Induction of sister chromatid exchange by ethyl carbamate and vinyl carbamate

High levels of sister chromatid exchanges (SCEs) can be induced in murine bone marrow, alveolar macrophages and regenerating liver cells by carcinogenic carbamate esters; however, the frequencies observed in the latter two tissues, which are also common tissues for carbamate-induced tumours, are relatively enhanced compared to the frequency in bone marrow. Relative to these tissues, peripheral blood lymphocytes, which do not divide during in-vivo exposure but which can be cultured in vitro, exhibit considerably lower levels of ethyl-carbamate-induced SCEs. Lymphocytes, however, are uniquely able to accumulate SCE-inducing lesions produced by multiple treatments with ethyl carbamate. In the present study, significantly elevated levels of SCEs were still apparent in lymphocytes of BDF1 mice eight weeks after a series of 12 multiple injections (2.2 mmol/kg; 3 times weekly) of ethyl carbamate. Long-term persistence of genetic damage produced by ethyl carbamate in murine lymphocytes is in agreement with our previous findings of highly persistent SCE-inducing damage in murine bone marrow and alveolar macrophage cells. The highly persistent nature of ethyl-carbamate-induced DNA damage and/or its continued ability to induce SCEs is undoubtedly relevant to its tumourigenic activity.