Whole-cell currents from the cloned canine cardiac Na+/Ca2+ exchanger NCX1 overexpressed in a fibroblast cell CCL39.
A conventional patch-clamp technique was used to record the whole-cell current from the cloned canine cardiac Na+/Ca2+ exchanger NCX1 overexpressed in a fibroblast cell. Ca2+ was extracellularly applied to the Na+-loaded cell to activate the outward current by operating the reverse mode of NCX1. No measurable outward current was ever elicited from the nontransfected cell. Na+/Ca2+ exchange blocker 5 mM Ni2+ or 3 microM KB-R7943 that was applied extracellularly abolished the outward current. With 140 mM external Li+ (replacing Na+), the outward current was transient during the Ca2+ application. In contrast, with 140 mM external Na+, the outward current was maintained without any inactivation during the Ca2+ application. I-V relations predicted from the whole-cell clamp protocols used were obtained both before and during the Ca2+ application. The exchanger whole-cell currents are thus successfully detectable from NCX1 which is overexpressed in this stable transfectant system.
Uehara
A
A
Department of Physiology, School of Medicine, Fukuoka University, Jonan-ku, Fukuoka 814-80, Japan.
Iwamoto
T
T
Shigekawa
M
M
Imanaga
I
I
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D003001:Cloning, Molecular; D006224:Cricetinae; D004285:Dogs; D015870:Gene Expression; D017136:Ion Transport; D009206:Myocardium / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D012964:Sodium / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger; D014162:Transfection
D002352:Carrier Proteins; D019831:Sodium-Calcium Exchanger; D012964:Sodium; D002118:Calcium