Urinary excretion of thiodiglycollic acid and hepatic content of free thiols in rats at different levels of exposure to vinyl chloride.

In order to assess the process of oxidation and conjugation involved in biotransformation of vinyl chloride (VC), rats were exposed to 50, 200, 500, 1000 and 20,000 ppm inhaled VC. The rate of urinary excretion of thiodiglycollic acid (TDGA) after exposure to each investigated concentration of VC depends on the activity of microsomal monooxygenase. In general, higher levels of TDGA in urine were reflected by a more significant depression of non-protein sulfhydryl content in the liver of rats, whereas no changes were observed in those with inhibited activity of microsomal monooxygenase and depressed urinary levels of TDGA. The significance of alcohol dehydrogenase in the metabolism of low concentrations of VC has not been confirmed. Metabolism of VC in the range of 50--2 000 ppm is mediated by microsomal monooxygenase followed by conjugation with thiols.