Cardiomyopathy-Related Mutations in Cardiac Troponin C, L29Q and G159D, Have Divergent Effects on Rat Cardiac Myofiber Contractile Dynamics

Figure 4

Comparison of normalized pCa-tension relationships in detergent-skinned fibers reconstituted with cTnC_WT, cTnC_L29Q, or cTnC_G159D. Isometric steady-state tensions elicited by each fiber in various pCa solutions were normalized with its respective value in pCa 4.3 solution. The normalized tensions were plotted against pCa to construct the pCa-tension relationship. The Hill equation was fitted to the normalized pCa-tension relationships to estimate myofilament Ca²⁺ sensitivity (pCa₅₀) and the Hill coefficient (𝑛_H). 𝑝𝐶𝑎₅₀ and 𝑛_H values are shown in Figures 5(a) and 5(b), respectively. The curves presented here are Hill fits to pCa-tension relationships in cTnC_WT (○), cTnC_L29Q (□), and cTnC_G159D (∆) fibers, respectively. Values are expressed as mean ± SEM. Number of fibers tested in each group is as follows: cTnC_WT,𝑛=15;cTnC_L29Q,𝑛=10;cTnC_G159D,𝑛=14.