Biosynthesis of phytosphingosine by the rat.

Labeled C18-phytosphingosine was detected in a glyco-lipid-rich fraction from rat intestine 4 and 24 h after injection of D-erythro[4,5-3H]C18-dihydrosphingosine. The criteria for identification were: (a) co-migration on gas-liquid chromatography of the trimethylsilyl ethers of the free and N-acetylated base with authentic standard, (b) co-migration on thin layer chromatography of the dinitrophenyl derivative with authentic standard, (c) labeled pentadecanol detection by gas-liquid radiochromatography after subjecting intact sphingolipids or a mixture of free long chain bases to periodate oxidation followed by sodium borohydride reduction, and (d) obtainment of the same fragmentation pattern as with authentic standard when the trimethylsilyl ethers of the N-acetylated base were subjected to gas-liquid chromatography-mass spectrometry. Smaller amounts of labeled C18-phytosphingosine were also detected in ceramide- and sphingomyelin-rich fractions of intestine and in liver and kidney. Experiments with germ-free rats strongly suggest that the intestinal flora is not the (sole) site for the biosynthesis of C18-phytosphingosine.