Fonteh A N, Chilton F H
Bowman Gray School of Medicine of Wake Forest University, Winston-Salem, NC 27157-1054.
J Immunol. 1993 Jan 15;150(2):563-70.
Immunologic activation of mast cells leads to the mobilization of arachidonic acid (AA) from membrane phospholipids and the subsequent conversion of this AA to bioactive products. The objective of our study was to determine if segregated pools of AA-containing phospholipids within mast cells serve as independent sources of AA. Initial studies indicated that the appearance of free AA occurred rapidly (maximal level formed within 1 min) within supernatant fluids of Ag-stimulated mast cells and was kinetically different from the formation of leukotriene (LT) B4 or LTC4. To examine whether free AA and leukotrienes were mobilized from different sources, AA-containing phospholipids of mast cells were labeled with [14C] and [3H] AA such that all major subclasses (1-acyl-1-alkyl-1-alk-1'-enyl) of phospholipids contained different ratios of [3H] to [14C] (sp. act. ratios (SAR)). Mast cells were then stimulated with Ag and the SAR of cellular AA, extracellular AA and extracellular LTC4, LTB4, 6-trans LTB4, were determined. The SAR were uniform in all LT and mimicked the ratio found in cellular AA. By contrast, the SAR of AA released into supernatant fluids was twofold lower than that of LT. This indicated that AA released as free fatty acid clearly was derived from a different lipid pool than AA that formed LT. Although it was apparent that the pools which gave rise to AA and LT were different, defining phospholipid(s) that constitute these distinct pools proved more difficult. The SAR of LT suggested that their cellular precursor AA could have been derived from several phospholipid subclasses; however, the SAR in phosphatidylcholine and phosphatidylinositol most closely matched the LT. The SAR of AA in supernatant fluids implied that it was derived, in part, from phosphatidylethanolamine subclasses. Taken together, these data suggest that there are at least two different pools of AA that are mobilized in mast cells during Ag activation.
肥大细胞的免疫激活导致花生四烯酸（AA）从膜磷脂中动员出来，并随后将该AA转化为生物活性产物。我们研究的目的是确定肥大细胞内含有AA的磷脂分隔池是否作为AA的独立来源。初步研究表明，游离AA在抗原刺激的肥大细胞的上清液中迅速出现（在1分钟内形成最大水平），并且在动力学上与白三烯（LT）B4或LTC4的形成不同。为了检查游离AA和白三烯是否从不同来源动员，肥大细胞中含AA的磷脂用[14C]和[3H] AA标记，使得所有主要亚类（1-酰基-1-烷基-1-烯基）的磷脂含有不同比例的[3H]与[14C]（比活性比率（SAR））。然后用抗原刺激肥大细胞，并测定细胞内AA、细胞外AA和细胞外LTC4、LTB4、6-反式LTB4的SAR。所有LT中的SAR是一致的，并且模仿了细胞内AA中发现的比率。相比之下，释放到上清液中的AA的SAR比LT低两倍。这表明作为游离脂肪酸释放的AA显然来自与形成LT的AA不同的脂质池。虽然产生AA和LT的池明显不同，但确定构成这些不同池的磷脂更加困难。LT的SAR表明它们的细胞前体AA可能来自几个磷脂亚类；然而，磷脂酰胆碱和磷脂酰肌醇中的SAR与LT最匹配。上清液中AA的SAR表明它部分来自磷脂酰乙醇胺亚类。综上所述，这些数据表明在抗原激活期间肥大细胞中至少有两个不同的AA池被动员。
