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 Posted: Fri Oct 03, 2008 8:59 pm Post subject: Sarcoplasmic reticulum Ca2+ release declines in muscle fiber |
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Biophys J. 2008 Apr 15;94(8):3178-88. Epub 2008 Jan 4. Links
Sarcoplasmic reticulum Ca2+ release declines in muscle fibers from
aging mice.Jiménez-Moreno R, Wang ZM, Gerring RC, Delbono O.
Department of Physiology and Pharmacology, Wake Forest University
School of Medicine, Winston-Salem, North Carolina 27157, USA.
This study hypothesized that decline in sarcoplasmic reticulum (SR)
Ca(2+) release and maximal SR-releasable Ca(2+) contributes to
decreased specific force with aging. To test it, we recorded
electrically evoked maximal isometric specific force followed by 4-
chloro-m-cresol (4-CmC)-evoked maximal contracture force in single
intact fibers from the mouse flexor digitorum brevis muscle.
Significant differences in tetanic, but not in 4-CmC-evoked,
contracture forces were recorded in fibers from aging mice as compared
to younger mice. Peak intracellular Ca(2+) in response to 4-CmC did
not differ significantly. SR Ca(2+) release was recorded in whole-cell
patch-clamped fibers in the linescan mode of confocal microscopy using
a low-affinity Ca(2+) indicator (Oregon green bapta-5N) with high-
intracellular ethylene glycol-bis(alpha-aminoethyl ether)-N,N,N>N'-
tetraacetic acid (20 mM). Maximal SR Ca(2+) release, but not voltage
dependence, was significantly changed in fibers from old compared to
young mice. Increasing the duration of fiber depolarization did not
increase the maximal rate of SR Ca(2+) release in fibers from old
compared to young mice. Voltage-dependent inactivation of SR Ca(2+)
release did not differ significantly between fibers from young and old
mice. These findings indicate that alterations in excitation-
contraction coupling, but not in maximal SR-releasable Ca(2+), account
for the age-dependent decline in intracellular Ca(2+) mobilization and
specific force.
PMID: 18178643 [PubMed - indexed for MEDLINE]
PMCID: PMC2275691 [Available on 04/15/09] |
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