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lüll Calcium biology of the transverse tubules in heart Song LS; Guatimosim S; Gomez-Viquez L; Sobie EA; Ziman A; Hartmann H; Lederer WJAnn N Y Acad Sci 2005[Jun]; 1047 (ä): 99-111Ca(2+) sparks in heart muscle are activated on depolarization by the influx of Ca(2+) through dihydropyridine receptors in the sarcolemmal (SL) and transverse tubule (TT) membranes. The cardiac action potential is thus able to synchronize the [Ca(2+)](i) transient as Ca(2+) release is activated throughout the cell. Increases in the amount of Ca(2+) within the sarcoplasmic reticulum (SR) underlie augmented Ca(2+) release globally and an increase in the sensitivity of the ryanodine receptors (RyRs) to be triggered by the local [Ca(2+)](i). In a similar manner, phosphorylation of the RyRs by protein kinase A (PKA) increases the sensitivity of the RyRs to be activated by local [Ca(2+)](i). Heart failure and other cardiac diseases are associated with changes in SR Ca(2+) content, phosphorylation state of the RyRs, [Ca(2+)](i) signaling defects and arrhythmias. Additional changes in transverse tubules and nearby junctional SR may contribute to alterations in local Ca(2+) signaling. Here we briefly discuss how TT organization can influence Ca(2+) signaling and how changes in SR Ca(2+) release triggering can influence excitation-contraction (EC) coupling. High speed imaging methods are used in combination with single cell patch clamp experiments to investigate how abnormal Ca(2+) signaling may be regulated in health and disease. Three issues are examined in this presentation: (1) normal Ca(2+)-induced Ca(2+) release and Ca(2+) sparks, (2) abnormal SR Ca(2+) release in disease, and (3) the triggering and propagation of waves of elevated [Ca(2+)](i).|Animals[MESH]|Calcium Signaling/*physiology[MESH]|Electrophysiology[MESH]|Humans[MESH]|Myocytes, Cardiac/*metabolism[MESH]|Ryanodine Receptor Calcium Release Channel/physiology[MESH]|Sarcomeres/*physiology/ultrastructure[MESH]|Sarcoplasmic Reticulum/*physiology/ultrastructure[MESH] |