The contribution of the sarcoplasmic reticulum Ca2+-transport ATPase to caffeine-induced Ca2+ transients of murine skinned skeletal muscle fibres
The present study was carried out to investigate the contribution of the Ca2+-transport ATPase of the sarcoplasmic reticulum (SR) to caffeine-induced Ca2+ release in skinned skeletal muscle fibres. Chemically skinned fibres of balb-C-mouse EDL (extensor digitorum longus) were exposed for 1 min to a...
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| Hauptverfasser: | , , |
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| Dokumenttyp: | Article (Journal) |
| Sprache: | Englisch |
| Veröffentlicht: |
01 August 1996
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| In: |
Pflügers Archiv
Year: 1996, Jahrgang: 432, Heft: 4, Pages: 717-726 |
| ISSN: | 1432-2013 |
| DOI: | 10.1007/s004240050190 |
| Online-Zugang: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1007/s004240050190
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| Verfasserangaben: | Makoto Makabe, Oliver Werner, Rainer H.A. Fink |
| Zusammenfassung: | The present study was carried out to investigate the contribution of the Ca2+-transport ATPase of the sarcoplasmic reticulum (SR) to caffeine-induced Ca2+ release in skinned skeletal muscle fibres. Chemically skinned fibres of balb-C-mouse EDL (extensor digitorum longus) were exposed for 1 min to a free Ca2+ concentration of 0.36 μM to load the SR with Ca2+. Release of Ca2+ from the SR was induced by 30 mM caffeine and recorded as an isometric force transient. For every preparation a pCa/force relationship was constructed, where pCa = − log10[Ca2+], In a new experimental approach, we used the pCa/force relationship to transform each force transient directly into a Ca2+ transient. The calculated Ca2+ transients were fitted by a double exponential function: Y0 + A1, · exp (−t/t1) + A2· exp(t /t2), with A1 < 0 < A2, t1 < t2and Y0, A1, A2 in micromolar. Ca2+ transients in the presence of the SR Ca2+-ATPase inhibitor cyclopiazonic acid (CPA) were compared to those obtained in the absence of the drug. We found that inhibition of the SR Ca2+-ATPase during caffeine-induced Ca2+ release causes an increase in the peak Ca2+ concentration in comparison to the control transients. Increasing CPA concentrations prolonged the time-to-peak in a dose-dependent manner, following a Hill curve with a half-maximal value of 6.5 ± 3 μM CPA and a Hill slope of 1.1 ± 0.2, saturating at 100 μM. The effects of CPA could be simulated by an extended three-compartment model representing the SR, the myofilament space and the external bathing solution. In terms of this model, the SR Ca2+-ATPase influences the Ca2+ gradient across the SR membrane in particular during the early stages of the Ca2+ transient, whereas the subsequent relaxation is governed by diffusional loss of Ca2+ into the bathing solution. |
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| Beschreibung: | Im Titel ist "2+" hochgestellt Gesehen am 11.02.2025 |
| Beschreibung: | Online Resource |
| ISSN: | 1432-2013 |
| DOI: | 10.1007/s004240050190 |