The Na+‐independent Ca2+ efflux system in mitochondria is a Ca2+/2H+ exchange system

Abstract
The mechanism of the Na + -independent Ca 2+ efflux system in mitochondria has not been elucidated as yet. With the aid of cyclosporin A. an inhibitor of the Ca 2+ -induced ‘pore’, and using a variety of inhibitors, uncouplers and lonophores, it is possible to demonstrate, unequivocally, that this process is driven by ΔpH. The efflux is not affected by ΔΨ, thus suggesting an electroneutral Ca 2+ /2H + exchange mechanism. Parallel measurements of the rate of Ca 2+ efflux and ΔpH, as modulated by valinomycin and nigericin, indicate that the rate of efflux is a function of the magnitude of ΔpH.