Studies on liver phosphatidyl cholines: II. Effect of sex, age and species differences on phosphatidyl cholines from liver mitochondria and microsomes

Liver mitochondrial and microsomal phosphatidyl cholines differing in the degree of unsaturation of their fatty acids have been separated into four fractions by silver ion silica gel TLC. The levels of the four phosphatidyl choline fractions were determined for male and female rats and mice, fetal and young rabbits, and female hamsters and guinea pigs. The sum of phosphatidyl choline fractions 1, 2, and 3 of mitochondria and microsomes was greater in the female rat than in the male rat with the difference being a reflection of a higher level of fraction 3 which contains arachidonic acid. The female rat has greater concentration of phosphatidyl choline fractions 1 and 3 of mitochondria. Similar results were seen in mouse liver microsomes but not in mitochondria. The levels of the individual four fractions varied from species to species. No change occurred in the levels of the phosphatidyl choline fractions of fetal (−9 and −3 days) rabbits, but an increase was seen in the level of fraction 4 between day 3 and day 35 in both the mitochondria and microsomal fractions of liver. The concentration of mitochondrial and microsomal protein, total phospholipid and total lecithin phosphorus were determined in rat, mouse, hamster and guinea pig. The total phospholipid phosphorus/protein (μg/mg) of microsomes was greater in all species than that observed in mitochondria. Liver microsomes contain 45–50% of total phospholipid phosphorus as lecithin whereas mitochondria contains 32–37%. The fatty acid patterns of mitochondria and microsomal phosphatidyl cholines were determined and the ratio of palmitate to stearate was greater than two for mice and hamsters and approximately 0.5 for rat and guinea pigs.