Hypoxia-induced chemiluminescence in human leukocytes: the role of Ca2+.
Circumstantial evidence suggests that in vivo hypoxia can activate human leukocytes to release a host of mediators including oxygen free radicals. Endothelial cells have always been presumed to play an important role in hypoxia-induced leukocyte activation. The primary aim of this study was to determine whether acute exposure of whole blood to a hypoxic mixture could stimulate the production of oxygen free radicals in the absence of endothelial cells, and to determine the role of Ca2+ in this process. Freshly drawn whole blood was obtained by venepuncture from 30 healthy volunteers. Exposure of blood to 6% O2 in a purpose built environmental chamber for periods of 8, 10, 15, 30, and 45 min resulted in a significant increase in the production of oxygen free radicals. This response was significantly increased after a 10-min incubation with the Ca2+ ionophore (A23187), supporting the idea that the influx of extracellular Ca2+ is an important step in the process. Incubation of human leukocytes with verapamil (10 min) and subsequent exposure to hypoxia resulted in the significantly reduction in hypoxia-induced production of oxygen free radicals at 15 min and a paradoxical increase at 30- and 45-min exposures. The significance of the results is discussed.
Sanidas
Dimitrios
D
Department of Biomedical Science, School of Science and Environment Cox St., Coventry University, Cox St., CV1 5FB., Coventry, UK.
Garnham
Andrew
A
Mian
Rubina
R
D000293:Adolescent; D000328:Adult; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015687:Cell Hypoxia; D005260:Female; D005609:Free Radicals / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007476:Ionophores / Q000494:pharmacology; D007958:Leukocyte Count; D007962:Leukocytes / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D008163:Luminescent Measurements; D008165:Luminol / Q000494:pharmacology; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D013997:Time Factors; D014700:Verapamil / Q000494:pharmacology
D002121:Calcium Channel Blockers; D005609:Free Radicals; D007476:Ionophores; D000001:Calcimycin; D008165:Luminol; D014700:Verapamil; D010100:Oxygen; D002118:Calcium