H2O2 modulates twitch tension and increases Po of Ca2+ release channel in frog skeletal muscle
Oba, T.; Koshita, M.; Yamaguchi, M.
American Journal of Physiology 271(3 Pt 1): C810-C818
1996
ISSN/ISBN: 0002-9513 PMID: 8843710 Document Number: 461795
The effect of H-2O-2 was examined to elucidate the basis of muscle injury after exercise. Exposure of single fibers to 1.5-6 mM H-2O-2 led to twitch potentiation followed by a marked decrease. Then, fibers contracted spontaneously. BAY K 8644 augmented twitch potentiation and slowed the decay of twitches. In 5 mM dithiothreitol (DTT), twitch potentiation and spontaneous contraction were not observed on H-2O-2 addition. Cytoplasmic application of 1.5-3 mM H-2O-2 to heavy sarcoplasmic reticulum (SR) vesicles incorporated into planar lipid bilayers increased the open probability of Ca-2+ release channels, an effect reversed by DTT. We investigated oxidation of sulfhydryl groups on proteins in SR membrane by H-2O-2 with N-(7-dimethylamino-4-methyl-3-coumarinyl)maleimide. Pretreatment of light and heavy SR membranes with 1.5 mM H-2O-2 exponentially increased fluorescence intensity. The time constant of the intensity increase was increased markedly only in heavy SR in solution containing 50 mu-M cytoplasmic Ca-2+, so Ca-2+ release was associated with protein oxidation by H-2O-2. Thus extracellular H-2O-2 probably acts by oxidizing sulfhydryls of proteins at two distinct sites: the dihydropyridine receptors, oxidation of which elicits potentiation and subsequent inhibition of twitches, and Ca-2+ release channels, whose oxidation elicits spontaneous contraction, resulting in muscle dysfunction.