Evidence for membrane-mediated chromosomal damage by aflatoxin B1 in human lymphocytes.

The hepatocarcinogen aflatoxin B1 (AFB1) was found to be a potent clastogen for phytohemagglutinin stimulated human lymphocytes. It also induced sister chromatid exchanges. These types of chromosomal damage were induced at very low levels of covalent AFB1 - DNA adducts suggesting that AFB1 operates in part by indirect action because of its membrane-active character. The membrane-active character of AFB1 is documented by the following results: (i) AFB1 stimulated the excretion of hydroxy- and/or hydroperoxy-arachidonic acid (AA) and free AA into the culture medium; (ii) the phospholipase A2 inhibitor p-bromophenacylbromide was anticlastogenic ; (iii) the inhibitors of the oxidative metabolism of AA indomethacin, flufenamic acid, 5,8,11,14-eicosatetraynoic acid, nordihydroguaiaretic acid and BN 1015 were anticlastogenic . These results are compatible with the induction of DNA damage by indirect action or the formation of covalent adducts via metabolic activation by cooxygenation . The observation that CuZn superoxide dismutase was anticlastogenic indicates the intermediacy of superoxide in DNA damage formation and supports the former mechanism.