Diet and Azo Dye Tumors: a Period When the Dye is Not Fed*

Although it is @ve11 recognized that rats fed azo dyes develop tumors at rates that depend upon the diet fed with the dye (@28), the mechanism by which this is accomplished is unknown. One possi bility is that pertinent diets alter the metabolism of the dye and thus alter the concentration of ef fective carcinogen; another, that diet can effect changes in normal cellular constituents that either enhance or minimize the sensitivity of the tissue to the carcinogen. Still another possibility is that appropriate diets might modify those phases of the carcinogenic process that continue after the car cinogen is no longer present in the tissues. Dietary effects in the latter categories would have a wider significance in the cancer problem than those in the first. Accordingly hepatic tumors were induced in rats by the feeding of a synthetic ration contain ing the potent azo dye, m'-methyl-p-dimethylami noazobenzene (m'DAB), interrupted by the feed ing of experimental diets containing no dye. In a few ijarallel studies the riboflavin contents of the livers and the coagulability of liver homogenates were also measured.