A role of H+ flux in active Ca2+ transport into sarcoplasmic reticulum vesicles. I. Effect of an artificially imposed H+ gradient on Ca2+ uptake.
To ascertain the function of H+ flux in active Ca2+ transport into sarcoplasmic reticulum vesicles, the effect of pH gradient on Ca2+ transport was examined. A transient H+ gradient (inside-acidic) was imposed on K+-loaded sarcoplasmic reticulum vesicles with the aid of K+-H+ exchange driven by nigericin. This proton gradient was dissipated rapidly and concomitantly with ATP-driven Ca2+ transport. Under these conditions, the initial rate of the Ca2+ uptake was increased about 1.5-fold. The stimulation of Ca2+ uptake was completely lost when the pH gradient was cancelled with an uncoupler plus membrane permeable cation before Ca2+ uptake. These results are interpreted in terms of H+ efflux coupled with Ca2+ transport.
D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008744:Methylamines / Q000378:metabolism; D009550:Nigericin / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D011522:Protons; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D014634:Valinomycin / Q000494:pharmacology
D008744:Methylamines; D011522:Protons; D014634:Valinomycin; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D006859:Hydrogen; C027451:methylamine; D009550:Nigericin; D011188:Potassium; D002118:Calcium