Changes in membrane potential during calcium ion influx and efflux across the mitochondrial membrane

Biochim Biophys Acta. 1978 May 10;502(2):359-66. doi: 10.1016/0005-2728(78)90056-7.

Abstract

1. A depolarisation of the membrane of rat liver mitochondria, as measured with the safranine method, is seen during Ca2+ uptake. The depolarisation is followed by a slow repolarisation, the rate of which can be increased by the addition of EGTA or phosphate. 2. Plots relating the initial rate of calcium ion (Ca2+) uptake and the decrease in membrane potential (delta psi) to the Ca2+ concentration show a half-maximal change at less than 10 micron Ca2+ and a saturation above 20 micron Ca2+. 3. Plots relating the initial rate of Ca2+ uptake to delta psi are linear. 4. Addition of Ca2+ chelators, nitriloacetate or EGTA, to deenergized mitochondria equilibrated with Ca2+ causes a polarisation of the mitochondrial membrane due to a diffusion potential created by electrogenic Ca2+ efflux. 5. If the extent of the response induced by different nitriloacetate concentrations is plotted against the expected membrane potential a linear plot is obtained up to 70 mV with a slope corresponding to two-times the extent of the response induced by valinomycin in the presence of different potassium ion gradients. This suggests that the Ca2+ ion is transferred across the membrane with one net positive charge in present conditions.

MeSH terms

  • Acetates / pharmacology
  • Animals
  • Biological Transport, Active
  • Calcium / metabolism*
  • Diffusion
  • Egtazic Acid / pharmacology
  • Kinetics
  • Male
  • Membrane Potentials / drug effects
  • Mitochondria, Liver / metabolism*
  • Rats

Substances

  • Acetates
  • Egtazic Acid
  • Calcium