Regulation of leukotriene biosynthesis in human polymorphonuclear leukocytes.
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.
Schatz-Munding
M
M
University of Konstanz, Faculty of Biology, FRG.
Ullrich
V
V
D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism; D016718:Arachidonic Acid / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004533:Egtazic Acid / Q000494:pharmacology; D005456:Fluorescent Dyes; D016257:Fura-2; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D007975:Leukotriene B4 / Q000096:biosynthesis* / Q000494:pharmacology; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D010972:Platelet Activating Factor / Q000494:pharmacology
D005456:Fluorescent Dyes; D010972:Platelet Activating Factor; D007975:Leukotriene B4; D016718:Arachidonic Acid; D004533:Egtazic Acid; D015759:Ionomycin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D001094:Arachidonate 5-Lipoxygenase; D010741:Phospholipases A; D054467:Phospholipases A2; D002118:Calcium; D016257:Fura-2