Positional distribution of fatty acids in cardiolipin of mitochondria from 21-day-old rats.

Pure cardiolipins (1,3-diphosphatidylglycerol) were prepared from mitochondria of heart, liver and kidney from 21-day-old male Wistar rats and submitted to Naja naja venom phospholipase A2 (EC 3.1.1.4) action. Incubation conditions were controlled carefully, and a complete hydrolysis of cardiolipin to lysocardiolipin (di [1 (1'') acyl sn-glycero-3-phosphoryl] 1',3'-sn-glycerol) and fatty acids from positions 2(2'') was obtained in less than two hr practically without side reactions. Cardiolipins from the three organs contained low levels of saturated fatty acids; stearic acid accounted for 0.4-0.7% and palmitic acid for 1.4-3.5% of total fatty acids. These percentages apparently depended on the organ. In all three cases, linoleic acid was the major component, but its percentage varied from 62-78% of total fatty acids. Acyl chains linked to positions 1 (1'') of all three cardiolipin preparations exhibited a similar pattern: they were composed of linoleic acid for 85-89%. This fatty acid also was the main component esterified at position 2 (2''), but its percentage was much more variable: from 39.8% in heart to 51.2% in kidney and 67.8% in liver mitochondria. The remaining acids comprised octadecenoic and polyunsaturated fatty acids with more than 18 carbon atoms in different proportions. As opposed to other phospholipids, cis-vaccenic acid, and not oleic acid, was the main octadecenoic acid present in cardiolipins. Octadecenoic acids were nine- to 10-fold more concentrated at positions 2 (2'') than at positions 1 (1''). The percentage of cis-vaccenic acid was four- to five-fold higher than that of oleic acid at positions 2 (2''), whereas oleic acid dominated at positions 1 (1'').(ABSTRACT TRUNCATED AT 250 WORDS)