Ramesha C S, Pickett W C
J Immunol. 1987 Mar 1;138(5):1559-63.
The molecular heterogeneity of platelet-activating factor (PAF) synthesized by unstimulated and Ca2+ ionophore (A23187)-stimulated PMN from rat, mouse, and guinea pig and by rat basophilic leukemia (RBL) cells was investigated by gas chromatography-negative ion chemical ionization mass spectrometry. Several molecular species of PAF ranging from C14:0 to C19:0 were detected in all of the cells studied. PAF produced by each cell type exhibited a unique pattern of molecular species distribution. Although C16:0 was the major PAF molecular species of rat PMN and RBL cells representing 96% and 85% of the total PAF, respectively, PAF from mice PMN contained 81% of C16:0, 10% of C18:1, and 6% of C18:0. Alternatively, A23187-stimulated guinea pig PMN yielded PAF molecular species 35% in C16:0, 35% in C17:0, 8% in C18:1, and 3% in C18:0. Small but significant differences in the PAF molecular species distribution of resting and ionophore stimulated cells were also observed. In contrast to the PAF molecular species composition, the precursor 1-O-alkyl-2-acyl-glycero-3-phosphocholine of all the cell types was predominantly hexadecyl (C16:0) alkyl chain in the sn-1 position, representing 60 to 80% of the total 1-O-alkyl-2-acyl-glycero-3-phosphocholine. Thus, these results not only indicate a high degree of selectivity for utilization of precursor substrates for PAF biosynthesis, but also demonstrate that the selectivity is species specific.
通过气相色谱-负离子化学电离质谱法，研究了未刺激的以及经钙离子载体（A23187）刺激的大鼠、小鼠和豚鼠中性粒细胞（PMN）以及大鼠嗜碱性白血病（RBL）细胞合成的血小板活化因子（PAF）的分子异质性。在所有研究的细胞中均检测到了几种碳链长度从C14:0到C19:0的PAF分子种类。每种细胞类型产生的PAF呈现出独特的分子种类分布模式。虽然C16:0是大鼠PMN和RBL细胞中主要的PAF分子种类，分别占总PAF的96%和85%，但小鼠PMN产生的PAF中C16:0占81%，C18:1占10%，C18:0占6%。另外，经A23187刺激的豚鼠PMN产生的PAF分子种类中，C16:0占35%，C17:0占35%，C18:1占8%，C18:0占3%。还观察到静息细胞和经离子载体刺激的细胞在PAF分子种类分布上存在微小但显著的差异。与PAF分子种类组成不同，所有细胞类型的前体1-O-烷基-2-酰基甘油-3-磷酸胆碱在sn-1位主要是十六烷基（C16:0）烷基链，占总1-O-烷基-2-酰基甘油-3-磷酸胆碱的60%至80%。因此，这些结果不仅表明PAF生物合成中前体底物利用具有高度选择性，还证明这种选择性具有物种特异性。
