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https://hdl.handle.net/2440/43295
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Type: | Journal article |
Title: | Comparison of the effects of inorganic phosphate on caffeine-induced Ca2+ release in fast- and slow-twitch mammalian skeletal muscle |
Author: | Posterino, Giuseppe Saverio Dunn, Stacey Leanne |
Citation: | American Journal of Physiology-Cell Physiology, 2007; 294:C97-C105 |
Publisher: | American Physiological Society |
Issue Date: | 2007 |
ISSN: | 0363-6143 |
School/Discipline: | School of Molecular and Biomedical Science |
Statement of Responsibility: | Giuseppe S. Posterino and Stacey L. Dunn |
Abstract: | We compared the effects of 50 mM Pi on caffeine-induced Ca2+ release in mechanically skinned fast-twitch (FT) and slow-twitch (ST) skeletal muscle fibers of the rat. The time integral (area) of the caffeine response was reduced by 57% (FT) and 27% (ST) after 30 s of exposure to 50 mM Pi in either the presence or absence of creatine phosphate (to buffer ADP). Differences in the sarcoplasmic reticulum (SR) Ca2+ content between FT and ST fibers [40% vs. 100% SR Ca2+ content (pCa 6.7), respectively] did not contribute to the different effects of Pi observed; underloading the SR of ST fibers so that the SR Ca2+ content approximated that of FT fibers resulted in an even smaller (21%), but not significant, reduction in caffeine-induced Ca2+ release by Pi. These observed differences between FT and ST fibers could arise from fiber-type differences in the ability of the SR to accumulate Ca2+-Pi precipitate. To test this, fibers were Ca2+ loaded in the presence of 50 mM Pi. In FT fibers, the maximum SR Ca2+ content (pCa 6.7) was subsequently increased by up to 13 times of that achieved when loading for 2 min in the absence of Pi. In ST fibers, the SR Ca2+ content was only doubled. These data show that Ca2+ release in ST fibers was less affected by Pi than FT fibers, and this may be due to a reduced capacity of ST SR to accumulate Ca2+-Pi precipitate. This may account, in part, for the fatigue-resistant nature of ST fibers. |
Keywords: | fatigue; Ca2+ precipitation; excitation-contraction coupling |
Description: | Copyright © 2008 by the American Physiological Society. |
DOI: | 10.1152/ajpcell.00155.2007 |
Appears in Collections: | Molecular and Biomedical Science publications |
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