Figure 9. Stimulation of Na/K pump current in the presence of physiological (10 mM) cytoplasmic Na and in the absence of cytoplasmic K.
To evoke significant Ca influx in the presence of low cytoplasmic Na, FPL64176 was employed to lock L-type Ca channels open at 0 mV. On application of 6 mM extracellular Ca, inward Ca current amounted several hundred pA, and current inactivated with a time constant of about 1 s. Thereafter, Cm increased by 3%, similar to results with reverse Na/Ca exchange, and peak and 12 s pump currents were roughly doubled. Similar results were obtained in 4 similar experiments.