Figure 5.
Effect of UCL-2077 on IK(DR) in GH3 cells. In these experiments, we bathed cells in Ca2+-free Tyrode’s solution, which contained 1 μM TTX to suppress Na+ current, and backfilled the pipette with K+-containing solution. (A) Representative IK(DR) traces elicited by step depolarization (indicated in the upper part) were obtained in the absence (a) and presence of 3 (b), 10 (c), or 30 μM (d) UCL-2077. (B) Concentration-response curve for UCL-2077-induced inhibition of IK(DR) in these cells. The peak amplitude of IK(DR) measured at the end of depolarizing voltage step during exposure to UCL-2077 was compared with the control value (mean ± SEM, n = 8 for each point). The smooth line represents the best fit to the modified Hill equation (equation (1)). The values for IC50, the Hill coefficient, and maximally inhibited percentage of IK(DR) were 13.4 μM, 1.1, and 55%, respectively.