Local Ca2+ Signaling and EC Coupling in Heart: Ca2+ Sparks and the Regulation of the [Ca2+]i Transient

S. Guatimosim, K. Dilly, L. F. Santana, M. S. Jafri, E. A. Sobie and W. J. Lederer. Local Ca2+ Signaling and EC Coupling in Heart: Ca2+ Sparks and the Regulation of the [Ca2+]i Transient. Journal of Molecular and Cellular cardiology (2002) 34, 941–950. The elementary event of Ca2+ release in heart is the Ca2+ spark. It occurs at a low rate during diastole, activated only by the low cytosolic [Ca2+]i. Synchronized activation of many sparks is due to the high local [Ca2+]i in the region surrounding the sarcoplasmic reticulum (SR) Ca2+ release channels and is responsible for the systolic [Ca2+]i transient. The biophysical basis of this calcium signaling is discussed. Attention is placed on the local organization of the ryanodine receptors (SR Ca2+ release channels, RyRs) and the other proteins that underlie and modulate excitation–contraction (EC) coupling. A brief review of specific elements that regulate SR Ca2+ release (including SR lumenal Ca2+ and coupled gating of RyRs) is presented. Finally integrative calcium signaling in heart is presented in the context of normal heart function and heart failure.