Prolonged biphasic strontium-mediated contractions of cat and frog heart muscle and their response to inotropic influences
| Autor: | Andrew H. Henderson, M.R. Cattell |
|---|---|
| Rok vydání: | 1976 |
| Předmět: |
Inotrope
medicine.medical_specialty Contraction (grammar) Epinephrine chemistry.chemical_element chemistry.chemical_compound Species Specificity Heart Rate Lanthanum Internal medicine medicine Extracellular Animals Molecular Biology Papillary muscle Manganese Strontium Endoplasmic reticulum Temperature Rana esculenta Depolarization Myocardial Contraction Stimulation Chemical medicine.anatomical_structure Endocrinology chemistry Cats Calcium Cardiology and Cardiovascular Medicine Caffeine |
| Zdroj: | Journal of Molecular and Cellular Cardiology. 8:299-319 |
| ISSN: | 0022-2828 |
| DOI: | 10.1016/0022-2828(76)90005-5 |
| Popis: | Prolonged biphasic strontium (Sr)-mediated contractions of cat and frog heart muscle preparations have been studied in order to characterize the twitch and plateau phases by their responses to inotropic influences. Plateau force appeared intrinsically independent of frequency in the cat, but was frequency-dependent in the frog. Inotropic interventions (temperature, Sr, manganese, lanthanum, adrenaline, caffeine) directly altered plateau force in mid-contraction in both species. The twitch component in cat muscles was relatively large, frequency-dependent, augmented by adrenaline, and characterized by a slower onset than in Ca-mediated contractions. In frog muscles the smaller twitch appeared frequency-dependent but remained a constant function of plateau height, and its onset was not slower than with Ca. The transition from Ca to Sr-mediated contractions was slow in both species. The findings suggest that the initial twitch component is related to Sr released from cellular stores; that its slower onset in cat muscles implies a different release mechanism and/or site from frog; that availability of extracellular Sr during depolarization can directly influence activation in both species; and that sequestration/removal of Sr is relatively more effective during depolarization in cat than frog muscles, but more temperature-dependent at the end of contraction, implying different dominant mechanisms. These species differences are consistent with differences in the relative importance of sarcoplasmic reticulum and sarcolemmal membrane function in supplying and removing activating cation to and from the contractile sites. |
| Databáze: | OpenAIRE |
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