Non-selective cation current of guinea-pig endocardial endothelial cells.
1. Endocardial endothelial (EE) cells, isolated by the enzymatic treatment of guinea-pig heart, were used for whole-cell voltage clamp experiments. 2. The inward rectifier K+ current was observed in about half of the experiments. The contribution of Ca(2+)-dependent K+ current to the resting membrane conductance was also suggested. 3. After the K+ conductances were suppressed, removal of external Na+ revealed an inward cation current (1.2 pA pF-1, at -45 mV), whose slope conductance was a saturable function of external Na+ concentration. When Na+ was totally replaced by various monovalent cations, the order of the membrane conductances was K+ > Rb+ > Cs+ > Na+ > Li+. 4. This basal non-selective cation current was blocked by either Gd3+ or La3+, and showed slight outward rectification. 5. Addition of 20 mM Ca2+ or Ba2+, but not Mg2+ or Mn2+, to the Na(+)-free solution, induced an inward current, indicating that this current possesses a significant Ca2+ permeability. 6. In approximately 15% of the experiments, ATP and histamine induced another type of non-selective cation current, which showed different ion selectivity (Na+ > K+, Cs+) and rectification (inward). 7. The basal non-selective cation current is responsible for both the low resting potential and the leak Ca2+ influx of EE cells.
Manabe
K
K
Department of Physiology, Faculty of Medicine, Kyoto University, Japan.
Takano
M
M
Noma
A
A
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects; D004533:Egtazic Acid / Q000494:pharmacology; D004699:Endocardium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004727:Endothelium / Q000187:drug effects / Q000378:metabolism; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
D007473:Ion Channels; D004533:Egtazic Acid; D006632:Histamine; D000255:Adenosine Triphosphate; D012964:Sodium; D011188:Potassium; D002118:Calcium