title: Generation of superoxide radicals by human peripheral neutrophils activated by chemotactic factor. Evidence for the role of calcium.
abstract: In response to activation by the synthetic chemotactic factor FMLP, human peripheral neutrophils generated superoxide radicals as assessed by ferricytochrome C reduction. A dose-dependent increase in the amount of superoxide induced by FMLP over the concentration range of 1 X 10(-8) M to 1.6 X 10(-7) M was observed. Examination of the kinetics of the response revealed large amounts of superoxide generated by 1 min of incubation at 37 degrees C at an optimal dose of FMLP and a plateau effect after 5 min of incubation. Divalent cations did not influence the binding of 3H-FMLP to the cell, but superoxide generation by FMLP-activated neutrophils was observed to be dependent on the presence of divalent cations in the medium. In the absence of Mg2+, increasing Ca2+ ion concentration in the medium led to progressive increases in superoxide generation up to 4 mM, after which the response declined slightly. Mg2+, 0.25 to 4 mM, increased FMLP-induced superoxide generation to a much lower extent than did Ca2+. Lanthanum ion, 0.1 to 1 mM, in the presence of 1 mM Ca2+ inhibited the production of superoxide by FMLP 4 X 10(-8 ) M. Over the concentration range 3.3 X 10(-5 M to 3 X 10(-4 M, verapamil, a drug which selectively blocks the calcium channel, caused a dose-dependent inhibition of superoxide production and calcium-45 uptake in response to FMLP. This effect of verapamil could be overcome by increasing the concentration of Ca2+ in the medium. These observations suggest that a calcium influx plays an important role in the superoxide-generating capacity of the neutrophil.
mesh_terms: D002118:Calcium / Q000502:physiology*; D002634:Chemotaxis, Leukocyte; D006801:Humans; D007811:Lanthanum / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D009504:Neutrophils / Q000502:physiology; D010100:Oxygen / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism*
chemical_list: D013481:Superoxides; D007811:Lanthanum; D008274:Magnesium; D010100:Oxygen; D002118:Calcium