The regulative role of food consumption in the induction of rat liver cell proliferation by drugs and environmental pollutants.

alpha-hexachlorocyclohexane (alpha-HCH) was used to stimulate cell proliferation in rat liver. Food consumption at two different stages of the replicative cycle was found to be required for the enhancement of DNA synthesis by this agent: (1) Before or at the time of alpha-HCH administration (G0), (2) 12--15 hours later, i.e. 5--8 hours before initiation of DNA synthesis ("R"-point). Other alpha-HCH mediated changes in the liver i.e. organ enlargement and the induction of drug-metabolising enzymes, remained unaffected by the absence of food. This suggests that the nutritional control is specific for induction of DNA synthesis. It is concluded that food consumption, in addition to specific stimuli of liver growth, is an exogenous regulator of liver cell proliferation.