Effect of chloroform on hepatic and renal DNA synthesis and ornithine decarboxylase activity in mice and rats.

Chloroform administered intraperitoneally (i.p.) to male mice and rats resulted in a dose-dependent increase in hepatic ornithine decarboxylase (ODC) activity. Maximal induction of the enzyme in mice was 10-fold and occurred at 375 mg/kg chloroform; in rats it was 52-fold and occurred at 750 mg/kg chloroform. Chloroform increased in mice and decreased in rats the rate of hepatic and renal DNA synthesis. Therefore, the induction of ODC activity in rat liver was not followed with an increase in DNA synthesis. The implications of these results to the proposed nongenetic mechanism of chloroform induction of hepatocellular carcinoma in mice and renal tumors in rats are discussed.