[Detection of cells resistant to the cytotoxic action of CCl4 in rat hepatocyte populations following a single exposure to diethylnitrosamine and subsequent injections of phenobarbital].

A single intraperitoneal injection of hepatocarcinogen diethylnitrosamine induced emergence of a new subpopulation of "small" hepatocytes (64-128 mkm2), disappearing by the 30th day after carcinogen injection. But 5 injections of the tumor promotor phenobarbital 7 days after carcinogen treatment prolonged the existence of such "small" hepatocytes up to 3 months. The quantitative cytochemical measurement of succinic dehydrogenase activity (respiratory enzyme of mitochondria) showed these cells to be resistant to cytotoxic action of CCl4. These data are consistent with the earlier reported results obtained in analogous experiments with 4-dimethylaminoazobenzene and phenobarbital.