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Laboratory and Animal Investigations |

Mechanical Properties of Tracheal Smooth Muscle Are Impaired in the Rabbit With Experimental Cardiac Pressure Overload*

François-Xavier Blanc; Olivier Langeron; Catherine Coirault; Sergio Salmeron; Francine Lambert; Bruno Riou; Yves Lecarpentier
Author and Funding Information

*From the Institut National de la Santé et de la Recherche Médicale (INSERM), ENSTA, Ecole Polytechnique (Drs. Blanc, Coirault, and Lambert), Palaiseau; Département d’Anesthésie-Réanimation, Groupe Hospitalier Pitié-Salpétrière, Assistance Publique-Hôpitaux de Paris (Dr. Langeron), Paris; Service d’Explorations Fonctionnelles Cardiovasculaires et Respiratoires, Hôpital de Bicêtre, Assistance Publique-Hôpitaux de Paris (Dr. Lecarpentier), Le Kremlin Bicêtre; Service de Pneumologie, Fondation Hôpital Saint-Joseph (Dr. Salmeron), Paris; and Service d’Accueil des Urgences, Groupe Hospitalier Pitié-Salpétrière, Assistance Publique-Hôpitaux de Paris, Université Pierre et Marie Curie (Dr. Riou), Paris, France.

Correspondence to: François-Xavier Blanc, MD, Unité de Pneumologie, Service de Médecine Interne, Hôpital de Bicêtre, 78 rue du Général Leclerc, 94275 Le Kremlin-Bicêtre Cedex, France; e-mail: xavier.blanc@bct.ap-hop-paris.fr



Chest. 2004;125(1):236-242. doi:10.1378/chest.125.1.236
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Study objectives/design: Impaired function of striated and arterial smooth muscle is known to occur in humans and animals with various forms of cardiac diseases, but limited information is available on the mechanical behavior of airway smooth muscle. We tested the hypothesis that the baseline mechanical properties of tracheal smooth muscle (TSM) were impaired at an early stage of cardiac overload.

Animals: We used a model of cardiac hypertrophy induced by surgical abdominal aortic stenosis (AS) in adult rabbits. Twelve animals with AS and 8 sham-operated control rabbits were studied 12 weeks after surgery. In rabbits with AS, the heart weight/body weight ratio was higher than in control rabbits (2.36 ± 0.43 g/kg vs 1.98 ± 0.20 g/kg, p < 0.05) [mean ± SD], attesting to moderate cardiac hypertrophy. No clinical signs of congestive heart failure were observed.

Measurements: Isolated TSM strips were electrically stimulated at 37°C, 2.5 mM [Ca2+]0, against 8 to 10 load levels, from zero load to full isometry. Force-velocity relationship was elicited using the conventional afterloaded isotonic method.

Results: Peak isometric tension was lower in rabbits with AS than in control rabbits (25 ± 11 mN/mm2 vs 34 ± 14 mN/mm2, p < 0.05), whereas maximum unloaded shortening velocity, maximum extent of muscle shortening, and relaxation parameters did not differ between groups. The curvature of the force-velocity relationship (which reflects the myothermal economy of force generation) and peak mechanical efficiency were lower in rabbits with AS than in control rabbits.

Conclusions: These results indicate that the contraction of isolated rabbit TSM was less powerful and less economical in cardiac hypertrophy, attesting to early impairment of the mechanical properties of TSM during cardiac overload.

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