Effect of pretreatment of rats with carbon tetrachloride on tolerance development ToxicoL

pretreatment of rats with CCL, on tolerance development to subsequent exposures, rats were exposed 25-7500 ppm of CC & vapor or given Ccl, orally, 3.25 mg/g body weight. Forty-eight hours later these rats were rcexposed to a normally lethal 7500 ppm Ccl0 concentration. Mortality, blood clotting time, serum bilirubin, serum and liver triglycerides, and CC & and CHC & concentrations in tissues and in the whole rat were used as a measure of the response to Ccl, exposure. Conversion of Ccl., to CHCl3 in vitro was also determined in normal and pretreated animals. It was found that animals exposed to 4000 ppm for 6 hr or given 3.25 mg/g of CC & orally developed tolerance to subsequent normally lethal CC & exposures. Serum bilirubin levels in animals protected by CCI, pretreatment were significantly lower than in those receiving only a single exposure to Ccl,. Blood clotting times in protected animals were normal, while in those not protected by pretreatment, they were greatly prolonged. Serum triglyceride levels in protected animals were normal whereas they were considerably depressed i