Complement-induced Ca2+ influx in cultured fibroblasts is decreased by the calcium-channel antagonist nifedipine or by some bivalent inorganic cations.
The effects of different extracellular cations or organic Ca(2+)-channel modulators on complement-induced changes in intracellular Ca2+ and cell death have been investigated in the transfected NIH-3T3 HIR 3.5 cell line, which overexpresses the human insulin receptor. Cells were incubated with mouse anti-(human insulin receptor) monoclonal antibodies before exposure to rabbit or human serum (sources of heterologous complement). Changes in intracellular Ca2+ were complement-dependent (measured by influx of 45Ca), as was cytotoxicity (monitored by leakage of lactate dehydrogenase into the culture supernatant). Addition of a dihydropyridine Ca(2+)-channel antagonist (nifedipine) or some bivalent inorganic cations caused inhibition of 45Ca entry via a novel channel distinct from endogenous voltage-gated Ca2+ channels. Nifedipine decreased, but conversely the addition of a phenylalkylamine Ca(2+)-channel antagonist (verapamil) or the inorganic Ca2+ agonists Ba2+ and Sr+ increased, complement-induced cytotoxicity. These agents had no effect on cell viability at the studied concentrations, in the absence of complement. It is concluded that complement-induced cytotoxicity is mediated by Ca2+ influx through novel specific transmembrane channels which are sensitive to the Ca(2+)-channel antagonist nifedipine, but otherwise show little resemblance to L- or T-type voltage-gated Ca2+ channels.
Newsholme
P
P
Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, U.K.
Adogu
A A
AA
Soos
M A
MA
Hales
C N
CN
D016475:3T3 Cells / Q000378:metabolism; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002413:Cations, Divalent; D003171:Complement Pathway, Classical; D003165:Complement System Proteins / Q000494:pharmacology*; D004533:Egtazic Acid / Q000494:pharmacology; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D015636:Magnesium Chloride / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology*; D051379:Mice; D009543:Nifedipine / Q000494:pharmacology*; D013324:Strontium / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology*
D002121:Calcium Channel Blockers; D002413:Cations, Divalent; D015636:Magnesium Chloride; D001464:Barium; D008345:Manganese; D004533:Egtazic Acid; D003165:Complement System Proteins; D014700:Verapamil; D007770:L-Lactate Dehydrogenase; D009543:Nifedipine; D015032:Zinc; D002118:Calcium; D013324:Strontium