Levosimendan improves calcium sensitivity of diaphragm muscle fibres from a rat model of heart failure

BACKGROUND AND PURPOSE Diaphragm muscle weakness occurs in patients with heart failure (HF) and is associated with exercise intolerance and increased mortality. Reduced sensitivity of diaphragm fibres to calcium contributes to diaphragm weakness in HF. Here we have investigated the ability of the ca...

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Bibliographic Details
Published in:	British journal of pharmacology Vol. 162; no. 3; pp. 566 - 573
Main Authors:	van Hees, HWH, Andrade Acuña, GL, Linkels, M, Dekhuijzen, PNR, Heunks, LMA
Format:	Journal Article
Language:	English
Published:	Oxford, UK Blackwell Publishing Ltd 01-02-2011 Nature Publishing Group
Subjects:	Animal models Animals Anti-Arrhythmia Agents - pharmacology Biological and medical sciences Calcium Calcium - pharmacology calcium sensitization Cardiac muscle Cardiology. Vascular system coronary artery Diaphragm Diaphragm - drug effects Diaphragm - physiology Heart Heart diseases heart failure Heart Failure - physiopathology Heart failure, cardiogenic pulmonary edema, cardiac enlargement Humans Hydrazones - pharmacology Intolerance Male Medical sciences Mortality Muscle contraction Muscle Contraction - drug effects Muscle Fibers, Skeletal - chemistry Muscle Fibers, Skeletal - drug effects Muscle Fibers, Skeletal - physiology Muscle Weakness Muscles Myosin Heavy Chains - analysis Pharmacology. Drug treatments Physical training Pyridazines - pharmacology Rats Rats, Wistar Research Papers respiratory muscle Skin skinned fibres Heart failure Animal model Cardiotonic agent Calcium Rat Rodentia skinned fibres Cardiovascular disease Respiratory system Inorganic element Vertebrata Sensitivity Mammalia Respiratory muscle calcium sensitization Levosimendan Heart disease Sensitization Diaphragm
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Summary:	BACKGROUND AND PURPOSE Diaphragm muscle weakness occurs in patients with heart failure (HF) and is associated with exercise intolerance and increased mortality. Reduced sensitivity of diaphragm fibres to calcium contributes to diaphragm weakness in HF. Here we have investigated the ability of the calcium sensitizer levosimendan to restore the reduced calcium sensitivity of diaphragm fibres from rats with HF. EXPERIMENTAL APPROACH Coronary artery ligation in rats was used as an animal model for HF. Sham‐operated rats served as controls. Fifteen weeks after induction of HF or sham operations animals were killed and muscle fibres were isolated from the diaphragm. Diaphragm fibres were skinned and activated with solutions containing incremental calcium concentrations and 10 µM levosimendan or vehicle (0.02% DMSO). Developed force was measured at each calcium concentration, and force–calcium concentration relationships were plotted. KEY RESULTS Calcium sensitivity of force generation was reduced in diaphragm muscle fibres from HF rats, compared with fibres from control rats (P < 0.01). Maximal force generation was ∼25% lower in HF diaphragm fibres than in control fibres (P < 0.05). Levosimendan significantly increased calcium sensitivity of force generation in diaphragm fibres from HF and control rats, without affecting maximal force generation. CONCLUSIONS AND IMPLICATIONS Levosimendan enhanced the force generating capacity of diaphragm fibres from HF rats by increasing the sensitivity of force generation to calcium concentration. These results provide strong support for testing the effect of calcium sensitizers on diaphragm muscle weakness in patients with HF.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2
ISSN:	0007-1188 1476-5381 1476-5381
DOI:	10.1111/j.1476-5381.2010.01048.x