The potential reversibility of glandular stomach lesions induced by the clastogen, catechol, was examined in groups of male F344 rats treated continuously with 0.8% catechol in the diet for 12, 24, 48, 72, or 96 weeks. After a return to basal diet for 84, 72, 48, 24, and 0 weeks, respectively, the animals were killed for histopathological examination. Incidences of submucosal hyperplasia, adenomas and adenocarcinomas, average number of tumors per rat, and the size of tumors in rats treated with catechol for 12, 24, 48, 72, and 96 weeks increased time dependently. After cessation of catechol treatment, although average number of tumors per rat slightly decreased, the size of tumors tended to increase. Labeling indices in both tumorous and nontumorous areas decreased after cessation of catechol treatment. The results thus indicate that whereas some submucosal hyperplasias or adenomas may regress, others have the potential to develop into adenomas or adenocarcinomas. However, tumor growth does depend to a certain extert on continued catechol treatment.

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This work was supported by a Grant-in-Aid for Cancer Research from the Ministry of Education, Science and Culture, Japan; a grant from the Ministry of Health and Welfare, Japan; a grant from the Society for Promotion of Pathology of Nagoya, Japan; and a grant from the Experimental Pathological Research Association, Japan.

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