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First published online December 9, 2004

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Ca²⁺ machinery limits globalization

Ca²⁺ is an interesting intracellular messenger because local rises in its concentration – `sparks' – can trigger global Ca²⁺ waves that spread across the cell. Frequently, this involves Ca²⁺-induced Ca²⁺ release (CICR), in which Ca²⁺ sparks stimulate release of further Ca²⁺ from intracellular stores through ryanodine receptors. Llewelyn Roderick and co-workers now show that in cardiomyocytes the subcellular geography of the Ca²⁺ signalling machinery usually prevents this so the cells do not contract inappropriately (see p. 6327). Combining confocal microscopy and electrophysiology, they show the peripheral sparks generated during normal twitching do not produce Ca²⁺ waves that spread into the interior of the cell – which would stimulate excessive contraction. Instead Ca²⁺ pumps on mitochondria and the sarcoplasmic reticulum mop up the Ca²⁺ signal before it can spread. When the authors inhibit these pumps, global Ca²⁺ waves are generated, producing a more profound twitch. Exciting cells with physiological agonists has a similar effect, overcoming the effect of the pumps. The authors' findings indicate that the fine structure of the Ca²⁺ signalling system determines the profile of excitation-contraction coupling in cardiomyocytes and thereby plays an important role in gross cardiac physiology.

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The spatial pattern of atrial cardiomyocyte calcium signalling modulates contraction

Lauren Mackenzie, H. Llewelyn Roderick, Michael J. Berridge, Stuart J. Conway, and Martin D. Bootman
JCS 2004 117: 6327-6337. [Abstract] [Full Text]  

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in JCS Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Search for Related Content