[The effect of the external electric field on Ca2+ transport in the sarcoplasmic reticulum]

The effect of active and passive Ca2+ transport in sarcoplasmic reticulum vesicles on the rate of negative diffusion potential dissipation was investigated by the method of potential-sensitive fluorescent probes. Membrane potentials were generated by K+ gradients in the presence of valinomycin and were measured using dye diS-C3-(5). It was shown that the rate of K+ potential dissipation was accelerated during Ca2+ transport and depended on ATP and Ca2+ concentrations. In its turn the initial rate of ATP hydrolysis was found to be increased in the presence of negative potential. The obtained results support an electrogenic mechanism for the Ca2+ transport by the sarcoplasmic reticulum.