Nom du corpus

Corpus Systématique Animale

Titre du document

Contractile and calcium regulating capacities of myocardia of different sized mammals scale with resting heart rate

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Springer (journals)
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Type de document
Mots-clés d'auteur
  • myosin
  • myofibrillar
  • sarcoplasmic reticulum
  • ATPase activity
  • biochemical scaling
Nom du fichier dans la ressource
  • N. Hamilton 1
  • C. D. Ianuzzo 1
  • 1) Departments of Physical Education and Biology, York University, M3J 1P3, Toronto, ON, Canada

The purpose of this study was to determine if selected biochemical parameters representing the contractile and calcium regulating systems of cardiac muscle scaled among mammals having inherently different resting heart rates (RHR). Eight mammalian species with RHR ranging from 51 to 475 beats per minute (bpm) were studied. The oxidative capacity of the myocardium is highly correlated with the RHR. The hypothesis of the present study was that the capacities of the energy utilizing processes of contraction and calcium regulation would also be correlated to the functional demand imposed on the muscle as represented by the RHR. Myosin (M) and myofibrillar (MF) ATPase activities, myosin isoenzyme distribution and sarcoplasmic reticulum (SR) ATPase activity were determined. Animals with RHR above 300 bpm express V1 myosin while animals with lower RHR express primarily V3. M and MF ATPase activities correlated with RHR, but the major difference in activities occurred at the ‘threshold’ RHR of about 300 bpm at which the switch from V3 to V1 appears to occur. SR ATPase activity per mg of microsomal protein was for the most part constant among different mammals, but the SR ATPase activity per g of heart tissue was significantly correlated with RHR as slower beating hearts tended to yield less SR protein per unit mass. We conclude that both the contractile and calcium regulating systems are scaled to the functional parameter of RHR among different mammals. The contractile system uses a slow myosin ATPase isoform at low resting heart rates whereas above the postulated threshold RHR of about 300 bpm a switch in gene expression to a fast myosin ATPase isoform occurs. For the calcium regulating system, the heart does not seem to have the ‘choice’ of altering the quality of the SR ATPase isoform and thus calcium regulating capacity is set by alterations in the quantity of SR per unit of heart mass.

Catégories Science-Metrix
  • 1 - health sciences
  • 2 - biomedical research
  • 3 - biochemistry & molecular biology
Catégories INIST
  • 1 - sciences appliquees, technologies et medecines
  • 2 - sciences biologiques et medicales
  • 3 - sciences medicales
Catégories Scopus
  • 1 - Life Sciences ; 2 - Biochemistry, Genetics and Molecular Biology ; 3 - Cell Biology
  • 1 - Life Sciences ; 2 - Biochemistry, Genetics and Molecular Biology ; 3 - Clinical Biochemistry
  • 1 - Life Sciences ; 2 - Biochemistry, Genetics and Molecular Biology ; 3 - Molecular Biology
  • 1 - Health Sciences ; 2 - Medicine ; 3 - General Medicine
Catégories WoS
  • 1 - science ; 2 - cell biology
Identifiant ISTEX

Molecular and Cellular Biochemistry

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  • Mammiferes
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