The influence of fenarimol on DNA synthesis and mitotic activity in rat liver.

Fenarimol administered in one single oral dose of 125 or 62.5 mg kg-1 body wt. day-1, respectively, stimulated rat liver enlargement at a dose-independent rate. Three single doses of fenarimol produced dose-dependent liver growth, whereas five single doses caused no further increase in liver weight. This increase was accompanied by an increase in hepatic DNA synthesis and mitotic activity, with a peak on the first day after the beginning of the experiments. The increase in binuclear hepatocytes and signs of necrosis suggested that the hepatomitogenic effect reflected a compensatory hyperplasia. After both three and five single doses the hepatomitogenic effect was suppressed, as a result of tolerance development.