoxic effects of hexavalent chromium were evaluated by direct, 2 and 20 min oxidation of lymphocytes by 10.0 to 0.0005 mM CrO3 at 0°C. Oxidized cells exhibited concentration-dependent cytotoxicity and the inhibition of tritiated thymidine incorporation rates. When lymphocytes were oxidized first by 1.0 mM periodic acid (H5IO6) and thereafter by 1.0 mM CrO3, the viability and [3H]-TdR incorporation rates of sequentially oxidized cells were identical to the corresponding indicators of lymphocytes oxidized only by CrO3. The reversal of the oxidation sequence restored [3H]-TdR incorporation to control levels and increased cell survival. It is therefore concluded that direct interaction of hexavalent CrO3 with plasma membrane of lymphocytes results in concentration-dependent cytotoxicity and the inhibition of [3H]-TdR incorporation, but it does not induce blastogenesis.

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