H+-dependent efflux of Ca2+ from heart mitochondria.
A rapid loss of accumulated Ca2+ is produced by addition of H+ to isolated heart mitochondria. The H+-dependent Ca+ efflux requires that either (a) the NAD(P)H pool of the mitochondrion be oxidized, or (b) the endogenous adenine nucleotides be depleted. The loss of Ca2+ is accompanied by swelling and loss of endogenous Mg2+. The rate of H+-dependent Ca2+ efflux depends on the amount of Ca2+ and Pi taken up and the extent of the pH drop imposed. In the absence of ruthenium red the H+-induced Ca2+-efflux is partially offset by a spontaneous re-accumulation of released Ca2+. The H+-induced Ca2+ efflux is inhibited when the Pi transporter is blocked with N-ethylmaleimide, is strongly opposed by oligomycin and exogenous adenine nucleotides (particularly ADP), and inhibited by nupercaine. The H+-dependent Ca2+ efflux is decreased markedly when Na+ replaces the K+ of the suspending medium or when the exogenous K+/H+ exchanger nigericin is present. These results suggest that the H+-dependent loss of accumulated Ca2+ results from relatively nonspecific changes in membrane permeability and is not a reflection of a Ca2+/H+ exchange reaction.
D000227:Adenine Nucleotides / Q000378:metabolism; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008929:Mitochondria, Heart / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D009550:Nigericin / Q000494:pharmacology; D009840:Oligomycins / Q000494:pharmacology
D000227:Adenine Nucleotides; D009840:Oligomycins; D009249:NADP; D000244:Adenosine Diphosphate; D006859:Hydrogen; D009550:Nigericin; D002118:Calcium