Quantitative electron microscopic analysis of changes in peroxisomes and endoplasmic reticulum induced in mice during hepatocarcinogenesis by diethylnitrosamine promoted by di(2-ethylhexyl)phthalate or phenobarbital.

Histochemical studies have shown that basophilic adenomas and carcinomas develop from basophilic foci in mice initiated with N-nitrosodiethylamine (DEN) and promoted by di(2-ethylhexyl)phthalate (DEHP), whereas eosinophilic liver tumors promoted by phenobarbital (PhB) arose from eosinophilic foci. In this experiment, the ultrastructure of tumorous and nontumorous areas of the liver from these two groups of mice was analyzed by quantitative morphometric methods. It is shown that nontumorous liver in DEN- and DEHP-treated mice demonstrate a pronounced proliferation of peroxisomes that is also present in liver tumors induced by DEHP alone but not in liver tumors after DEN initiation and DEHP promotion. Initiation with DEN and promotion with PhB resulted in pronounced proliferation of smooth endoplasmic reticulum (ER) in both tumorous and nontumorous liver, whereas the number of peroxisomes remained unchanged.