Deutsche Übersetzung des Titels: Biophysikalische Analyse der räumlichen und zeitlichen Verteilung freier Ca2+-Ionen in Mikro- und Nanodomänen von Muskelzellen

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Übersetzung des Abstracts (Englisch)

This work establishes methods to measure and quantify the spatial and temporal changes of the free Ca2+ ion concentration ([Ca2+]) inside skeletal muscle fibers and to calculate the underlying Ca2+ release from the sarcoplasmic reticulum (SR) caused by the opening of Ca2+ permeable ion channels (RyRs). The recording of microdomain Ca2+ signals (spatially averaged measurements of transient increases in myoplasmic [Ca2+]), was achieved by epi-illumination microscopy utilizing changes in the absorption of the Ca2+ indicator Antipyrylazo III. Nanodomain Ca2+ signals, the brief and highly localized spatio-temporal changes in [Ca2+] caused by elementary Ca2+ release events, were measured with submicron precision and a time resolution of 2 ms using confocal laser scanning fluorescence microscopy. The underlying release rate of Ca2+ ions from the SR was calculated using the most detailed information about intracellular Ca2+ buffers and Ca2+ pumps currently available. With these quantitative tools this work lead to the conclusion that the elementary events of Ca2+ release are generated by the opening of more than one RyR. Striking morphological differences between elementary Ca2+ release events measured under different experimental conditions are revealed, which can be explained by the molecular structure of the Ca2+ release source. For the first time this work presents measurements of Ca2+ sparks in adult mammalian muscle with high abundance which is of significant importance for medical diseases involving pathophysiological changes in Ca2+ regulation.