Figure 1. Effects of removal of extracellular Ca²⁺ and various related compounds on I_K in normal human oral keratinocytes. Cells were bathed in normal Tyrode’s solution containing 1.8 mM CaCl₂. (A) Superimposed current tracings obtained in the absence and presence of external CaCl₂. The cell was held at –40 mV, and the depolarizing pulses from –30 to +70 mV were delivered in 20-mV increments. The pipette solution contained 0.1 mM EGTA. The superimposed current traces shown in Aa are control, and those in Ab were obtained 2 min after cells were exposed to Ca²⁺-free solution containing 1 mM EGTA. (B) The current-voltage relations of outward currents in the presence and absence of extracellular Ca²⁺ concentration. • : 1.8 mM Ca²⁺; : Ca²⁺-free. Mean ± SEM (n = 6–8). (C) Bar graph showing the effects of various blockers of K⁺ channels on the relative amplitude of I_K in normal human oral keratinocytes. In these experiments, cells were bathed in normal Tyrode’s solution containing 1.8 mM CaCl₂, and the depolarizing pulses from –40 to +50 mV were applied. Current amplitude in the control was considered to be 1.0, and the relative amplitudes in the presence of each agent were compared. Pax, paxilline (1 µM); Iber, iberitoxin (200 nM); TEA, tetraethylammonium chloride (10 mM); Apa, apamin (200 nM); 5HD, 5-hydroxydecanoate sodium (10 µM); and Anan, anandamide (10 µM). The number of cells from which the data were taken is shown above the bars. Mean ± SEM. *Significantly different from the control group.