Dynamic calcium requirements for activation of rabbit papillary muscle calculated from tension-independent heat
| Autor: | Louis A. Mulieri, Norman R. Alpert, E. M. Blanchard |
|---|---|
| Rok vydání: | 1990 |
| Předmět: |
medicine.medical_specialty
Hot Temperature chemistry.chemical_element Calcium-Transporting ATPases Calcium Creatine Troponin C chemistry.chemical_compound Adenosine Triphosphate Internal medicine medicine Animals Papillary muscle business.industry Papillary Muscles Phosphate Actin cytoskeleton Myocardial Contraction Electric Stimulation Actin Cytoskeleton Sarcoplasmic Reticulum medicine.anatomical_structure Endocrinology chemistry Cardiology Biophysics Rabbits Cardiology and Cardiovascular Medicine business Adenosine triphosphate |
| Zdroj: | The American journal of cardiology. 65(14) |
| ISSN: | 0002-9149 |
| Popis: | The heat generated by right ventricular papillary muscles of rabbits was measured after adenosine triphosphate (ATP) splitting by the contractile proteins was chemically inhibited. This tension-independent heat (TIH) (1 mJ/g wet weight) was used to calculate the total calcium (Ca) cycled in a muscle twitch by assuming that 87% of TIH was due to Ca2+ transport by the sarcoplasmic reticulum with a coupling ratio of 2 Ca2+/ATP split; the enthalpy of creatine phosphate hydrolysis buffering ATP was taken as -34 KJ/mol. The estimated Ca turnover per muscle twitch at 21 degrees C, 0.2 Hz pacing rate, and 2.5 mM Ca in the Krebs solution was approximately equal to 50 nmol/g wet weight. There was a tight positive correlation between TIH and mechanical activation during steady-state measurements but no correlation during the sharp increase in mechanical activation (treppe) when stimulation was resumed after a rest period. It is suggested that while total Ca cycling remains unchanged during the initial period of tension treppe, the free Ca2+ transient and mechanical activation increase sharply due to resaturation of high affinity Ca2+ buffers, other than troponin C, depleted of Ca2+ during the rest period. |
| Databáze: | OpenAIRE |
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