Choline Deficiency, Partial Hepatectomy, and Liver Tumors in Rats and Mice.

Choline deficiency (CD) increases susceptability of (he rat liver to a number of hepatocellular carcinogens with a wide diversity of structure and potency. While severe CD results in micronodular cirrhosis and enhanced tumor induction, even a mild deficiency, without cirrhosis is sufficient to result in the increased carcinogenic response. The effects of CD are in part mediated via modulation of microsomal and, possibly, cytosolic enzymes responsible for activation/deactivation of carcinogens. The B6C3F1 hybrid mouse is remarkably sensitive to initiation/promotion of liver tumors by many substances or conditions. Choline deficiency or partial hepatectomy alone, or in concert, markedly enhances liver tumor induction in the absence of any known carcinogen. These data indicate that the liver of this strain of mouse is "initiated" at or shortly after birth and can be promoted by non-carcinogenic substances or conditions.