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Fig. 6. The fast Cl^- currents show Ca²⁺ dependence. (A) Representative voltage clamp records of currents (elicited from eight +20 mV step increases, beginning from -57 mV) from a cell in a zero Ca²⁺ bath solution (shadow, a representative trace from a different cell in ASW at +63 mV). Open arrowhead, position of fast I-V; filled arrowhead, position of slow I-V. (Bi) Slow I-V reveals the cells in the 0 Ca²⁺ bath (open squares, N=5) have reduced currents as compared to those in normal ASW (filled circles, N=76), but are larger than the currents in a Low Cl^- bath (open triangles, N=18). Smaller still are currents from cells in a Low Cl^-, 0 Ca²⁺ bath (open diamonds, N=10). (Bii) Comparison of maximum current amplitude between ASW (at 73 mV, N=76), 0 Ca²⁺ (73 mV, N=5), Low Cl^- (70 mV, N=18), and Low Cl^-, 0 Ca²⁺ (70 mV, N=10) reveal each treatment results in significantly smaller current amplitude when compared to the ASW control (P=8.7x10^-15). (Ci) Fast I-V reveals an even larger difference in current amplitude between ASW (filled circles, N=76), and the 0 Ca²⁺ bath (open squares, N=5), which remains slightly larger than the currents in a Low Cl^- bath (open triangles, N=18). (Cii) Comparison of maximum current shows an even larger discrepancy in amplitude between ASW (at 73 mV, N=76) and 0 Ca²⁺ bath (73 mV, N=5) and Low Cl^- (70 mV, N=18) (P=3.4x10^-11). (D) Currents from one cell depolarized to 63 mV before and after the addition of 2 mmol l^-1 Cd²⁺ to the bath. (E) Currents from one cell depolarized to 63 mV before and after the addition of the Ca²⁺ channel blocker nifedipine (Nif; 50 µmol l^-1). (F) Means for the total current reduction after exposure to either nifedipine or Cd²⁺. Both the Cd²⁺ reduction (N=7, P=0.01) and the nifedipine reduction (N=5, P=1.9x10^-5) are significant.

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