Characteristics of Store-Operated Ca(superscript 2+)-Permeable Current in Monocytic U937 Cells

Sheng-Nan Wu；Chung-Ren Jan；Hui-Fan Li

monocyte ； store-operated Ca(superscript 2+)-permeable channel ； nifedipine

The Chinese Journal of Physiology

40卷3期（1997 / 09 / 01）

115 - 120

英文

The electrophysiological properties of store-operated Ca(superscript 2+)-permeable current in monocytic U937 cell line were characterized. The whole-cell voltage clamp technique with patch pipette containing Cs-internal solution was carried out. Membrane currents were elicited by the ramp pulses from -90mV to +40mV with a duration of 200msec. After the presence of Ca(superscript 2+)-free Tyrode's solution plus cyclopiazonic acid (30μM), A23187 (10μM) or ATP (30μM) in cells for 10 minutes, a significant inward current was markedly elicited by further application of CaC12 (2mM). This net inward current was reversed at about -12mV with inward rectification. The reversal potential of this current was not significantly altered by the replacement of intracellular Cl(superscript -) concentrations. The activation of this current is thus referred to as be store-operated Ca(superscript 2+)-permeable current (I(superscript SOC)). The addition of LaCl3(100μM) or NiCl2 (100μM) markedly blocked I(superscript SOC). The replacement of NaCl with N-methyl-D-glucamine chloride decreased the amplitude of this current at the level of -80mV by 50%. Nifedipine (3-100μM) effectively suppressed the amplitude of I(superscript SOC) in a concentration-dependent manner. The EC50 value for nifedipine-induced inhibition of I(superscript SOC) is 10μM. However, verapamil (30μM) or Bay K 8644 (30μM) did not produce any effect on it. The present studies indicate that in monocytic U937 cells, Ca(superscript 2+) entry elicited by store depletion is mediated through store-operated Ca(superscript 2+)-permeable channel which is responsive to nifedipine.