Regulation of calcium release is gated by calcium current, not gating charge, in cardiac myocytes.
In skeletal muscle, intramembrane charge movement initiates the processes that lead to the release of calcium from the sarcoplasmic reticulum. In cardiac muscle, in contrast, the similarity of the voltage dependence of developed tension and intracellular calcium transients to that of calcium current suggests that the calcium current may gate the release of calcium. Nevertheless, a mechanism similar to that of skeletal muscle continues to be postulated for cardiac muscle. By using rapid exchange (20 to 50 milliseconds) of the extracellular solutions in rat ventricular myocytes in which the intracellular calcium transients or cell shortening were measured, it has now been shown that the influx of calcium through the calcium channel is a mandatory link in the processes that couple membrane depolarization to the release of calcium. Thus, intramembrane charge movement does not contribute to the release of calcium in heart muscle.
Näbauer
M
M
University of Pennsylvania, Department of Physiology, Philadelphia 19104.
Callewaert
G
G
Cleemann
L
L
Morad
M
M
D000818:Animals; D001464:Barium / Q000378:metabolism / Q000494:pharmacology; D001572:Benzofurans; D002021:Buffers; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology*; D003956:Dialysis; D004533:Egtazic Acid / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D005456:Fluorescent Dyes; D016257:Fura-2; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D006352:Heart Ventricles; D008564:Membrane Potentials; D009200:Myocardial Contraction; D051381:Rats; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D013050:Spectrometry, Fluorescence
D001572:Benzofurans; D002021:Buffers; D015220:Calcium Channels; D005456:Fluorescent Dyes; D001464:Barium; D004533:Egtazic Acid; D012964:Sodium; D002118:Calcium; D016257:Fura-2