The Metabol ism of Ethionine in Rats I

The L-[ethyl-l-14C]ethionine metabolites soluble in trichloroacetic acid were studied in rats by the use of column chromatography. After p.o. application of ethionine, its absorption from intestinal lumen was rapid and was complete in less than 2 hr. Any unabsorbed ethionine was later excreted in the feces. During the passage through the gastrointestinal tract, a portion of ethionine was metabolized. The chemical nature and biological significance of these metabolites is not yet known. The fate of absorbed ethionine was investigated in the small intestine, liver, blood, kidney, and urine as a function of time after application. A great part of ethionine was quickly oxidized to ethionine sulfoxide. In liver and kidney, the concentration of ethionine sulfoxide was higher than that of free ethionine. In all organs, the presence of N-acetylethionine sulfoxide was also demonstrated. Ethionine sulfoxide can be reduced and N-acetylethionine can be deacetylated in vivo as demonstrated by the formation of S-adenosylethionine from ethionine sulfoxide and N-acetylethionine. In urine, 4 main components were observed: N-acetylethionine sulfoxide, S-adenosylethionine, ethionine sulfoxide, and free ethionine. Some minor components, as yet unidentified, were also present in the urine and in different organs. The probable site of origin of urinary S-adenosylethionine is the kidney.