METABOLISM OF CEREBROSIDE IN INTESTINAL TRACT OF RAT

[3-3H]Sphingosin- or [9,10-3H2]palmitoyl-labeled glucosyl-ceramide and [6-3H]-galactosyl-labeled galactosyl-ceramide were fed to intact rats and to rats with a thoracic duct fistula. The data obtained from analyses of the thoracic duct lymph, of the small intestine and intestinal contents and of the feces indicated that to a large extent the substrates were absorbed and metabolized in the small intestine. 20-42% of the fatty acid portion was recovered in lymph triglycerides and lecithin, and labeled hexose was transported in a water-soluble form by the portal vein. The low recoveries of radioactivity in lymph lipids in experiments with [3-3H]sphingosin-labeled glucosyl-ceramide and earlier data indicated that 55-60% the sphingosin portion was absorbed and metabolized to fatty acids in the mucosal cells. The remainder appeared in the feces as intact cerebroside and ceramide. Rat pancreatic juice and human intestinal contents did not hydrolyze glucosyl-ceramide. The analyses of the small intestine and intestinal contents 2-3 h after feeding the substrates also indicated that the hydrolysis of dietary cerebroside occurs in the mucosal cells after absorption. An active biosynthesis of cerebroside, in which dietary sphingosin bases take part, occurs in the mucosal cells. © 1969.