title: Is intracellular Ca2+ the trigger for oxygen radical production by polymorphonuclear leucocytes?
abstract: The aim of this paper is critically to evaluate the existing evidence for the role of intracellular Ca2+ in polymorphonuclear leucocyte (PMN) activation and in particular in oxygen radical production. Indirect experiments are based on the manipulation of extracellular Ca2+, measurement of 45Ca fluxes, employing pharmacological agents such as Ca2+-ionophores and intracellular Ca2+ antagonists and monitoring chlortetracycline fluorescence. Experiments of this type do not provide the necessary definitive evidence that an increase in intracellular Ca2+ is the trigger for PMN activation. Recent direct measurements of intracellular free Ca2+ using the Ca2+-activated photoprotein, obelin, and the Ca2+-sensitive fluorescent indicator, quin 2, have provided evidence for the existence of two distinct mechanisms of activation, one triggered by a rise in intracellular Ca2+ and the other independent of a rise in intracellular Ca2+. The source of the Ca2+ for the former mechanism is mainly extracellular but can also come from an intracellular Ca2+ store.
mesh_terms: D000634:Aminoquinolines; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers; D002132:Calcium Radioisotopes; D002751:Chlortetracycline / Q000494:pharmacology; D005456:Fluorescent Dyes; D005609:Free Radicals; D006651:Histocytochemistry; D006801:Humans; D007476:Ionophores; D008164:Luminescent Proteins / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D000634:Aminoquinolines; D002121:Calcium Channel Blockers; D002132:Calcium Radioisotopes; D005456:Fluorescent Dyes; D005609:Free Radicals; D007476:Ionophores; D008164:Luminescent Proteins; C010497:obelin; C035739:Quin2; D010100:Oxygen; D002118:Calcium; D002751:Chlortetracycline