Altered Cobalamin Distribution in Rat Hepatomas and in the Livers of Rats Treated with Diethylnitrosamine1

The distribution of cobalamin cofactors was investigated in the livers and tumors of rats bearing transplanted Morris 7777 or 7800 hepatomas, in the livers of rats treated with the hepatocarcinogen diethylnitrosamine, and in normal rats. There was a significant increase in the proportion of methylcobalamin both in livers and tumors from rats bearing the hepatomas 7777 and 7800 compared to the proportion of methylcobalamin in the livers of normal rats. The total co balamin content of the hepatomas was significantly lower than that of host or control livers. Similarly, the total cobala min content of the livers from the tumor-bearing rats was less than that in control animals. The administration to rats of an acute dose of diethylni trosamine led to an 84% increase in the hepatic concentra tion of methylcobalamin. Chronic administration of diethyl nitrosamine slightly increased the hepatic methylcobalamin concentration, but this was not statistically significant. Liver weight was reduced, and the hepatic content of total cobalamin fell to 55% of that in control animals.