COMPARISON OF RESULTS FROM MOUSE BONE-MARROW CHROMOSOME ABERRATION AND MICRONUCLEUS TESTS

Tests for the induction of chromosomal aberrations (ABS) and micronucl ei (MN) in bone marrow cells of mice have been conducted on 65 chemica ls. Although these tests were not conducted with the purpose of-compar ing the outcomes of these two in vivo genetic toxicity endpoints, the availability of these test results permits such a comparison. Based on studies to date, results from the 2 tests agree for more than 80% of the chemicals; 17 gave positive results in both tests, and 36 gave neg ative results in both. Seven chemicals were positive only for ABS and 5 were positive only for MN. Three chemicals that were originally conc luded to be positive for ABS but not for MN were found to induce MN wh en the MN protocol was modified to more closely reflect the ABS protoc ol. Among the 12 chemicals for which there are discrepant results, the re are only 2 for which the difference is convincing. One of these, se lenium sulfide (MN negative, ABS positive) remains an enigma; further studies are being conducted. The second, isoprene (MN positive, ABS ne gative) will be difficult to pursue because the studies reported here were done by inhalation exposure. Based on the outcomes of these compa risons, protocol factors, rather than endpoint specificity, appear to be the major source of discrepant test results. Thus, these results do not support a recommendation that both tests be conducted in a primar y testing scheme for genetic toxicity. (C) 1995 Wiley-Liss, Inc.*