DNA damage induced by the drinking water mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2[5H]-furanone (MX) in mammalian cells in vitro and in mice

3-Chloro-4-(dichloromethyl)-5-hydroxy-2[5H]-furanone (MX) formed during chl orination of water containing natural organic substances, is a very potent bacterial mutagen. Recently, tumours at multiple sites were reported in rat s given MX-containing drinking water. We have investigated the genotoxicity of MX in mammalian cells exposed in vitro and in vivo using alkaline filte r elution to detect DNA single-strand breaks and/or alkali-labile sites (SS Bs). Concentrations as high as 100 and 300 mu M MX were required to induce detectable levels of SSBs in the HL-60 cells. If MX treatment was carried o ut in the presence of DNA repair inhibitors (AraC plus hydroxyurea), the se nsitivity of the assay to detect MX-induced SSBs was increased by a factor of 100. The presence of serum proteins during exposure resulted in a minor reduction of the MX-induced DNA damage in HL-60 cells at the lowest MX conc entrations. In primary cultures of testicular cells as well as in resting h uman peripheral blood mononuclear cells (PBMC), a slightly increased level of SSBs was observed at MX-concentrations above 30 mu M, this effect was no t further increased by repair inhibitors. In LLC-PK1 renal proximal tubular epithelial cells and in growth stimulated human peripheral PBMC, increased SSBs were detected at MX concentrations as low as low as 3-10 mu M and hig her using repair inhibitors, and at 10 times higher concentrations without repair inhibitors. No dose dependent DNA damage was detected in the liver, kidney, spleen and colon of male B6C3F1 mice administrated high doses of MX (40 and 80 mg kg(-1)). Moderately increased and dose dependent SSBs were d etected in the liver and kidney in the presence of DNA repair inhibitors du ring MX treatment, but no such increase was observed in the spleen and colo n. (C) 1999 Elsevier Science B.V. All rights reserved.