Am J Physiol Regul Integr Comp Physiol 285: R132-R142, 2003.
First published March 6, 2003; doi:10.1152/ajpregu.00196.2002
0363-6119/03 $5.00
INFLAMMATION, CYTOKINES, AND TEMPERATURE REGULATION
Ca2+ uptake and cellular integrity in rat EDL muscle exposed to electrostimulation, electroporation, or A23187
Hanne Gissel and
Torben Clausen
Department of Physiology, University of Aarhus, DK-8000 Århus C, Denmark
Submitted 4 April 2002
; accepted in final form 5 March 2003
We tested the hypothesis that increased Ca2+ uptake in rat extensor digitorum longus (EDL) muscle elicits cell membrane damage as assessed from release of the intracellular enzyme lactate dehydrogenase (LDH). This was done by using 1) electrostimulation, 2)
electroporation, and 3) the Ca2+ ionophore A23187.
Stimulation at 1 Hz for 120–240 min caused an increase in
45Ca uptake that was closely correlated to LDH release. This LDH
release increased markedly with temperature. After 120 min of stimulation at 1
Hz, resting 45Ca uptake was increased 5.6-fold compared with
unstimulated muscles. This was associated with an eightfold increase in LDH
release, and this effect was halved by lowering extracellular Ca2+
concentration ([Ca2+]o). The poststimulatory increase in
resting 45Ca uptake persisted for at least 120 min. An acute
increase in sarcolemma leakiness induced by electroporation markedly increased
45Ca uptake and LDH leakage. Both effects depended on
[Ca2+]o. A23187 increased 45Ca uptake.
Concomitantly, LDH leakage increased 18-fold within 30 min, and this effect
was abolished by omitting Ca2+ from the buffer. We conclude that
increased Ca2+ influx may be an important cause of cell membrane
damage that arises during and after exercise or electrical shocks. Because
membrane damage allows further influx of Ca2+, this results in
positive feedback that may further increase membrane degeneration.
Ca2+-ionophore; skeletal; extensor digitorum longus; lactate dehydrogenase
Address for reprint requests and other correspondence: Hanne Gissel, Dept. of Physiology, Univ. of Aarhus, DK-8000 Århus C., Denmark (E-mail: hgh{at}fi.au.dk).
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Copyright © 2003 by the American Physiological Society.
