Extrajunctional resting Ca2+ influx is not increased in a severely dystrophic expiratory muscle (triangularis sterni) of the mdx mouse.
Freshly isolated adult mdx and nondystrophic (C57B110SnJ) muscle fibers were used to examine the potential role of resting Ca2+ influx in the pathogenesis of Duchenne and related dystrophies. Microfluorimetric determinations of resting divalent cation influx were obtained from undissociated intact muscle fibers in the triangularis sterni (TS), a thin expiratory muscle. Morphological evidence indicated severe dystrophic alterations in the mdx TS at 5 months, and a pronounced loss of fibers with connective tissue infiltration in older animals. To examine resting Ca2+ influx, fibers were loaded with FURA PE3 and the rate of quenching of intracellular signal following the extracellular addition of Mn2+ was determined from extrajunctional regions. There was no significant difference in quench rate between nondystrophic and mdx TS fibers. These results indicate that severe dystrophic pathology in the absence of dystrophin is not due to generalized increases in resting Ca2+ influx.
Carlson
C George
CG
Department of Physiology, Kirksville College of Osteopathic Medicine, Kirksville, MO 63501, USA. ccarlson@kcom.edu
Gueorguiev
Anton
A
Roshek
Diana M
DM
Ashmore
Rebecca
R
Chu
Jacquelyne S
JS
Anderson
Judy E
JE
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D066298:In Vitro Techniques; D051379:Mice; D018101:Mice, Inbred mdx; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D009136:Muscular Dystrophies / Q000235:genetics / Q000378:metabolism*; D009469:Neuromuscular Junction / Q000378:metabolism*
D015220:Calcium Channels; D002118:Calcium