In vitro cytotoxicity of glycol ethers and oxidation products in CHO cells

The cytotoxicity of several glycol ethers and of some of their oxidation products, the corresponding alkoxy acetates, was compared in Chinese hamster ovary (CHO-K1) cells without metabolic activation. Cytotoxicity was measured in terms of cloning formation ability, and EC50 values (concentrations allowing 50% of the seeded cells to form colonies) were estimated. The results, in the case of unmetabolized glycol ethers tested, showed an increase in toxicity with increasing chain length. The cytotoxicity of the corresponding alkoxy acetates, however, did not exhibit a trend in parallel with the chemical structure. 2-Methoxypropionic acid was somewhat less cytotoxic than the alkoxy acetic acids investigated. It is concluded that gross cytotoxicity to dividing cells is not the predominant mechanism for the teratogenicity or myelotoxicity and testes toxicity of methoxy- and ethoxyethanol, which produce these effects after oxidation to their corresponding alkoxy acetates.