DOSE EFFECTS ON THE EXCRETION OF URINARY METABOLITES OF 2-[1,2,METHOXY-C-13]METHOXYETHANOL IN RATS AND MICE

The administration of 2-methoxyethanol (2-ME) to pregnant rats, mice, or primates results in developmental toxicity. To assess the role of m etabolism in the adverse response of 2-ME, carbon-13 NMR spectroscopy was used to examine, directly in the urine, metabolites produced after administering high (250 mg/kg) and low (25 mg/kg) doses of 2-[1,2,met hoxy-C-13]ME to pregnant CD-1 mice and male Fischer 344 rats. The high dose elicits teratogenic effects in mice and testicular toxicity in r ats. The urinary disposition was also examined after dosing pregnant C D-1 mice with a developmentally toxic level of 2-ME together with seri ne or acetate (known attenuators of 2-ME embryotoxicity). Seven novel metabolites were found in rat urine, consistent with those assigned in our previous studies with mice. Metabolite composition was compared f or the different dosing regimens. A lower percentage of metabolites de rived after conversion of 2-ME to 2-methoxyacetic acid (2-MAA) was fou nd following concurrent administration of 2-ME with acetate, D-serine, or L-serine, These differences are mainly attributed to higher levels of ethylene glycol and/or glycolic acid that arise for the 2-ME admin istrations with any of the attenuators. Acetate together with 2-ME als o reduced the percentage of metabolites incorporated into intermediary metabolism. These data indicate that attenuators of 2-ME teratogenic effects may alter metabolism and distribution by decreasing the conver sion of 2-ME to 2-MAA, decreasing the conversion of 2-MAA to a coenzym e A thioester (2-methoxyacetyl similar to CoA), altering the utilizati on of the coenzyme A thioester, and/or increasing the conversion of 2- ME to ethylene glycol and its further metabolism. These changes in met abolism may contribute to the attenuating effects of these agents on 2 -ME. (C) 1995 Academic Press, Inc.