Differing Effects of Inotropic Agents on Length Change Deactivation of Isolated Rat Myocardium
| Autor: | Betty J. Skipper, John M. Perea, Laura A. Grimes, Lincoln E. Ford, John K. Leach |
|---|---|
| Rok vydání: | 2002 |
| Předmět: |
Inotrope
Cardiac function curve medicine.medical_specialty Cardiotonic Agents Contraction (grammar) Epinephrine chemistry.chemical_element Isometric exercise In Vitro Techniques Calcium General Biochemistry Genetics and Molecular Biology Rats Sprague-Dawley Caffeine Internal medicine medicine Animals Cardiac muscle General Medicine Papillary Muscles Myocardial Contraction Rats Surgery medicine.anatomical_structure chemistry Length change Cardiology medicine.drug |
| Zdroj: | Journal of Investigative Medicine. 50:61-66 |
| ISSN: | 1708-8267 1081-5589 |
| DOI: | 10.2310/6650.2002.33519 |
| Popis: | Background A rapid change in length of cardiac muscle during isometric contraction is followed by developed force that is less than appropriate for the new length because of deactivation of the contractile system. Length change deactivation may have favorable or unfavorable effects on cardiac function, depending on the circumstances under which it is produced. Methods Left ventricular papillary muscles from male Sprague-Dawley rats were arranged for recording of isometric force. After each control or reference isometric contraction, a quick release-quick stretch V-step was applied to the following contraction. For each repetition of control and experimental contractions, the time of application of V-steps was increased by 20 ms until peak force was reached. Effects of these V-steps were assessed from ratios of peak redeveloped force to peak force in an isometric reference contraction. Slopes of plots of these ratios versus time after the onset of the contraction were used to quantify the effects of inotropic agents on deactivation. Results Increasing calcium from 2.5 to 5.0 or 7.5 mM increased force by 12±4% (mean±SEM), did not change time to peak, and did not significantly alter the deactivation slope. Adding 5 mM epinephrine increased force by 16±5%, decreased time to peak by 34±3%, and increased the deactivation slope by 106±9% ( PConclusions The quantitatively different effects of the three agents on length change deactivation slopes and time to peak force suggest a common mechanism, probably involving thin-filament cooperativity. |
| Databáze: | OpenAIRE |
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