Schatz-Munding M, Ullrich V
University of Konstanz, Faculty of Biology, FRG.
Eicosanoids. 1992;5 Suppl:S35-6.
Since the formation of leukotrienes in human polymorphonuclear leukocytes is Ca-dependent we have determined the Ca-pools involved and the enzymes affected. With PAF, fMLP and LTB4 as agonists the Ca-transients measured with Fura-2 showed the same height of the intracellular Ca-signal but an external Ca-component in decreasing magnitude. In parallel the activity of 5-lipoxygenase was also decreasing. 5-lipoxygenase was linearly dependent on Ca with saturation of around 350 nMol/l already provided by the release of intracellular Ca. Phospholipase A2, however, started to activate at about this concentration. Hence arachidonate is a limiting factor in stimulated leukocytes due to a limited influx of extracellular Ca.
由于人类多形核白细胞中白三烯的形成依赖于钙，我们已经确定了所涉及的钙池以及受影响的酶。以血小板活化因子（PAF）、N-甲酰甲硫氨酸-亮氨酸-苯丙氨酸（fMLP）和白三烯B4（LTB4）作为激动剂，用Fura-2测量的钙瞬变显示细胞内钙信号的高度相同，但细胞外钙成分的幅度在减小。与此同时，5-脂氧合酶的活性也在下降。5-脂氧合酶线性依赖于钙，细胞内钙释放已经提供了约350 nMol/l的饱和浓度。然而，磷脂酶A2在大约这个浓度时开始激活。因此，由于细胞外钙的流入有限，花生四烯酸是刺激白细胞中的一个限制因素。
