魚介類に存在する生理活性リン脂質 : 多価不飽和脂肪酸含有コリングリセロリン脂質の過酸化との関連

Abstract

Platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is a potent bioactive lipid that is formed enzymatically in various mammalian cells and tissues. We found that high PAF activities in lipid extracts from fishes. Recently, Tanaka et al. reported that novel phospholipids with an sn-2-short-chain acyl groups, having PAF-like bioactivities, were produced by lipid peroxidation of CGP (cholineglycerophospholipid) with an sn-2-polyunsaturated fatty acyl (PUFA) group. Therefore, we wondered whether the bioactive phospholipids in lipid extract from fishes were formed by lipid peroxidation. We extracted and prepared lipids with and without an anti-oxidant BHT from the tissues of various kinds of fishes and shellfishes. The lipid extract containing PAF-like compound that was purified by thin-layer chromatography induced the aggregation of washed rabbit platelets, and the activities were inhibited by PAF receptor antagonist, WEB-2086. Fishes which had high PAF-like activities were abundant in CGP with PUFA. In the case of lipid preparations without BHT, increase in PAF-like activities and TBARS (thiobarbituric acid-reactive substances) values, and decrease in PUFA content in CGP were observed. Furthermore, we peroxidized CGPs derived from various fishes and shellfishes, and PAF-like biological activities were measured by platelet aggregation. Investigations of the correlation between the PAF-like activities produced by peroxidation of PUFA containing CGP and the contents of PUFA and alkyl ether-linked subclass in parent CGPs, revealed that higher activities were produced by peroxidation of alky-PUFA CGP species, that were rich in alkyl ether-linked subclass and/or rich in docosahexaenoate (DHA). These results suggest that the lipids having PAF-like biological activities in fishes and shellfishes were produced by peroxidation of PUFA containing CGP.