Figure 2.

Origins of spontaneous Ca²⁺-release events (SCaEs). (A) Two representative examples of 50 × 18 matrices with heterogeneous RyR2 distribution (σ = 0.2). Red colors indicate high local RyR2 expression and blue colors low local RyR2 expression. The origins of individual Ca²⁺ waves are marked with crosses. Insets depict enlarged portions of the RyR2 distribution, showing that crosses mainly coincide with regions of high local RyR2 expression. (B) Histograms of relative RyR2 expression in all units (left) and units which were the origin of a SCaE (SCaE-inducing units). SCaEs arise mainly from units with high local RyR2 expression. (C) Mean relative RyR2 expression in SCaE-inducing units (squares) and all units (circles, 1.0 on average by definition) for different degrees of RyR2 heterogeneities. *indicates P < 0.05 vs. the group with heterogeneity 0.0 and ^#indicates P < 0.05 between mean relative RyR2 expression in SCaE-inducing units and all units; n = 6 per condition.