The contribution of the sarcoplasmic reticulum Ca2+-transport ATPase to caffeine-induced Ca2+ transients of murine skinned skeletal muscle fibres

• Verfasst von: Makabe, Makoto [VerfasserIn]
• Verfasst von: Werner, Oliver [VerfasserIn]
• Verfasst von: Fink, Rainer [VerfasserIn]
• Titel: The contribution of the sarcoplasmic reticulum Ca2+-transport ATPase to caffeine-induced Ca2+ transients of murine skinned skeletal muscle fibres
• Verf.angabe: Makoto Makabe, Oliver Werner, Rainer H.A. Fink
• E-Jahr: 1996
• Jahr: 01 August 1996
• Umfang: 10 S.
• Fussnoten: Im Titel ist "2+" hochgestellt ; Gesehen am 11.02.2025
• Titel Quelle: Enthalten in: Pflügers Archiv
• Ort Quelle: Berlin : Springer, 1868
• Jahr Quelle: 1996
• Band/Heft Quelle: 432(1996), 4, Seite 717-726
• ISSN Quelle: 1432-2013
• DOI: doi:10.1007/s004240050190
• Datenträger: Online-Ressource
• Sprache: eng
• Sach-SW: Caffeine
• Sach-SW: Cyclopiazonic acid
• Sach-SW: Mouse muscle
• Sach-SW: Sarcoplasmic reticulum
• Sach-SW: Skinned fibres
• Sach-SW: SR Ca2+-transport ATPase
• K10plus-PPN: 1916847986

Abstract

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.