Cardiac β-adrenergic inotropic reserve was not further compromised post-MI in TgGRK5 compared to NLC mice, suggesting that GRK5, unlike GRK2,4 is not interfering with β-AR downregulation and perhaps only the mutant form of GRK5 affects β-ARs in HF setting.29 This evidence concerns the gene CTBP1 and myocardial infarction.