TY - JOUR T1 - Diaphragm function in experimental pulmonary hypertension JF - European Respiratory Journal JO - Eur Respir J VL - 38 IS - Suppl 55 SP - p2303 AU - Emmy Manders AU - Nico Westerhof AU - Anton Vonk-Noordegraaf AU - Frances de Man AU - Coen Ottenheijm Y1 - 2011/09/01 UR - http://erj.ersjournals.com/content/38/Suppl_55/p2303.abstract N2 - Introduction: Recently it was suggested that patients with pulmonary hypertension (PH) suffer from diaphragm dysfunction due to increased loading conditions. In the present study the aim is to determine the contractile strength of the diaphragm muscle in PH and control rats. The extensor digitorum longus (EDL) muscle will serve as a control skeletal muscle.Methods: PH was induced in Wistar rats by a single injection of monocrotaline (60 mg/kg). The diaphragm and EDL (PH n=5; controls n=5) muscle were excised for determination of in vitro contractile properties. Muscle bundles were treated with a relaxing solution (5°C) containing 1% Triton X-100 to permeabilize membranes. Single fibers were mounted on a single fiber apparatus. Maximum force (Fmax), rate constant of force redevelopment (Ktr), as a measure of the cross bridge kinetics, and calcium sensitivity (pCa50) were measured in diaphragm and EDL single muscle fibers.Results: In the EDL muscle no significant differences were found in Fmax and pCa50. Ktr was significantly higher in PH fibers: 10.86±0.79 vs 15.09±0.74 (p=0.005). The cross sectional area (CSA) of the fibers measured was significantly decreased in PH fibers: 2563±166.7 vs 1961±88.82 μm2 (p=0.013)Preliminary data on the diaphragm muscle (n=2), suggest a decrease of Fmax, Ktr, pCa50 and CSA. Fmax: 128.6±4.48 vs 105.5±7.03 mN/mm2, Ktr: 8.995±1.39 vs 7.601±0.56, pCa50: 5.780±0.069 vs 5.720±0.058, CSA: 2929±162 vs 1700±130 μm2.Conclusions: These data suggest a more pronounced effect of PH on the diaphragm muscle compared to EDL. However, more experiments on the diaphragm muscle and fiber type determination is necessary before final conclusions can be drawn. ER -