Mechanical properties of rat cardiac skinned fibers are altered by chronic growth hormone hypersecretion.

Détails

ID Serval
serval:BIB_30D0D83AF6E0
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Institution
Titre
Mechanical properties of rat cardiac skinned fibers are altered by chronic growth hormone hypersecretion.
Périodique
Circulation Research
Auteur(s)
Mayoux E., Ventura-Clapier R., Timsit J., Béhar-Cohen F., Hoffmann C., Mercadier J.J.
ISSN
0009-7330 (Print)
ISSN-L
0009-7330
Statut éditorial
Publié
Date de publication
1993
Peer-reviewed
Oui
Volume
72
Numéro
1
Pages
57-64
Langue
anglais
Notes
Publication types: Comparative Study ; Journal Article ; Research Support, Non-U.S. Gov'tPublication Status: ppublish
Résumé
Chronic growth hormone (GH) hypersecretion in rats leads to increased isometric force without affecting the unloaded shortening velocity of isolated cardiac papillary muscles, despite a marked isomyosin shift toward V3. To determine if alterations occurred at the level of the contractile proteins in rats bearing a GH-secreting tumor (GH rats), we examined the mechanical properties of skinned fibers to eliminate the early steps of the excitation-contraction coupling mechanism. We found that maximal active tension and stiffness at saturating calcium concentrations (pCa 4.5) were markedly higher in GH rats than in control rats (tension, 52.9 +/- 5.2 versus 38.1 +/- 4.6 mN.mm-2, p < 0.05; stiffness, 1,105 +/- 120 versus 685 +/- 88 mN.mm-2.microns-1, p < 0.01), whereas values at low calcium concentrations (pCa 9) were unchanged. In addition, the calcium sensitivity of the contractile proteins was slightly but significantly higher in GH rats than in control rats (delta pCa 0.04, p < 0.001). The crossbridge cycling rate, reflected by the response to quick length changes, was lower in GH rats than in control rats (62.0 +/- 2.6 versus 77.4 +/- 6.6 sec-1, p < 0.05), in good agreement with a decrease in the proportion of alpha-myosin heavy chains in the corresponding papillary muscles (45.5 +/- 2.0% versus 94.6 +/- 2.4%, p < 0.001). The changes in myosin heavy chain protein phenotype were paralleled by similar changes of the corresponding mRNAs, indicating that the latter occurred mainly at a pretranslational level. These results demonstrate that during chronic GH hypersecretion in rats, alterations at the myofibrillar level contribute to the increase in myocardial contractility observed in intact muscle.
Mots-clé
Animals, Calcium/metabolism, Cell Line/secretion, Female, Growth Hormone/pharmacology, Growth Hormone/secretion, Heart/drug effects, Heart/physiology, Isometric Contraction/drug effects, Myocardial Contraction/drug effects, Myocardium/metabolism, Myosins/analysis, Myosins/drug effects, RNA, Messenger/analysis, Rats, Rats, Inbred Strains
Pubmed
Web of science
Création de la notice
10/04/2014 14:43
Dernière modification de la notice
20/08/2019 14:15
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