Table 1. Ventricular trabeculae:... | Rockefeller University Press

Table 1.

Ventricular trabeculae: Steady-state twitch contractions and [Ca²⁺]_i transients

Mechanical/calcium parameters	Control	Detubulated	Control	Detubulated
	1 Hz		3 Hz
Active stress (mN/mm²)	24.3 ± 5.3	20.3 ± 3.5^a	37.9 ± 7.1	23.9 ± 2.5^b
Passive stress (mN/mm²)	2.6 ± 0.8	1.3 ± 0.9^b	3.3 ± 0.9	2.4 ± 1.0^a
Twitch time to peak (ms)	96 ± 3	131 ± 4^b	83 ± 3	119 ± 5^b
Twitch relaxation time 50% (ms)	101 ± 7	119 ± 8^a	92 ± 5	107 ± 10^a
Twitch relaxation time 90% (ms)	197 ± 14	227 ± 15^a	163 ± 8	177 ± 6^b
Ca²⁺ transients (Δ ratio F₃₄₀/F₃₈₀)	0.68 ± 0.06	0.55 ± 0.03^a	0.78 ± 0.06	0.59 ± 0.03^a
Diastolic [Ca²⁺]_i (ratio F₃₄₀/F₃₈₀)	0.59 ± 0.02	0.54 ± 0.03^a	0.64 ± 0.03	0.57 ± 0.03^a
[Ca²⁺]_i time to peak (ms)	36 ± 2	58 ± 3^a	30 ± 2	52 ± 2^a
[Ca²⁺]_i decay time 50% (ms)	144 ± 7	157 ± 7^a	121 ± 3	127 ± 3^a
[Ca²⁺]_i decay time 90% (ms)	247 ± 9	273 ± 10^a	205 ± 4	226 ± 4^a

Mechanical/calcium parameters	Control	Detubulated	Control	Detubulated
	1 Hz		3 Hz
Active stress (mN/mm²)	24.3 ± 5.3	20.3 ± 3.5^a	37.9 ± 7.1	23.9 ± 2.5^b
Passive stress (mN/mm²)	2.6 ± 0.8	1.3 ± 0.9^b	3.3 ± 0.9	2.4 ± 1.0^a
Twitch time to peak (ms)	96 ± 3	131 ± 4^b	83 ± 3	119 ± 5^b
Twitch relaxation time 50% (ms)	101 ± 7	119 ± 8^a	92 ± 5	107 ± 10^a
Twitch relaxation time 90% (ms)	197 ± 14	227 ± 15^a	163 ± 8	177 ± 6^b
Ca²⁺ transients (Δ ratio F₃₄₀/F₃₈₀)	0.68 ± 0.06	0.55 ± 0.03^a	0.78 ± 0.06	0.59 ± 0.03^a
Diastolic [Ca²⁺]_i (ratio F₃₄₀/F₃₈₀)	0.59 ± 0.02	0.54 ± 0.03^a	0.64 ± 0.03	0.57 ± 0.03^a
[Ca²⁺]_i time to peak (ms)	36 ± 2	58 ± 3^a	30 ± 2	52 ± 2^a
[Ca²⁺]_i decay time 50% (ms)	144 ± 7	157 ± 7^a	121 ± 3	127 ± 3^a
[Ca²⁺]_i decay time 90% (ms)	247 ± 9	273 ± 10^a	205 ± 4	226 ± 4^a

Twitch force and Ca²⁺ transient amplitude and kinetics before and after formamide shock. The time to 50 and 90% relaxation/decay is measured from the peak of the twitch. Temperature was 30°C. Extracellular calcium ([Ca²⁺]_e) was 1.5 mM for force measurements (n = 15 and n = 20) and 1 mM for Ca²⁺ transient measurements (n = 7 and 13, number of rats and number of trabeculae, respectively). At 1 mM [Ca²⁺]_e (1 Hz), tension was 17.4 ± 2.9 before and 12.2 ± 2.9 after detubulation. P < 0.05; contraction kinetics were similar to those at 1.5 mM [Ca²⁺]_e.

P < 0.05 in paired Student t test.

P < 0.01 in paired Student t test.

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