Contractile properties of myocardium are altered in dystrophin-deficient mdx mice

The objective of this study was to determine whether cardiac contractile force is altered in the dystrophin-deficient mdx mouse model of muscular dystrophy. Left atria from 12-14-week-old control and mdx mice were paced at 1 Hz in 1.25 mM external Ca2+ buffer. Twitch properties and effects of interp...

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Bibliographic Details
Published in:Journal of the neurological sciences 1996-10, Vol.142 (1-2), p.17-24
Main Authors: SAPP, J. L, BOBET, J, HOWLETT, S. E
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Calcium - metabolism
Diseases of striated muscles. Neuromuscular diseases
Dystrophin - genetics
Female
Heart - physiology
Medical sciences
Mice
Mice, Inbred C57BL
Mice, Inbred mdx - physiology
Muscle Contraction - physiology
Muscle Fibers, Skeletal - physiology
Mutation - physiology
Myocardium - chemistry
Myocardium - metabolism
Neurology
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Summary:The objective of this study was to determine whether cardiac contractile force is altered in the dystrophin-deficient mdx mouse model of muscular dystrophy. Left atria from 12-14-week-old control and mdx mice were paced at 1 Hz in 1.25 mM external Ca2+ buffer. Twitch properties and effects of interposing intervals of 0.3 to 600 s on the force of subsequent beats (force-interval curves) were examined. Peak force and time-to-peak force were similar in both groups, but half-relaxation time was significantly prolonged in mdx heart. In control hearts, force-interval curves increased to an inflection point at about 1 s, then rose to a second peak near 60 s. In mdx heart, curves reached the early inflection more quickly, the second peak was diminished in magnitude and force was greatly depressed at long intervals. Curves were fitted to a four-parameter equation to quantify differences in shape. The parameter a, which reflects rate of rise to the first inflection, was significantly increased in mdx atria, while the parameter B, which reflects amplitude of the late peak, was significantly reduced. These differences in force production were more marked when external Ca2+ was raised to 2.5 mM. Results show contractile properties are markedly altered in atria from dystrophin-deficient mdx mice. These findings are consistent with the hypothesis that dystrophin deficiency affects cardiac contractile function, possibly through effects on SR function.
ISSN:0022-510X
1878-5883
DOI:10.1016/0022-510x(96)00167-0