Biochemical and toxicological effects of combined exposure to 1,1,1-trichloroethane and trichloroethylene on rat liver and brain.

1. Inhalation exposure of adult male rats to a mixture of 1,1,1-trichloroethane (500 p.p.m.) and trichloroethylene (200 p.p.m.) for four days 6 h daily resulted in an accumulation of 1,1,1-trichloroethane in perirenal fat. Further exposure on the fifth day caused a rapid increase in various organ contents of both solvents with secondary depression of brain RNA. 2. The four-day exposure doubled the RNA content of liver and caused a slight decline in the concentrations of glutathione in liver. 3. The amount of cytochrome P-450 in liver was increased, as well as the overall mono-oxygenase activity, measured with styrene as substrate. During continuing treatment on the fifth day, styrene mono-oxygenase activity decreased, the activity after 6 h being only about 50% of that at the beginning of the fifth day of exposure. 4. UDP-glucuronosyl transferase activity (measured in digitonin-activated microsomes) was doubled by the four-day combined exposure to 1,1,1-trichloroethane and trichloroethylene. 5. The changes during the fifth day of exposure, e.g. rapid increase in the concentrations of solvents in organs, the detection of trichloroethylene in tissues and depression of mono-oxygenase activity, obviously also occurred during the exposures on days 1 to 4 and reverted during each post-exposure period.