Characteristics of Hyperplastic Nodules in Rat Liver during 3'-Methyl-4-Dimethylaminoazobenzene Hepatocarcinogenesis. I. Histochemical Studies on Marker Enzymes of Endoplasmic Reticulum in Cells of Various Nodules

Male Wistar rats weighing 150-170 g were fed a solid diet containing 0.06% 3'-methyl-4-dimethylaminoazobenzene. After 12 weeks the carcinogenic diet was replaced with a normal solid diet. They were sacrificed at 2, 4, 6 and 8 weeks after withdrawal of the dye. Activities of glucose-6-phosphatase and nonspecific esterase in hyerplastic nodules in the liver were studied histochemically and biochemically in an attempt to elucidate the characteristics of hyerplastic nodules. The activity of glucose-6-phosphatase was markedly decreased in all hyperplastic nodules. On the other hand, most of the hyperplastic nodules showed elevated esterase activity, while a small number of nodules showed low esterase activity. The former were tentatively designated as Nodule I and roughly corresponded to reddish-brown nodules predominantly composed of cells with abundant eosinophilic cytoplasm. The latter were designated as Nodule II and corresponded to graysh-white nodules mostly composed of smaller cells with basophilic cytoplasm. The results of the histological, histochemical and biochemical studies suggest that the properties of the hepatocytes in Nodule II have some resemblance to those of liver cell cancer