title: Effect of saturated and unsaturated fatty acids on the oxidative metabolism of human neutrophils. The role of calcium ion in the extracellular medium.
abstract: The ability of fatty acids to stimulate the generation of superoxide anion (O2-) by human neutrophils was investigated with respect to their Krafft points. Saturated (myristic acid) and unsaturated (elaidic and oleic acid) induced a marked O2- generation and release from human neutrophils at pH 7.4 in the absence of Ca2+, while 0.3 mM Ca2+ inhibited both myristic acid and elaidic acid-induced O2- release. [14C]Myristic acid association with neutrophils was reduced by addition of Ca2+, whereas oleic acid association was not affected. When the pH of the reaction mixture was lowered to 6.4, 0.6 mM Ca2+ did not inhibit the O2- generation by human neutrophils. These results indicate that the inhibitory effect of Ca2+ on the fatty acid-induced O2- generation might be due to the ionic interaction between the carboxyl group of the fatty acid and Ca2+. Furthermore, 11-methyltridecanoic acid, a branched isomer of myristic acid, which showed the low Krafft point even in the presence of Ca2+, stimulated O2- generation by human neutrophils not only in the absence but also in the presence of 0.6 mM Ca2+. The effect of Ca2+ on the fatty acid-induced O2- generation by neutrophils was discussed with reference to its possible relationship to the Krafft point.
mesh_terms: D002118:Calcium / Q000494:pharmacology*; D002478:Cells, Cultured; D005227:Fatty Acids / Q000494:pharmacology*; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013481:Superoxides / Q000378:metabolism*
chemical_list: D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D013481:Superoxides; D002118:Calcium