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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 
 
 

Biochemical, mechanical and energetic characterization of right ventricular hypertrophy in the ferret heart.

Ferret right ventricular hypertrophy is characterized by a decreased and prolonged isometric contraction, associated with altered intracellular calcium (Ca2+) regulation. However myofibrillar composition, cross-bridge function and/or energy transfer may also be involved in these contractile disturbances. Therefore, mechanical properties of myofibrils have been studied with Triton X-100-skinned fibres and troponin (Tn) T and I composition has been examined. Mitochondrial function and functional activity of creatine kinase (CK) isoforms have been studied in saponin-skinned fibres of control ( C) and hypertrophied (H) ferret right ventricle, to check for a possible mismatch between energy production and utilization. Our results show that neither TnT nor TnI isoform expression, nor myofibrillar Ca2+ responsiveness (similar apparent Ca2+ sensitivity and Hill coefficient) were affected by pressure-overload. Similarly, maximal tension and stiffness, as well as cross-bridge cycling rate (v)--assessed by quick length changes--were not significantly altered. Importantly, passive stiffness was dramatically increased (163 +/- 30 mN/mm2/microns for C v 500 +/- 121 mN/mm2/microns for H; P < 0.02). Moreover, there was a significant correlation between passive stiffness and cross-bridge cycling rate, indicating that a factor involved in the passive stiffness may affect cross-bridge kinetics. Oxidative capacity (normalized to ventricular dry weight), reflecting mitochondrial ATP production and mitochondrial CK efficacy, as well as myofibrillar CK efficacy (assessed by the shift of MgATP-rigor tension curves before and after phosphocreatine addition), were similar in both groups. These results demonstrate that ferret right ventricular pressure-overload was accompanied by a development of myofibrils and a parallel increase of energy production capacity, transfer and utilization. Decreased compliance, probably linked to an increase in the collagen fraction and/or alterations of the cytoskeletal architecture of the overloaded ventricle, could contribute to the slower time course and decreased amplitude of the isometric twitch.[1]

References

  1. Biochemical, mechanical and energetic characterization of right ventricular hypertrophy in the ferret heart. Baudet, S., Kuznetsov, A., Merciai, N., Gorza, L., Ventura-Clapier, R. J. Mol. Cell. Cardiol. (1994) [Pubmed]
 
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