{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,12]],"date-time":"2026-06-12T06:20:02Z","timestamp":1781245202136,"version":"3.54.1"},"reference-count":58,"publisher":"Rockefeller University Press","issue":"1","content-domain":{"domain":["rupress.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2004,1,1]]},"abstract":"<jats:p>The purpose of this study was to quantify the Ca2+ fluxes underlying Ca2+ transients and their voltage dependence in myotubes by using the \u201cremoval model fit\u201d approach. Myotubes obtained from the mouse C2C12 muscle cell line were voltage-clamped and loaded with a solution containing the fluorescent indicator dye fura-2 (200 \u03bcM) and a high concentration of EGTA (15 mM). Ca2+ inward currents and intracellular ratiometric fluorescence transients were recorded in parallel. The decaying phases of Ca2+-dependent fluorescence signals after repolarization were fitted by theoretical curves obtained from a model that included the indicator dye, a slow Ca2+ buffer (to represent EGTA), and a sequestration mechanism as Ca2+ removal components. For each cell, the rate constants of slow buffer and transport and the off rate constant of fura-2 were determined in the fit. The resulting characterization of the removal properties was used to extract the Ca2+ input fluxes from the measured Ca2+ transients during depolarizing pulses. In most experiments, intracellular Ca2+ release dominated the Ca2+ input flux. In these experiments, the Ca2+ flux was characterized by an initial peak followed by a lower tonic phase. The voltage dependence of peak and tonic phase could be described by sigmoidal curves that reached half-maximal activation at \u221216 and \u221220 mV, respectively, compared with \u22122 mV for the activation of Ca2+ conductance. The ratio of the peak to tonic phase (flux ratio) showed a gradual increase with voltage as in rat muscle fibers indicating the similarity to EC coupling in mature mammalian muscle. In a subgroup of myotubes exhibiting small fluorescence signals and in cells treated with 30 \u03bcM of the SERCA pump inhibitor cyclopiazonic acid (CPA) and 10 mM caffeine, the calculated Ca2+ input flux closely resembled the L-type Ca2+ current, consistent with the absence of SR Ca2+ release under these conditions and in support of a valid determination of the time course of myoplasmic Ca2+ input flux based on the optical indicator measurements.<\/jats:p>","DOI":"10.1085\/jgp.200308908","type":"journal-article","created":{"date-parts":[[2003,12,16]],"date-time":"2003-12-16T01:33:59Z","timestamp":1071538439000},"page":"33-52","update-policy":"https:\/\/doi.org\/10.1085\/jgp.crossmarkpolicy","source":"Crossref","is-referenced-by-count":39,"title":["Voltage-dependent Ca2+ Fluxes in Skeletal Myotubes Determined Using a Removal Model Analysis"],"prefix":"10.1085","volume":"123","author":[{"given":"R.P.","family":"Schuhmeier","sequence":"first","affiliation":[{"name":"Universita\u0308t Ulm, Abteilung fu\u0308r Angewandte Physiologie Albert-Einstein-Allee 11, D-89069 Ulm, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"W.","family":"Melzer","sequence":"additional","affiliation":[{"name":"Universita\u0308t Ulm, Abteilung fu\u0308r Angewandte Physiologie Albert-Einstein-Allee 11, D-89069 Ulm, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"291","published-online":{"date-parts":[[2003,12,15]]},"reference":[{"key":"2023072520492916200_BIB1","doi-asserted-by":"crossref","first-page":"359","DOI":"10.1016\/S0143-4160(97)90029-4","volume":"21","year":"1997","journal-title":"Cell Calcium."},{"key":"2023072520492916200_BIB2","doi-asserted-by":"crossref","first-page":"625","DOI":"10.1113\/jphysiol.1983.sp014959","volume":"344","year":"1983","journal-title":"J. Physiol."},{"key":"2023072520492916200_BIB3","doi-asserted-by":"crossref","first-page":"151","DOI":"10.1113\/jphysiol.1988.sp017244","volume":"403","year":"1988","journal-title":"J. Physiol."},{"key":"2023072520492916200_BIB4","doi-asserted-by":"crossref","first-page":"297","DOI":"10.1085\/jgp.112.3.297","volume":"112","year":"1998","journal-title":"J. Gen. Physiol."},{"key":"2023072520492916200_BIB5","doi-asserted-by":"crossref","first-page":"283","DOI":"10.1016\/S0091-679X(08)60384-2","volume":"52","year":"1997","journal-title":"Methods Cell Biol."},{"key":"2023072520492916200_BIB6","doi-asserted-by":"crossref","first-page":"807","DOI":"10.1016\/S0006-3495(97)78113-X","volume":"73","year":"1997","journal-title":"Biophys. J."},{"key":"2023072520492916200_BIB7","doi-asserted-by":"crossref","first-page":"1171","DOI":"10.1016\/0092-8674(83)90300-8","volume":"32","year":"1983","journal-title":"Cell."},{"key":"2023072520492916200_BIB8","doi-asserted-by":"crossref","first-page":"297","DOI":"10.1085\/jgp.101.2.297","volume":"101","year":"1993","journal-title":"J. Gen. Physiol."},{"key":"2023072520492916200_BIB9","first-page":"211","volume":"148","year":"1995","journal-title":"J. Membr. Biol."},{"key":"2023072520492916200_BIB10","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1111\/j.1469-7793.1998.003by.x","volume":"513","year":"1998","journal-title":"J. Physiol."},{"key":"2023072520492916200_BIB11","doi-asserted-by":"crossref","first-page":"507","DOI":"10.1111\/j.1469-7793.2000.t01-1-00507.x","volume":"526","year":"2000","journal-title":"J. Physiol."},{"key":"2023072520492916200_BIB12","doi-asserted-by":"crossref","first-page":"d659","DOI":"10.2741\/dirksen","volume":"7","year":"2002","journal-title":"Front. Biosci."},{"key":"2023072520492916200_BIB13","doi-asserted-by":"crossref","first-page":"1695","DOI":"10.1073\/pnas.032657599","volume":"99","year":"2002","journal-title":"Proc. Natl. Acad. Sci. USA."},{"key":"2023072520492916200_BIB14","doi-asserted-by":"crossref","first-page":"149","DOI":"10.1016\/0076-6879(93)21014-Y","volume":"221","year":"1993","journal-title":"Methods Enzymol."},{"key":"2023072520492916200_BIB15","doi-asserted-by":"crossref","first-page":"709","DOI":"10.1113\/jphysiol.1993.sp019618","volume":"463","year":"1993","journal-title":"J. Physiol."},{"key":"2023072520492916200_BIB16","doi-asserted-by":"crossref","first-page":"373","DOI":"10.1085\/jgp.102.3.373","volume":"102","year":"1993","journal-title":"J. Gen. Physiol."},{"key":"2023072520492916200_BIB17","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1016\/0014-5793(87)80752-4","volume":"216","year":"1987","journal-title":"FEBS Lett."},{"key":"2023072520492916200_BIB18","doi-asserted-by":"crossref","first-page":"2333","DOI":"10.1016\/S0006-3495(99)77072-4","volume":"77","year":"1999","journal-title":"Biophys. J."},{"key":"2023072520492916200_BIB19","doi-asserted-by":"crossref","first-page":"635","DOI":"10.1016\/S0006-3495(88)83142-4","volume":"53","year":"1988","journal-title":"Biophys. J."},{"key":"2023072520492916200_BIB20"},{"key":"2023072520492916200_BIB21","doi-asserted-by":"crossref","first-page":"11061","DOI":"10.1073\/pnas.94.20.11061","volume":"94","year":"1997","journal-title":"Proc. Natl. Acad. Sci. USA."},{"key":"2023072520492916200_BIB22","doi-asserted-by":"crossref","first-page":"971","DOI":"10.1016\/S0006-3495(88)83178-3","volume":"53","year":"1988","journal-title":"Biophys. J."},{"key":"2023072520492916200_BIB23","doi-asserted-by":"crossref","first-page":"1089","DOI":"10.1016\/S0006-3495(88)83045-5","volume":"54","year":"1988","journal-title":"Biophys. J."},{"key":"2023072520492916200_BIB24","first-page":"73","volume":"V-3","year":"1974","journal-title":"R. A. I. R. O."},{"key":"2023072520492916200_BIB25","doi-asserted-by":"crossref","first-page":"34","DOI":"10.1145\/355769.355773","volume":"4","year":"1978","journal-title":"ACM Trans. Math. Softw."},{"key":"2023072520492916200_BIB26","doi-asserted-by":"crossref","first-page":"499","DOI":"10.1111\/j.1469-7793.2000.00499.x","volume":"525","year":"2000","journal-title":"J. Physiol."},{"key":"2023072520492916200_BIB27","doi-asserted-by":"crossref","first-page":"425","DOI":"10.1016\/S0143-4160(96)90005-6","volume":"20","year":"1996","journal-title":"Cell Calcium."},{"key":"2023072520492916200_BIB28","doi-asserted-by":"crossref","first-page":"59","DOI":"10.1016\/0304-4157(94)00014-5","volume":"1241","year":"1995","journal-title":"Biochim. Biophys. Acta."},{"key":"2023072520492916200_BIB29","doi-asserted-by":"crossref","first-page":"637","DOI":"10.1016\/S0006-3495(84)84203-4","volume":"45","year":"1984","journal-title":"Biophys. J."},{"key":"2023072520492916200_BIB30","doi-asserted-by":"crossref","first-page":"261","DOI":"10.1113\/jphysiol.1986.sp016008","volume":"372","year":"1986","journal-title":"J. Physiol."},{"key":"2023072520492916200_BIB31","doi-asserted-by":"crossref","first-page":"849","DOI":"10.1016\/S0006-3495(87)83413-6","volume":"51","year":"1987","journal-title":"Biophys. J."},{"key":"2023072520492916200_BIB32","doi-asserted-by":"crossref","first-page":"481","DOI":"10.1113\/jphysiol.1986.sp016059","volume":"373","year":"1986","journal-title":"J. Physiol."},{"key":"2023072520492916200_BIB33","doi-asserted-by":"crossref","first-page":"514","DOI":"10.1093\/oxfordjournals.jbchem.a123931","volume":"112","year":"1992","journal-title":"J. Biochem. (Tokyo)."},{"key":"2023072520492916200_BIB34","doi-asserted-by":"crossref","first-page":"72","DOI":"10.1038\/380072a0","volume":"380","year":"1996","journal-title":"Nature."},{"key":"2023072520492916200_BIB35","doi-asserted-by":"crossref","first-page":"255","DOI":"10.1016\/S0143-4160(97)90064-6","volume":"22","year":"1997","journal-title":"Cell Calcium."},{"key":"2023072520492916200_BIB36","doi-asserted-by":"crossref","first-page":"161","DOI":"10.1085\/jgp.112.2.161","volume":"112","year":"1998","journal-title":"J. Gen. Physiol."},{"key":"2023072520492916200_BIB37","doi-asserted-by":"crossref","first-page":"259","DOI":"10.1085\/jgp.106.2.259","volume":"106","year":"1995","journal-title":"J. Gen. Physiol."},{"key":"2023072520492916200_BIB38","doi-asserted-by":"crossref","first-page":"295","DOI":"10.1085\/jgp.102.2.295","volume":"102","year":"1993","journal-title":"J. Gen. Physiol."},{"key":"2023072520492916200_BIB39"},{"key":"2023072520492916200_BIB40","first-page":"d1195","volume":"7","year":"2002","journal-title":"Front. Biosci."},{"key":"2023072520492916200_BIB41","doi-asserted-by":"crossref","first-page":"31","DOI":"10.1085\/jgp.114.1.31","volume":"114","year":"1999","journal-title":"J. Gen. Physiol."},{"key":"2023072520492916200_BIB42","doi-asserted-by":"crossref","first-page":"365","DOI":"10.1085\/jgp.113.3.365","volume":"113","year":"1999","journal-title":"J. Gen. Physiol."},{"key":"2023072520492916200_BIB43","doi-asserted-by":"crossref","first-page":"1005","DOI":"10.1016\/S0006-3495(87)83430-6","volume":"51","year":"1987","journal-title":"Biophys. J."},{"key":"2023072520492916200_BIB44","doi-asserted-by":"crossref","first-page":"167","DOI":"10.1113\/jphysiol.1987.sp016775","volume":"392","year":"1987","journal-title":"J. Physiol."},{"key":"2023072520492916200_BIB45","doi-asserted-by":"crossref","first-page":"d1212","DOI":"10.2741\/A834","volume":"7","year":"2002","journal-title":"Front. Biosci."},{"key":"2023072520492916200_BIB46","doi-asserted-by":"crossref","first-page":"1065","DOI":"10.1016\/S0006-3495(03)74923-6","volume":"84","year":"2003","journal-title":"Biophys. J."},{"key":"2023072520492916200_BIB47","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1085\/jgp.107.1.1","volume":"107","year":"1996","journal-title":"J. Gen. Physiol."},{"key":"2023072520492916200_BIB48","doi-asserted-by":"crossref","first-page":"385","DOI":"10.1113\/jphysiol.1995.sp020820","volume":"486","year":"1995","journal-title":"J. Physiol."},{"key":"2023072520492916200_BIB49","doi-asserted-by":"crossref","first-page":"483","DOI":"10.1111\/j.1469-7793.1999.00483.x","volume":"521","year":"1999","journal-title":"J. Physiol."},{"key":"2023072520492916200_BIB50","doi-asserted-by":"crossref","first-page":"437","DOI":"10.1085\/jgp.97.3.437","volume":"97","year":"1991","journal-title":"J. Gen. Physiol."},{"key":"2023072520492916200_BIB51","doi-asserted-by":"crossref","first-page":"188","DOI":"10.1016\/0003-2697(84)90575-X","volume":"143","year":"1984","journal-title":"Anal. Biochem."},{"key":"2023072520492916200_BIB52","doi-asserted-by":"crossref","first-page":"677","DOI":"10.1111\/j.1469-7793.1998.677bd.x","volume":"512","year":"1998","journal-title":"J. Physiol."},{"key":"2023072520492916200_BIB53","doi-asserted-by":"crossref","first-page":"54","DOI":"10.1016\/S1050-1738(99)00003-1","volume":"9","year":"1999","journal-title":"Trends Cardiovasc. Med."},{"key":"2023072520492916200_BIB54","doi-asserted-by":"crossref","first-page":"415","DOI":"10.1085\/jgp.110.4.415","volume":"110","year":"1997","journal-title":"J. Gen. Physiol."},{"key":"2023072520492916200_BIB55","doi-asserted-by":"crossref","first-page":"447","DOI":"10.1111\/j.1469-7793.2000.00447.x","volume":"528","year":"2000","journal-title":"J. Physiol."},{"key":"2023072520492916200_BIB56","doi-asserted-by":"crossref","first-page":"134","DOI":"10.1038\/336134a0","volume":"336","year":"1988","journal-title":"Nature."},{"key":"2023072520492916200_BIB57","doi-asserted-by":"crossref","first-page":"1694","DOI":"10.1016\/S0006-3495(98)77881-6","volume":"74","year":"1998","journal-title":"Biophys. J."},{"key":"2023072520492916200_BIB58","doi-asserted-by":"crossref","first-page":"367","DOI":"10.1111\/j.1469-7793.2001.0367a.x","volume":"533","year":"2001","journal-title":"J. Physiol."}],"container-title":["The Journal of General Physiology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/rupress.org\/jgp\/article-pdf\/123\/1\/33\/1731906\/jgp123133.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/rupress.org\/jgp\/article-pdf\/123\/1\/33\/1731906\/jgp123133.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2023,7,25]],"date-time":"2023-07-25T20:51:28Z","timestamp":1690318288000},"score":1,"resource":{"primary":{"URL":"https:\/\/rupress.org\/jgp\/article\/123\/1\/33\/34178\/Voltage-dependent-Ca2-Fluxes-in-Skeletal-Myotubes"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2003,12,15]]},"references-count":58,"journal-issue":{"issue":"1","published-print":{"date-parts":[[2004,1,1]]}},"URL":"https:\/\/doi.org\/10.1085\/jgp.200308908","relation":{},"ISSN":["1540-7748","0022-1295"],"issn-type":[{"value":"1540-7748","type":"electronic"},{"value":"0022-1295","type":"print"}],"subject":[],"published":{"date-parts":[[2003,12,15]]}}}