Role of reactive oxygen species and Ca2+ dissociation from the myofilaments in determination of Ca2+ wave propagation in rat cardiac muscle

Effect of myofilament Ca2+ sensitivity on Ca2+ wave propagation in rat ventricular muscle

“…85-23, revised in 1996) and were approved by the Ethics Review Board of Tohoku University (approval reference number: 21-98). Briefly, after the rats had been adequately anesthetized, trabeculae (n = 60; length: 2.6 ± 0.3 mm; width: 281 ± 73 μm; thickness: 83 ± 3 μm in a slack condition) were dissected from the endocardial region of the rat right ventricle and mounted on an inverted microscope between a force transducer and a micromanipulator in a bath superfused with HEPES solution containing 5 mM KCl, as previously described [13][14][15]21,23,25]. Force was measured using a silicon strain gauge, sarcomere length (SL) using laser diffraction techniques, and [Ca 2+ ] i using fura-2, as previously described [23].…”

“…ROS production was estimated using 2′,7′-dichlorofluorescein (DCF) fluorescence from the muscle, as previously described [15]. Briefly, a trabecula was loaded with 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA) [28].…”

“…Recently, it has been reported that muscle stretch increases the frequency of Ca 2+ sparks [16,17] due to production of reactive oxygen species (ROS) by the activation of NADPH oxidase in cardiac muscle [18]. In addition, we have reported that in rat cardiac muscle, muscle stretch increases 2′,7′-dichlorofluorescein (DCF) fluorescence, which may reflect ROS production, and increases the velocity of Ca 2+ waves initiated from the region under Ca 2+ overload [15]. In that study, however, it was unclear whether ROS production was involved in the increase in the propagation velocity of Ca 2+ waves.…”

“…Muscle stretch increases myofilament Ca 2+ sensitivity and increases Ca 2+ binding to the myofilaments [12], thereby increasing the developed force [13][14][15]. Recently, it has been reported that muscle stretch increases the frequency of Ca 2+ sparks [16,17] due to production of reactive oxygen species (ROS) by the activation of NADPH oxidase in cardiac muscle [18].…”

“…Ca 2+ waves are initiated not only by Ca 2+ leak from the sarcoplasmic reticulum (SR) under Ca 2+ overload [20] but also by Ca 2+ dissociation from the myofilaments under nonuniform contraction [15,21]. These waves propagate along the cardiac muscle by the mechanism of Ca 2+ -induced Ca 2+ release from the SR [22,23] although it has been reported in other studies that such waves may be driven intermittently by both calcium and membrane depolarization [24].…”