Joly F, Breton M, Wolf C, Ninio E, Colard O
INSERM U 200, Clamart, France.
Biochim Biophys Acta. 1992 May 8;1125(3):305-12. doi: 10.1016/0005-2760(92)90060-9.
In mammalian cells, arachidonate release and paf-acether formation are frequently associated. The alkyl-acyl-GPC has been proposed as an important source for released arachidonic acid and arachidonate-containing alkylacyl-GPC species as unique precursor for paf-acether. However, the specificity of precursor pools either concerning arachidonic acid or paf-acether is still a matter of controversy. We studied the relationship between the precursor pools for both autacoids in antigenically-stimulated cultured mast cells. We took advantage of the particular arachidonate turnover rate in each phospholipid to investigate the role of alkyl-arachidonyl-GPC in the supply of arachidonic acid by using newly and previously [14C]arachidonate-labeled cells. The specific activity of the released arachidonate was reduced 2-fold following overnight cell incubation, whereas labeling in alkyl-arachidonoyl-GPC was only slightly modified and never corresponded to that of released arachidonate when newly or previously labeled cells were triggered with the antigen. These results are not in favor of a major role for alkyl-arachidonoyl-GPC in supplying arachidonate. In contrast, by using previously labeled cells, we demonstrated that all arachidonate-containing phospholipids were involved in the release of arachidonic acid. The pattern of alkyl chains in alkyl-arachidonoyl-GPC, as well as in total alkylacyl-GPC, is unique since it consists mainly of 18:1 (more than 55%), whereas the 16:0 represents only about 30% of total alkyl chains. Therefore, we analyzed paf-acether molecular composition in order to compare it to the alkyl composition of the precursor pools. The content in 18:1 species of paf-acether, as measured by bioassay (aggregation of rabbit platelets), was always lower than that of 16:0 species and then did not correspond to the alkyl composition of the precursor. These data suggest that the enzymes involved in paf synthesis might be specific for 16:0 alkyl chains of precursor pool.
在哺乳动物细胞中，花生四烯酸释放与血小板活化因子（PAF - 乙酰基醚）形成常常相关。烷基 - 酰基 - 甘油磷脂酰胆碱（alkyl - acyl - GPC）被认为是释放的花生四烯酸的重要来源，而含花生四烯酸的烷基酰基 - GPC种类是PAF - 乙酰基醚的独特前体。然而，关于花生四烯酸或PAF - 乙酰基醚的前体池的特异性仍然存在争议。我们研究了抗原刺激的培养肥大细胞中这两种自分泌物质的前体池之间的关系。我们利用每种磷脂中特定的花生四烯酸周转率，通过使用新的和先前用[14C]花生四烯酸标记的细胞来研究烷基 - 花生四烯酰 - GPC在花生四烯酸供应中的作用。过夜细胞孵育后，释放的花生四烯酸的比活性降低了2倍，而当新标记或先前标记的细胞用抗原触发时，烷基 - 花生四烯酰 - GPC中的标记仅略有改变，且从未与释放的花生四烯酸的标记一致。这些结果不支持烷基 - 花生四烯酰 - GPC在供应花生四烯酸中起主要作用。相反，通过使用先前标记的细胞，我们证明所有含花生四烯酸的磷脂都参与了花生四烯酸的释放。烷基 - 花生四烯酰 - GPC以及总烷基酰基 - GPC中的烷基链模式是独特的，因为它主要由18:1（超过55%）组成，而16:0仅占总烷基链的约30%。因此，我们分析了PAF - 乙酰基醚的分子组成，以便将其与前体池的烷基组成进行比较。通过生物测定（兔血小板聚集）测量的PAF - 乙酰基醚中18:1种类的含量总是低于16:0种类的含量，因此与前体的烷基组成不对应。这些数据表明，参与PAF合成的酶可能对前体池的16:0烷基链具有特异性。
