Sustained Release of Calcium Elicited by Membrane Depolarization in Ryanodine-Injected Mouse Skeletal Muscle Fibers - INRAE - Institut national de recherche pour l’agriculture, l’alimentation et l’environnement Access content directly
Journal Articles Biophysical Journal Year : 2002

Sustained Release of Calcium Elicited by Membrane Depolarization in Ryanodine-Injected Mouse Skeletal Muscle Fibers

Abstract

The effect of micromolar intracellular levels of ryanodine was tested on the myoplasmic free calcium concentration ([Ca2+](i)) measured from a portion of isolated mouse skeletal muscle fibers voltage-clamped at -80 mV. When ryanodine-injected fibers were transiently depolarized to 0 mV, the early decay phase of [Ca2+](i) upon membrane repolarization was followed by a steady elevated [Ca2+](i) level. This effect could be qualitatively well simulated, assuming that ryanodine binds to release channels that open during depolarization and that ryanodine-bound channels do not close upon repolarization. The amplitude of the postpulse [Ca2+](i) elevation depended on the duration of the depolarization, being hardly detectable for pulses shorter than 100 ms, and very prominent for duration pulses of seconds. Within a series of consecutive pulses of the same duration, the effect of ryanodine produced a staircase increase in resting [Ca2+](i), the slope of which was approximately twice larger for depolarizations to 0 or + 10 mV than to -30 or -20 mV. Overall results are consistent with the "open-locked" state because of ryanodine binding to calcium release channels that open during depolarization. Within the voltage-sensitive range of calcium release, increasing either the amplitude or the duration of the depolarization seems to enhance the fraction of release channels accessible to ryanodine.

Dates and versions

hal-03534712 , version 1 (19-01-2022)

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Claude Collet, Vincent Jacquemond. Sustained Release of Calcium Elicited by Membrane Depolarization in Ryanodine-Injected Mouse Skeletal Muscle Fibers. Biophysical Journal, 2002, 82 (3), pp.1509-1523. ⟨10.1016/S0006-3495(02)75504-5⟩. ⟨hal-03534712⟩
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