The effect of cupric oxyacetate on the binding of azo-dye by protein during the induction of liver tumours in the rat

Abstract

When maize containing 0.09% of the liver carcinogen 4-dimethylaminoazobenzene was given to albino rats, the amount of azo-dye bound to liver protein rose to a maximum after 100 days and then progressively decreased. When the diet also included 0.5% of cupric oxyacetate, the maximum amount of azo-dye bound appeared to be slightly less and the time to attain it was doubled. When the diet containing azo-dye was given, liver copper was increased by 40% after 315 days, and about three-quarters of this extra copper was bound to protein. When the diet contained the cupric oxyacetate in addition the copper content was increased 40-fold at 330 days. For the first 200 days, most of this stored copper was bound to protein. After this time, further copper was only held loosely in the organ and the bound copper maintained a steady "saturation" level of 10 times the normal amount. The results are discussed with respect to the mechanism by which copper delays the induction of liver tumours by the azo-dye.