2,4,6-TRICHLOROPHENOL (TCP) INDUCES CHROMOSOME BREAKAGE AND ANEUPLOIDY IN-VITRO

2,4,6-Trichlorophenol (2,4,6-TCP), a non-mutagen to Salmonella, was re portedly negative in tests for chromosome breakage in vitro, but did p roduce numerical chromosome changes and micronuclei in V79 cells (Jans son and Jansson, 1992). This apparent specific ability to induce aneup loidy is of interest since aneuploidy testing is not part of routine g enotoxicity test procedures. Here we show 2,4,6-TCP clearly induces st ructural chromosome aberrations in CHO cells and in V79 cells using a 3-h treatment and 20-h sampling time (17-h recovery). The isomers 2,4, 5- and 2,3,6-TCP were also clastogenic in this protocol. There was no increase in aberrations when we used the protocol of Jansson and Janss on (1992), i.e., a 24-h treatment with sampling either immediately, or with a 24-h recovery period. However, positive results were obtained when a recovery time of 4-12 h was allowed after the 24-h treatment wi th 2,4,6-TCP. Previous negative aberration tests of 2,4,6-TCP (Gallowa y et al., 1987; Ishidate, 1988) are also likely due to inappropriate p rotocols. All these results were obtained without S9 metabolic activat ion. We also found positive results in CHO cells when 2,4,6-TCP was te sted with S9. The present study demonstrates that 2,4,6-TCP induces bo th structural and numerical aberrations, and underscores the importanc e of protocol design, in particular the appropriate recovery time afte r treatment, for detecting clastogenic activity in vitro.