Enzymatic and Immunological Studies on Pyruvate Carboxylase in Livers and Liver Tumors¹ Free

It was found that one Reuber hepatoma and seven Morris hepatomas with different growth rates and various degrees of differentiation contained pyruvate carboxylase (PC) activity ranging from 3 to 113% of control values. The levels of PC activity in the regenerating liver, spontaneous mouse hepatoma, and host livers of tumor-bearing rats were estimated in the range of normal rat liver. In the group of tumors studied, two hepatomas of intermediate growth rate and four highly and well-differentiated, slow-growing tumors, like rat fetal liver, had negligible or little PC activity. However, one hepatoma, 9618A, had a normal level of PC activity. Antibodies prepared in rabbits against the purified mitochondrial enzyme showed identical titration curves against the nuclear and cytosol PC of liver. A single continuous precipitation line was obtained on Ouchterlony double-diffusion precipitation analysis when purified mitochondrial enzyme, crude mitochondrial preparations of rat tissues and hepatomas, were compared. It was also found that the immunological, enzymatic, and electrophoretic properties of the tumor PC were the same as those of normal adult and newborn rat liver. The amount of enzyme protein was quantitatively reduced in all but one of the liver tumors studied.