Characterization of gastric mucosal membranes. II. Lipid compositions of purified gastric mitochondria from pig, rabbit and frog.

1. The lipid composition of purified mitochondrial fractions from the fundic mucosa of pig, rabbit and frog were determined. 2. The total lipids expressed as mg lipid per 100 mg mitochondrial protein were approx. the same in pig and rabbit (13.4 and 15.5, respectively) and much higher than in frog (8.5). 3. The levels of phospholipids were about the same in pig and frog (approx. 61% of the total lipid) and lower than rabbit (78%). However, the levels of cholesterol were significantly different in the three species and constituted 22, 9 and 18.2% of the total lipids in pig, rabbit and frog mitochondria, respectively. 4. The glycolipid content in the mitochondrial lipids from pig, rabbit and frog were 7, 5.6 and 10.5%, respectively. 5. Cardiolipin contributed from 5.6 to 7.5% of the total phospholipids in the various species. Phosphatidylethanolamine and phosphatidylcholine together accounted for 80 90% of the total phospholipids in the various species; the contribution of phosphatidylcholine being always higher than that of phosphatidylethanolamine. Small but significant amounts of phosphatidylinositol were present in all species. 6. Generally, the predominant saturated fatty acid in the phospholipids was 16:0 from all species (except in phosphatidylethanolamine from pig and frog), and 18:1 and 18:2 were the predominant unsaturated fatty acids from all species. Sphingomyelin contained the highest amount of saturated fatty acids (over 80%) in both the species (pig and rabbit) studied.