Table 2. Characteristics of slow-twitch... | Rockefeller University Press

Table 2.

Characteristics of slow-twitch skeletal muscle fibers before and after 12 h of exchange with WT or pseudo-phosphorylated cTnI

Exchange	WT		S22/23DD		Y26E		S22/23DD + Y26E
Exchange	Before	After	Before	After	Before	After	Before	After
n	5		5		7		5
Fiber length (µm)	1,103 ± 58		809 ± 60		1,030 ± 72		1,156 ± 132
Fiber width (µm)	77 ± 9		68 ± 8		67 ± 4		68 ± 6
Resting sarcomere length (µm)	2.52 ± 0.02		2.49 ± 0.05		2.51 ± 0.02		2.44 ± 0.03
Active sarcomere length (µm)	2.34 ± 0.05		2.35 ± 0.04		2.39 ± 0.03		2.35 ± 0.03
Passive force (µN)	2.75 ± 0.89	1.67 ± 0.33	1.86 ± 0.39	0.98 ± 0.27	2.03 ± 0.48	1.33 ± 0.30	2.45 ± 0.82	2.45 ± 1.02
Passive tension (kN/m²)	0.65 ± 0.17	0.41 ± 0.07	0.60 ± 0.15	0.28 ± 0.03	0.62 ± 0.10	0.44 ± 0.10	0.83 ± 0.12	0.66 ± 0.16
Max force (µN)	569 ± 66	450 ± 74^{^a}	380 ± 57	308 ± 49^{^a}	439 ± 52	320 ± 50^{^a}	404 ± 86	354 ± 81^{^a}
Max tension (kN/m²)	127 ± 19	103 ± 20^{^a}	119 ± 14	95 ± 10^{^a}	137 ± 10	95 ± 7^{^a}	120 ± 17	105 ± 18^{^a}
k_tr @ pCa 4.5 (s⁻¹)	4.30 ± 0.34	3.21 ± 0.19^{^a}	5.10 ± 0.28	3.83 ± 0.26	4.75 ± 0.31	3.11 ± 0.27	4.83 ± 0.28	3.63 ± 0.26^{^a}
pCa for half-maximal force	6.28 ± 0.04	6.28 ± 0.04	6.26 ± 0.05	6.10 ± 0.03	6.31 ± 0.01	6.09 ± 0.03^{^a}	6.26 ± 0.04	6.08 ± 0.04
Relative force (P_O/P_4.5)	0.47 ± 0.01	0.45 ± 0.02	0.47 ± 0.03	0.42 ± 0.02	0.48 ± 0.03	0.51 ± 0.02	0.45 ± 0.02	0.47 ± 0.04
Power output (µW/mg)	2.60 ± 0.45	1.76 ± 0.31^{^a}	2.24 ± 0.34	1.83 ± 0.19	2.36 ± 0.26	2.02 ± 0.16	2.15 ± 0.29	2.27 ± 0.31
a/P_O	0.10 ± 0.02	0.06 ± 0.01	0.10 ± 0.01	0.08 ± 0.02^{^a}	0.11 ± 0.03	0.07 ± 0.01	0.11 ± 0.03	0.09 ± 0.01
F_opt (P/P_O)	0.23 ± 0.01	0.19 ± 0.01^{^a}	0.23 ± 0.01	0.21 ± 0.02	0.22 ± 0.02	0.19 ± 0.02	0.23 ± 0.02	0.22 ± 0.01
V_opt (ML/s)	0.14 ± 0.01	0.16 ± 0.01	0.15 ± 0.01	0.19 ± 0.03	0.14 ± 0.01	0.20 ± 0.03^{^a}	0.16 ± 0.01	0.19 ± 0.01^{^a}
V_max	0.62 ± 0.05	0.82 ± 0.04^{^a}	0.64 ± 0.08	1.01 ± 0.26	0.66 ± 0.10	1.21 ± 0.28	0.70 ± 0.11	0.85 ± 0.09
PNPO (P/P_O*ML/s)	0.032 ± 0.004	0.033 ± 0.003	0.033 ± 0.002	0.039 ± 0.002^{^a}	0.030 ± 0.002	0.036 ± 0.002^{^a}	0.036 ± 0.002	0.042 ± 0.003^{^a}^,^{^b}
Submax k_tr	1.22 ± 0.14	1.40 ± 0.22	1.05 ± 0.26	1.10 ± 0.18	0.98 ± 0.12	1.31 ± 0.10^{^a}	1.36 ± 0.24	1.37 ± 0.14

Exchange	WT		S22/23DD		Y26E		S22/23DD + Y26E
Exchange	Before	After	Before	After	Before	After	Before	After
n	5		5		7		5
Fiber length (µm)	1,103 ± 58		809 ± 60		1,030 ± 72		1,156 ± 132
Fiber width (µm)	77 ± 9		68 ± 8		67 ± 4		68 ± 6
Resting sarcomere length (µm)	2.52 ± 0.02		2.49 ± 0.05		2.51 ± 0.02		2.44 ± 0.03
Active sarcomere length (µm)	2.34 ± 0.05		2.35 ± 0.04		2.39 ± 0.03		2.35 ± 0.03
Passive force (µN)	2.75 ± 0.89	1.67 ± 0.33	1.86 ± 0.39	0.98 ± 0.27	2.03 ± 0.48	1.33 ± 0.30	2.45 ± 0.82	2.45 ± 1.02
Passive tension (kN/m²)	0.65 ± 0.17	0.41 ± 0.07	0.60 ± 0.15	0.28 ± 0.03	0.62 ± 0.10	0.44 ± 0.10	0.83 ± 0.12	0.66 ± 0.16
Max force (µN)	569 ± 66	450 ± 74^{^a}	380 ± 57	308 ± 49^{^a}	439 ± 52	320 ± 50^{^a}	404 ± 86	354 ± 81^{^a}
Max tension (kN/m²)	127 ± 19	103 ± 20^{^a}	119 ± 14	95 ± 10^{^a}	137 ± 10	95 ± 7^{^a}	120 ± 17	105 ± 18^{^a}
k_tr @ pCa 4.5 (s⁻¹)	4.30 ± 0.34	3.21 ± 0.19^{^a}	5.10 ± 0.28	3.83 ± 0.26	4.75 ± 0.31	3.11 ± 0.27	4.83 ± 0.28	3.63 ± 0.26^{^a}
pCa for half-maximal force	6.28 ± 0.04	6.28 ± 0.04	6.26 ± 0.05	6.10 ± 0.03	6.31 ± 0.01	6.09 ± 0.03^{^a}	6.26 ± 0.04	6.08 ± 0.04
Relative force (P_O/P_4.5)	0.47 ± 0.01	0.45 ± 0.02	0.47 ± 0.03	0.42 ± 0.02	0.48 ± 0.03	0.51 ± 0.02	0.45 ± 0.02	0.47 ± 0.04
Power output (µW/mg)	2.60 ± 0.45	1.76 ± 0.31^{^a}	2.24 ± 0.34	1.83 ± 0.19	2.36 ± 0.26	2.02 ± 0.16	2.15 ± 0.29	2.27 ± 0.31
a/P_O	0.10 ± 0.02	0.06 ± 0.01	0.10 ± 0.01	0.08 ± 0.02^{^a}	0.11 ± 0.03	0.07 ± 0.01	0.11 ± 0.03	0.09 ± 0.01
F_opt (P/P_O)	0.23 ± 0.01	0.19 ± 0.01^{^a}	0.23 ± 0.01	0.21 ± 0.02	0.22 ± 0.02	0.19 ± 0.02	0.23 ± 0.02	0.22 ± 0.01
V_opt (ML/s)	0.14 ± 0.01	0.16 ± 0.01	0.15 ± 0.01	0.19 ± 0.03	0.14 ± 0.01	0.20 ± 0.03^{^a}	0.16 ± 0.01	0.19 ± 0.01^{^a}
V_max	0.62 ± 0.05	0.82 ± 0.04^{^a}	0.64 ± 0.08	1.01 ± 0.26	0.66 ± 0.10	1.21 ± 0.28	0.70 ± 0.11	0.85 ± 0.09
PNPO (P/P_O*ML/s)	0.032 ± 0.004	0.033 ± 0.003	0.033 ± 0.002	0.039 ± 0.002^{^a}	0.030 ± 0.002	0.036 ± 0.002^{^a}	0.036 ± 0.002	0.042 ± 0.003^{^a}^,^{^b}
Submax k_tr	1.22 ± 0.14	1.40 ± 0.22	1.05 ± 0.26	1.10 ± 0.18	0.98 ± 0.12	1.31 ± 0.10^{^a}	1.36 ± 0.24	1.37 ± 0.14

Mechanical properties were tested before and after recombinant cTn exchange and compared via two-way repeated measures ANOVA. Values are mean ± SEM.

P ≤ 0.05 vs. before same group.

P ≤ 0.05 vs. WT group. n equals the number of slow-twitch skeletal muscle fibers (biological replicates).

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