14C-labelled trichloroethylene was injected i.p. into male mice (10 mumole/g of b.w.). The radioactivity irreversibly bound to hepatic protein reached highest levels after 6 h: 2 nmole/mg in cytosol protein, 4.4 nmole/mg in mitochondrial protein, and 7.6 nmole/mg in microsomal protein. 2. The commercial trichloroethylene contained radioactive impurities binding to proteins without metabolic activation. Purification by various extractions removed 60-70% of those materials. In aerobic incubates of mice hepatic microsomes and NADPH the covalent binding rate of the purified trichloroethylene was 1.4 nmole/mg protein in 60 min. The activity of rat liver microsomes was approximately 40% less. Covalent binding increased 2-fold with microsomes of mice pretreated with phenobarbital.
