A and B, Western blot analysis of Cx43 protein expression. Cell lysates (10 μg) from primary cardiac muscle cells were treated for 30 minutes without (A) or with the indicated agents (5μM compound II [iSK], 10μM GW9846, 6.5μM THI, or 1μM S1P) (B) and then with RLX (50 ng/mL) for 24 hours. Quantification of band intensity, shown in the graphic, is reported as ratio between overall Cx43/β-actin, and relative to control normalized to 100. Data are mean ± SEM (n = 3, Student's t test; *, P < .05 vs untreated cells (vehicle); §, P < .05 vs RLX).