title: Counteracting effects of NADPH oxidase and the Na+/Ca2+ exchanger on membrane repolarisation and store-operated uptake of Ca2+ by chemoattractant-activated human neutrophils.
abstract: This study was designed to investigate the possible involvement of NADPH oxidase and the Na(+)/Ca(2+) exchanger in regulating membrane repolarisation and store-operated uptake of Ca(2+) by FMLP (1 microM)-activated human neutrophils. Diphenyleneiodonium chloride (DPI, 5-10 microM) and KB-R7943 (2.5-10 microM), inhibitors of NADPH oxidase and the reverse mode of the Na(+)/Ca(2+) exchanger respectively, were used as pharmacological probes. Transmembrane fluxes of Ca(2+), K(+) and Na(+) were determined radiometrically, while alterations in membrane potential and cytosolic Ca(2+) were evaluated using spectrofluorimetric procedures. DPI, added to the cells at the time of maximum FMLP-activated membrane depolarisation, accelerated the rates of both membrane repolarisation and influx of Ca(2+), while KB-R7943 effectively antagonised these processes. SKF 96365 (10 microM), an antagonist of store-operated Ca(2+) channels, abolished the influx of Ca(2+) into FMLP-activated neutrophils, but had no effects on membrane repolarisation, suggesting that the Na(+)/Ca(2+) exchanger is primarily involved in mediating membrane repolarisation, thereby facilitating uptake of Ca(2+) via store-operated channels. These observations are compatible with prominent negative and positive regulatory roles for NADPH oxidase and the Na(+)/Ca(2+) exchanger respectively in regulating the rates of membrane repolarisation and store-operated uptake of Ca(2+) by chemoattractant-activated neutrophils.
authors.affiliation: Medical Research Council Unit for Inflammation and Immunity, Department of Immunology, Institute of Pathology, University of Pretoria, Pretoria, South Africa.
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Tintinger
authors.forename: Ronald
authors.initials: R
authors.lastname: Anderson
mesh_terms: D002118:Calcium / Q000378:metabolism; D002630:Chemotactic Factors / Q000494:pharmacology*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D019255:NADPH Oxidases / Q000378:metabolism*; D018375:Neutrophil Activation / Q000187:drug effects*; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D009861:Onium Compounds / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism; D013890:Thiourea / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: C101670:2-(2-(4-(4-nitrobenzyloxy)phenyl)ethyl)isothiourea methanesulfonate; D002630:Chemotactic Factors; D007093:Imidazoles; D009861:Onium Compounds; D019831:Sodium-Calcium Exchanger; D013481:Superoxides; D009240:N-Formylmethionine Leucyl-Phenylalanine; C007517:diphenyleneiodonium; D012964:Sodium; D019255:NADPH Oxidases; D013890:Thiourea; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D011188:Potassium; D002118:Calcium