Perchlorate differentially potentiates excitation-contraction coupling of diaphragm muscle from mdx and control mice.
The effects of perchlorate (6-40 mM) on contractile properties and depolarization-contraction coupling of diaphragm have been tested in muscle fibre bundles from 8 to 12-week-old mdx and control mice. Twitch contractile properties were affected by perchlorate to a similar extent in mdx and control muscles. In the absence of perchlorate, voltage-dependent parameters of both activation and inactivation were similar in mdx and control muscles. In both mdx and control muscles, perchlorate induced a shift of activation and inactivation curves toward more negative potentials. However, mdx diaphragm fibres were less sensitive to perchlorate in the low range of concentrations (6-12 mM). These results are unlikely to be due to a possible effect of the lack of dystrophin on the excitation-contraction coupling voltage sensor or ryanodine receptor. However, necrosis and regeneration occur in mdx mouse diaphragm and it is postulated that the presence of a high proportion of not fully mature fibres could contribute to the reduced sensitivity of mdx diaphragm fibres to perchlorate.
Péréon
Y
Y
Laboratoire de Physiopathologie et Pharmacologie Cellulaire et Moléculaire, Hópital G.R. Laënnec, Nantes, France.
Khammari
A
A
Noireaud
J
J
D000818:Animals; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D003964:Diaphragm / Q000187:drug effects* / Q000503:physiopathology*; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D018101:Mice, Inbred mdx; D009119:Muscle Contraction / Q000187:drug effects*; D009124:Muscle Proteins / Q000187:drug effects / Q000502:physiology; D009137:Muscular Dystrophy, Animal / Q000235:genetics / Q000503:physiopathology*; D010472:Perchlorates / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel; D017670:Sodium Compounds / Q000494:pharmacology*
D015220:Calcium Channels; D009124:Muscle Proteins; D010472:Perchlorates; D019837:Ryanodine Receptor Calcium Release Channel; D017670:Sodium Compounds; C031068:sodium perchlorate; D011188:Potassium