Interrelationship between bile lecithin and liver lecithin newly synthesized through phosphatidic acid pathway.

Abstract

1) Liver, plasma and bile lecithins of male Wistar rats were separated to subfractions of different degrees of unsaturation by AgNO3 Silica Gel-thin layer chromatography and their fatty acid compositions were analyzed by gas chromatography. 2) Specific activities of liver, plasma and bile lecithins and their subfractions were determined at various time periods from 10 to 240min following the intraportal injection of radioactive glycerol, choline and linoleic acid as precursors. Among subfractions, the highest values were found in either dienoic or monoenoic-dienoic subfractions of bile, plasma as well as liver lecithins. The values of bile lecithin or its subfractions were higher than those of liver or plasma lecithins or their subfractions respectively. 3) The turnover time of plasma lecithin was 66 or 55 min up to 120 min following the injection of glycerol or choline. The values of subfractions were 50, 48 and 37 min in monoenoic-dienoic, tetraenoic and hexaenoic ones, using choline as precursor. 4) The mean value of specific activity ratio (bile/liver) was 4.0 or 2.6 on total lecithin at time intervals from 0 to 120 min after the injection of glycerol or choline. The values with choline were 2.5, 1.7 and 1.2 in three different subfractions, respectively. 5) The secretion rate constants of bile lecithin calculated from nonisotopic as well as isotopic data were in the range of 0.009 and 0.036. The values were 0.016-0.043, 0.004-0.010 and 0.006-0.014 in three subfractions, respectively. 6) The data suggested that the marked differences regarding molecular species of fatty acid composition between bile and liver lecithins could be ascribed to the preferential uptake of α-palmitoyl β-linoleoyl (or oleoyl) species by a bile forming site from a minor dynamic pool different from a major static pool of liver lecithin. While the plasma lecithin may be produced from the static pool but not directly from the dynamic pool.