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Gravin (AKAP12) is an A-kinase-anchoring-protein that scaffolds protein kinase A (PKA), β₂-adrenergic receptor (β₂-AR), protein phosphatase 2B and protein kinase C. Gravin facilitates β₂-AR-dependent signal transduction through PKA to modulate cardiac excitation-contraction coupling and its removal positively affects cardiac contraction. Trabeculae from the right ventricles of gravin mutant (gravin-t/t) mice were employed for force determination. Simultaneously, corresponding intracellular Ca²⁺ transient ([Ca²⁺]_i) were measured. Twitch force (T_f)-interval relationship, [Ca²⁺]_i-interval relationship, and the rate of decay of post-extrasysolic potentiation (R_f) were also obtained. Western blot analysis were performed to correlate sarcomeric protein expression with alterations in calcium cycling between the WT and gravin-t/t hearts. Gravin-t/t muscles had similar developed force compared to WT muscles despite having …