Peroxisomes in hepatomas and hyperplastic preneoplastic liver lesions induced in mice by 500 ppm α-benzene hexachloride were examined histochemically and electron microscopically. Although most of the hepatomas were well-differentiated tumors and contained a considerable number of peroxisomes, the tumor cells did not respond to ethyl-α-p-chlorophenoxyisobutyrate with proliferation of peroxisomes. At the 16th week of carcinogen feeding, hyperplastic nodules appeared and advanced to further stages. A majority of the nodules showed a considerable number of peroxisomes and the inductive proliferation of peroxisomes. Within the nodules, foci of proliferation of the cells that showed no inducibility of proliferation of peroxisomes appeared. These cells proliferated further, replacing the most part of the nodules, and with this process hepatomas appeared to have been formed. No abnormal matrical inclusions of peroxisomes were formed in the cells of hyperplastic nodules by ethyl-α-p-chlorophenoxyisobutyrate unlike in the case of rats.

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Supported in part by grants-in-aid 101059, 101062, and 201058 for Cancer Research from the Ministry of Education, Science and Culture, Japan.

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