Histochemical comparison of focal losses of RNase and ATPase activities in preneoplastic rat livers.

To better assess the significance of enzyme-deficient foci as putative premalignant lesions, parallel histochemical analyses of RNase and ATPase activities were carried out in serial sections of livers from rats fed 4-dimethylaminoazobenzene. The results showed that focal losses of RNase and canalicular ATPase activities occur simultaneously in congruent areas of liver parenchyma at early stages of carcinogenesis. Such foci presumably represent altered cells capable of progressing to neoplasia since the changes observed in this new cell population persist in developing tumors.