The behavior of fat-soluble dyes in the organism

Abstract

It is well known that the fat-soluble dye, Sudan III., is readily deposited in the adipose tissue of animals. An attempt was made by the authors to study the movements of the dye under conditions where fat transport takes place (e. g., in starvation, phlorhizinand phosphorus poisoning). The dye readily migrates into the blood with the fat under these conditions, but is rarely found in the liver tissue into which large quantities of fat enter (fatty infiltration). This is explained by the observation that the Sudan III. is abundantly excreted with the bile into the intestine from which it may be reabsorbed. Sudan III., which is insoluble in water, is not excreted through the kidneys except where alimentary lipuria is induced (in rabbits and rats). The elimination from the liver is not accomplished through the solvent medium of fat excreted in the bile (lipocholia); but the dye is soluble in bile as well as in solution of the isolated bile salts. We have thus established a path of elimination for fat-soluble (or bile-soluble) substances through the biliary secretion. An investigation of a considerable number of water-insoluble, fat-soluble compounds—mostly nontoxic aniline dyes and food colors—showed comparable conditions justifying the above general conclusion. It has further been established that these water-insoluble compounds do not experience absorption from the intestine in the absence of bile. Dissolved in fat-emulsion and introduced into the organism by alimentary, subcutaneous, or intravenous paths, these dyes are always eliminated with the bile into the intestine. When there is a paucity of fat in the diet the fat-soluble dyes may be absorbed through the agency of reabsorbed bile, but they are speedily eliminated again by the liver channels; with an abundance of fat to act as carrier, they travel with it through the lymphatics into the circulation.