The effects on mouse and monkey liver of long-term oral administration of chlorobiphenyls (CBP), 1.5 mg/day or more, have been investigated at selected intervals by light and electron microscopy. Hepatocytes of mice contained large amounts of acidophilic materials in the cytoplasm" and fatty vacuoles were observed later. Fine structural changes in the hepatocytes consisted of a marked increase of smooth endoplasmic reticulum, a reduction of rough endoplasmic reticulum, "myelin figure" formation in the cyto-plasm, and increase of microbodies and Iysosomes. A marked increase in lipid droplets was observed later. Results of electron microscopy in monkey liver showed an increase of smooth en"" doplasmic reticulum in the hepatocytes and swelling of Kupffer’s cells, with an increased number of Iysosomes and vacuoles. Judging from the findings by electron microscopy, characteristic lesions of liver cells were produced by administration of CBP.
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