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Science. 1995 May 19;268(5213):1042-5.

Local calcium transients triggered by single L-type calcium channel currents in cardiac cells.

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Department of Physiology, University of Maryland, School of Medicine, Baltimore 21201, USA.


Excitation-contraction coupling was studied in mammalian cardiac cells in which the opening probability of L-type calcium (Ca2+) channels was reduced. Confocal microscopy during voltage-clamp depolarization revealed distinct local transients in the concentration of intracellular calcium ions ([Ca2+]i). When voltage was varied, the latency to occurrence and the relative probability of occurrence of local [Ca2+]i transients varied as predicted if Ca2+ release from the sarcoplasmic reticulum (SR) was linked tightly to Ca2+ flux through L-type Ca2+ channels but not to that through the Na-Ca exchanger or to average [Ca2+]i. Voltage had no effect on the amplitude of local [Ca2+]i transients. Thus, the most efficacious "Ca2+ signal" for activating Ca2+ release from the SR may be a transient microdomain of high [Ca2+]i beneath an individual, open L-type Ca2+ channel.

[Indexed for MEDLINE]

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