Continuous inhalation of 5000 ppm CH2Cl2 caused balloon degeneration, transient severe fatty change and partial inhibition of leucine incorporation into liver proteins of 20-32 g female mice of the ICR stain. The earliest lesion was identified at 12 hr of exposure and consisted of dissociation of polyribosomes and swelling of hepatocyte rough endoplasmic reticulum (so-called "balloon" degeneration). Balloon degeneration peaked in severity at 2 days of exposure and then partially reversed. Liver fatty change was also partially reversible. There was a 12-fold increase in liver triglycerides with 3 days of exposure, but at 1 wk of continuous exposure liver triglycerides were two to three times control values. Necrosis was observed in a few isolated hepatocytes. The reversibility of the liver changes suggests that partial tolerance develops in hepatocytes with continuous exposure to 5000 ppm dichloromethane. Liver lesions produced in the mouse liver by dichloromethane bear some resemblance to the lesions of carbon tetrachloride hepatotoxicity but appear to be less severe.
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