Figure 3 of
Zhang, Mol Vis 2001;
Figure 3. Ca2+ effect on RA inhibition of HGJ channel currents
A: An outward HGJ channel current was gradually induced by external Ca2+ concentration switch from 2 mM to 0 mM at a holding potential of 30 mV in an H-2 type horizontal cell. 0.3 mM RA alone produced a 249 pA reduction from 762 pA to 513 pA. After washout, 100 mM Ca2+ produced a 222 pA inhibition. Coapplication of 100 mM Ca2+ and 0.3 mM at-RA only produced 272 pA inhibition. Each point represents the mean current from a 1.3 s interval of recording. B: Normalized dose inhibition relationships for RA on HGJ channel currents in the absence and presence of 100 mM Ca2+. Each point is an average from 4 to 6 cells and smooth curves were fitted with the Hill equation. Ca2+ decreased the apparent RA affinity for HGJ channel current, increasing the IC50 from 0.44 mM to 1.1 mM without affecting maximal inhibition.