HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:
Guest Access | Sign In via User Name/Password

This Article Full Text Free Full Text (PDF) Free Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Add to My Personal Article Archive Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Blanc, F.-X. Articles by Lecarpentier, Y. Search for Related Content PubMed PubMed Citation Articles by Blanc, F.-X. Articles by Lecarpentier, Y.

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

^* 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{at}bct.ap-hop-paris.fr

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.

Key Words: airways • cardiac hypertrophy • force-velocity relationship • smooth muscle