ANALYSIS BY FAST-ATOM-BOMBARDMENT TANDEM MASS-SPECTROMETRY OF PHOSPHATIDYLCHOLINE ISOLATED FROM HEART MITOCHONDRIAL FRACTIONS - EVIDENCE OFINCORPORATION OF MONOHYDROXYLATED FATTY ACYL MOIETIES

Phosphatidylcholine (PC) is one of the main phospholipids present in m itochondrial membranes. According to current knowledge, the predominan t fatty acyl moieties in this phospholipid are 16, 18, 20, or 22 carbo n atoms long with chains that contain only carbon and hydrogen atoms. We have conducted a detailed analysis of the fatty acid substituents o f the phospholipids present in mitochondrial fractions by using fast-a tom bombardment tandem mass spectrometry. Six monohydroxylated C-16 an d C-18 fatty acyl moieties were found in PC extracted from mitochondri al fractions of rat heart. The structure of one of these monohydroxyla ted fatty acids has been elucidated and corresponded to 12-hydroxy 9-o ctadecenoic acid. indications that concern the structure of the five o ther monohydroxylated fatty acids are presented. These monohydroxylate d fatty acyl groups are preferentially associated in the PC molecule w ith C-18 and C-20 fatty acyl moieties. We present arguments to suggest that the formation of these compounds is probably not due to a free-r adical initiated mechanism. The potential implication of these monohyd roxylated fatty acids in several physiological functions is suggested by the fact that free hydroxylated fatty acids that are identical or c losely related to those found in the mitochondrial fractions possess v arious biological activities.