Am. J. Respir. Crit. Care Med., Volume 162, Number 1, July 2000, 278-281

Severe Mechanical Dysfunction in Pharyngeal Muscle from Adult mdx Mice

PIERRE ATTAL, FRANCINE LAMBERT, SYLVAIN MARCHAND-ADAM, SERGE BOBIN, JEAN-CLAUDE POURNY, DENIS CHEMLA, YVES LECARPENTIER, and CATHERINE COIRAULT

Service d'Oto-Rhyno-Laryngologie et de Chirurgie Cervico-Faciale, Hôpital de Bicêtre; INSERM U451-Loa-ENSTA-Ecole Polytechnique, Palaiseau Cedex; and Service de Physiologie Cardio-vasculaire et Respiratoire, UER Paris XI, Hôpital de Bicêtre, Assistance Publique-Hôpitaux de Paris, Le Kremlin-Bicêtre, France

The mdx mouse is a widely used animal model of human muscular dystrophy. Although diaphragm muscle exhibits severe muscle weakness throughout the life of the animal, the limb muscle function of mdx mice spontaneously recovers by 6 mo of age. Pharyngeal dilator muscles such as sternohyoid (SH) contribute to upper airway patency during breathing. We hypothesized that SH muscle function was impaired in 6-mo-old mdx mice. Mechanical properties and myosin heavy chain (MHC) composition were investigated in isolated SH from 6-mo-old control (C, n = 10) and mdx (n = 10) mice. As compared with C, peak tetanic tension (Pmax) and maximum shortening velocity were 50% and 16% lower in mdx mice (p < 0.001 and p < 0.05, respectively). Peak mechanical power was lower in mdx than in C (19.0 ± 3.2 versus 57.4 ± 5.1 mW g¹, p < 0.001). Both C and mdx SH were composed exclusively of fast myosin isoforms. As compared with C, mdx SH presented a higher proportion of IIX-MHC and a reduction in IIB-MHC (each p < 0.001). In conclusion, our results demonstrated severe SH muscle dysfunction in 6-mo-old mdx mice, that is, at a time when limb muscle function has recovered. Thus, SH muscle of the mdx mouse may be an excellent muscle for studying Duchenne muscular dystrophy.

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