FIGURE 6.

Quantification of β-adrenergic receptor and selected Ca²⁺-handling proteins from young (6 months) and old (15 months) WT and R21C heart homogenates. Expression of proteins relative to GAPDH was quantified by immunoblot analyses. The amount of each protein in R21C (gray) mouse heart homogenates was normalized to the WT (black) mean values. A, comparison of β1-AR, CSQ, NCX1, and SERCA2a expression. B, comparison of phosphorylated phospholamban (PLB^Ser-16 and PLB^Ser-17), total phospholamban (PLB), and phosphorylated MyBP-C^Ser-282. Data are given as mean ± S.E. (n = 3–4 hearts/genotype and age group). *, p < 0.05; †, p < 0.01 versus WT. Error bars, S.E.