Kinetic study of deuterium-labelled polyenphosphatidylcholine after oral administration to rats

Deuterium-labelled di-[( 15,15,16,16-2H4]-linoleoyl) -3-sn-glycero-phosphocholine was used as a tracer of the major component of soybean polyene-3-sn-phosphatidylcholine to study the pharmacokinetics of a natural product after oral administration to rats. For this purpose a method was developed to isolate the phosphatidylcholine fraction from blood in a highly purified form. Only 200 pg deuterium-labelled fatty acid generated from the phosphatidylcholine fraction and a ratio of one molecule of deuterium-labelled stearic acid to 500 molecules of stearic acid are necessary for a reproducible measurement by gas chromatography/mass spectrometry. The highest amount of di-[( 15,15,16,16-2H4]-linoleoyl) -3-sn-glycerophosphocholine (0.12% dose/ml, i.e. 2.1% of the maximum absorbed dose) was detected in blood 6 h after administration. The results are comparable with those found after administration of di-[l-14C]-linoleoyl-3-sn-glycerophosphocholine. Hence it is possible to use deuterium-labelled polyenphosphatidylcholine instead of radioactively labelled polyenphosphatidylcholine, especially if a harmless tracer is required.