Local calcium transients triggered by single L-type calcium channel currents in cardiac cells.
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.
López-López
J R
JR
Department of Physiology, University of Maryland, School of Medicine, Baltimore 21201, USA.
Shacklock
P S
PS
Balke
C W
CW
Wier
W G
WG
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation; D006168:Guinea Pigs; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D018613:Microscopy, Confocal; D009206:Myocardium / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011336:Probability; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology
D015220:Calcium Channels; D014700:Verapamil; D002118:Calcium