%0 Journal Article %T Excitation-contraction coupling in heart: new insights from Ca2+ sparks %+ National Institute on Aging [Bethesda, USA] (NIA) %+ University of Maryland School of Medicine %A Cheng, H %A Lederer, M, R %A Xiao, R-P %A Gómez, Ana Maria %A Zhou, Y-y %A Zimanl, H %A Spurgeon, E, G %A Lakatta, E, G %A Lederer, W, J %< avec comité de lecture %@ 0143-4160 %J Cell Calcium %I Elsevier %V 20 %N 2 %P 129-140 %8 1996 %D 1996 %Z Life Sciences [q-bio]/Human health and pathology/Cardiology and cardiovascular systemJournal articles %X Ca2+ sparks, the elementary units of sarcoplasmic reticulum (SR) Ca2+ release in cardiac, smooth and skeletal muscle are localized (24 pm) increases in intracellular Ca2+ concentration, [Ca'+],, that last briefly (30-l 00 ms). These Ca2+ sparks arise from the openings of a single SR Ca2+ release channel (ryanodine receptor, RyR) or a few RyRs acting in concert. In heart muscle, Ca2+ sparks can occur spontaneously in quiescent cells at a low rate (100 s-l per cell). Identical Ca2+ sparks are also triggered by depolarization because the voltage-gated sarcolemmal L-type Ca2+ channels (dihydropyridine receptors, DHPRs) locally increase [Ca'+], and thereby activate the RyRs by Ca'+-induced Ca2+ release (CICR). The exquisite responsiveness of this process, reflected by the ability of even a single DHPR to activate a Ca2+ spark, is perhaps due to the large local increase in [Ca2+], in the vicinity of the RyR that is a consequence of the close apposition of the DHPRs and the RyRs. In this review we examine our current understanding of cardiac excitation-contraction (EC) coupling in light of recent studies on the elementary Ca2+ release events or Ca2+ sparks. In addition, we further characterized Ca2+ spark properties in rat and mouse heart cells. Specifically we have determined that: (i) Ca2+ sparks occur at the junctions between the transverse-tubules and the SR in both species; (ii) Ca2+ sparks are asymmetric, being 18% longer in the longitudinal direction than in the transverse direction; and (iii) Ca2+ sparks individually do not produce measurable sarcomere shortening (< 1%). These results are discussed with respect to local activation of the RyRs, the stability of CICR, Ca2+ diffusion, and the theory of EC coupling. %G English %2 https://inserm.hal.science/inserm-02477341/document %2 https://inserm.hal.science/inserm-02477341/file/1996CellCalcium.pdf %L inserm-02477341 %U https://inserm.hal.science/inserm-02477341 %~ INSERM %~ CARDIO