Figure 5. Normalized force-pCa relationships in Tnnt2 ^{+/ −}/TG^WT and Tnnt2 ^{+/ −}/TG^K210Δ skinned papillary muscle fibers.

Normalized force (i.e., ratio of force at a given pCa and maximally activated force at pCa = 4.33) developed at a range of Ca²⁺ concentrations was assessed at sarcomere lengths 1.9 µm (Tnnt2 ^+/−/TG^WT •, Tnnt2 ^+/−/TG^K210Δ ▪) and 2.3 µm (Tnnt2 ^+/−/TG^WT ○, Tnnt2 ^+/−/TG^K210Δ □). There was a rightward shift of the force-pCa curve in Tnnt2 ^+/−/TG^K210Δ muscle, indicating Ca²⁺ desensitization. Values are mean±SE (n = 10 for Tnnt2 ^+/−/TG^WT and n = 7 for Tnnt2 ^+/−/TG^K210Δ).