How does stochastic ryanodine receptor-mediated Ca leak fail to initiate a Ca spark?

ABSTRACT: Spontaneous calcium (Ca) sparks are initiated by single ryanodine receptor (RyR) opening. Once one RyR channel opens, it elevates local [Ca] in the cleft space ([Ca](Cleft)), which opens other RyR channels in the same Ca release unit (CaRU) via Ca-induced Ca-release. Experiments by Zima et al. (J. Physiol. 588:4743-4757, 2010) demonstrate that spontaneous Ca sparks occur only when intrasarcoplasmic-reticulum (SR) [Ca] ([Ca](SR)) is above a threshold level, but that RyR-mediated SR Ca leak exists without Ca sparks well below this threshold [Ca](SR). We examine here how single RyR opening at lower [Ca](SR) can fail to recruit Ca sparks at a CaRU, while still contributing to SR Ca leak. We assess this using a physiologically detailed mathematical model of junctional SR Ca release in which RyR

SUBMITTER: Sato D 

PROVIDER: S-EPMC3218344 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature