Run-down of calcium current is related to intracellular sodium.
Run-down of Ca2+ current was studied in isolated guinea pig ventricular cells and it was found to be attenuated by intracellular sodium. Calcium currents were recorded after activation of Na+ channels by a step pulse. The "run-down" in 30 min was significantly reduced compared with control cells. When NaCl (0.1-10 mM) diffused from the micropipette into the cells, run-down of Ca2+ current was also significantly attenuated. However, the resulted increase of intracellular Na+ did not affect voltage dependent activation of Ca2+ current, but the duration of the action potential was shortened slightly.
Wang
X L
XL
Department of Pharmacology, Chinese Academy of Medical Sciences, Beijing.
Hua
Z
Z
Zhang
L M
LM
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D006321:Heart / Q000502:physiology*; D006352:Heart Ventricles; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D012964:Sodium / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology; D013552:Swine; D013997:Time Factors
D015220:Calcium Channels; D012965:Sodium Chloride; D012964:Sodium