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(Circulation Research. 2003;93:4.)
© 2003 American Heart Association, Inc.

Editorials

Illuminating Sarcoplasmic Reticulum Calcium

L. Venetucci, A.W. Trafford, D.A. Eisner

From the Unit of Cardiac Physiology, University of Manchester, Manchester, UK.

Correspondence to D.A. Eisner, Unit of Cardiac Physiology, 1.524 Stopford Bldg, University of Manchester, Oxford Road, Manchester M13 9PT. E-mail eisner@man.ac.uk

Key Words: calcium • sarcoplasmic reticulum • fluorescence

An extract of the first 250 words of the full text is provided, because this article has no abstract.

The bulk of the Ca²⁺ that activates contraction in the heart comes from the sarcoplasmic reticulum (SR). Calcium is released by the process of Ca²⁺-induced Ca²⁺ release (CICR) in which the entry of a small amount of Ca²⁺ across the cell membrane triggers the release of much more from the SR. This mechanism depends on the fact that Ca²⁺ entry from the extracellular fluid (via the L-type Ca²⁺ current) increases the probability that the SR Ca²⁺ release channel (ryanodine receptor, RyR) is open. The greater the open probability of the RyR, the greater the release of Ca²⁺ from the SR and therefore the larger the contraction of the heart. A major factor determining the contractility of the heart is the Ca²⁺ content of the SR. As one might expect, the more Ca²⁺ that there is in the SR, the more is released on each contraction. However the degree of filling of the SR has other important implications for cardiac physiology and pathology. Excessive filling of the SR (Ca²⁺ overload) results in Ca²⁺ release even in the absence of a trigger. When this Ca²⁺ release occurs in diastole, it can activate inward membrane currents and produce afterdepolarizations. In the field of heart failure, the decrease of the systolic Ca²⁺ transient is generally associated with a decrease of SR Ca²⁺ content, although the precise mechanisms responsible for this remain controversial.^1,2

Given the importance of SR Ca²⁺ content, it is essential to be able to measure it. Many previous studies have used . . . [Full Text of this Article]

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