Mutation S652L shows higher isradipine sensitivity. Concentration–response curves for WTL and S652LL steady-state ICa inhibition by isradipine. Data are presented as mean ± SEM for the n-numbers indicated. Curves were fitted using a Hill slope = 1 and top-bottom fixed (bottom = 0; top = 100). IC50 values are given as means with 95% confidence interval. The statistical significance was determined using the extra sum-of-squares F test (p < 0.0001).