The effect of dietary fat on the molecular species of lecithin from rat liver

1. 1. Lecithins from the liver of rats maintained on diets devoid of essential fatty acids or supplemented with coconut oil or corn oil revealed significant differences in fatty acid composition, whilst monomolecular films of these lecithin samples exhibited only limited differences in force-area characteristics. 2. 2. The individual molecular species in the three lecithin samples were determined by means of the following techniques: (a) fractionation of the lecithin on silica impregnated with silver nitrate, followed by determination of the positional distribution of the fatty acids with snake-venom phospholipase A (EC 3.1.1.4); (b) hydrolysis of the lecithin with phospholipase C (EC 3.1.4.3) from Bacillus cereus and fractionation of the resultant diglycerides on silica impregnated with silver nitrate. Subsequently, the positions of the fatty acid constituents in the diglyceride fractions were determined by hydrolysis with pancreatic lipase (EC 3.1.1.3). The second approach gave the most detailed information and made it possible to recognize between 14 and 23 species. Quantitative determination of the major species accounted for 78.5 to 90.5% of the molecular composition. 3. 3. Differences in diet induced significant variations in the proportions of the various lecithin species and also brought about qualitative differences. These shifts in the molecular composition of the lecithin samples may contribute to preserving the liquid-crystalline nature of these lipids in membrane structures