Studies on azo-dye carcinogenesis in rat liver. The effect of 4-dimethylamino-3′-methylazobenzene on the incorporation of [14C]leucine into rat-liver microsomal protein

Publisher Website
Google Scholar
Abstract
The incorporation of [14C]leucine into protein by a system consisting of washed microsomes plus pH 5 enzyme was studied at various times after a single intraperitoneal injection of 4-dimethlamino-3[image]-methyl-azobenzene. Both the rate of incorporation and the specific activity of the microsomes showed an increase after 20 hr., reaching a maximum at 40 hr., and thereafter returned to normal. The incorporation of [14C]leucine into the microsomal protein of mitochondrial super-natants was also studied after the administration of 4-dimethylamino-3[image]-methylazobenzene. Considerable inhibition of incorporation was found 4 hours after the administration of the dye, with a return to normal after this time. The specific activities of microsomes isolated from mitochondrial supernatants were always considerably lower than those of washed preparations. An inhibitor of the incorporation of [14C]-leucine was found in both the normal pH 5-supernatant and "azo"-pH 5-super-natant fractions. The "azo"-microsomal incorporating system was affected by both supernatant fractions to a much greater extent than was the normal microsomal incorporating system. The inhibitor was diffusible. Fractionation of the pH 5 supernatant of homogenates from azo-dye-treated rats with ammonium sulphate gave three fractions that all stimulated the incorporation of [12C]leucine. These fractions were also able to replace the pH 5-enzyme fraction to a certain extent.