Characteristics and a functional implication of Ca(2+)-activated K(+) current in mouse aortic endothelial cells.
We employed the patch-clamp technique to investigate a Ca(2+)-activated K(+) (K(Ca)) current in cultured mouse aortic endothelial cells (MAECs). In the whole-cell mode, an increase in cytosolic [Ca(2+)] ([Ca(2+)](i)) to 2 micro M activated an outwards current. The [K(+)](o)-dependent change of the reversal potentials agreed well with the predicted Nernstian relation, suggesting that it was a K(Ca) current. The Hill coefficient (4) and EC(50) (740 nM) were obtained from the current/[Ca(2+)](i) relationship. Iberiotoxin (50 nM) or apamin (200 nM) failed to inhibit the current, whereas TEA (10 mM) suppressed the current to 73.6+/-1.6% of control ( n=9). The intermediate-conductance, Ca(2+)-activated K(+) (IK(Ca)) channel blockers charybdotoxin (50 nM), clotrimazole (10 micro M) and econazole (10 micro M) inhibited the K(Ca) current to 10.5+/-1.3% ( n=6), 16.6+/-3.1% ( n=6), and 19.3+/-2.5% ( n=5) of control, respectively. The IK(Ca) channel openers chlorzoxazone, zoxazolamine and 1-ethyl-2-benz-imidazolinone and the Ca(2+)-activated Cl(-) channel blocker niflumic acid activated the K(Ca) current. In inside-out patches, the single-channel conductance was 17.7 pS in symmetrical K(+) solutions. RT-PCR analysis showed transcripts of the murine IK1 channel (mIK1) in MAECs. The IK(Ca) channel blockers inhibited the ATP-induced [Ca(2+)](i) increase in MAECs and the endothelium-dependent relaxation of mouse aortic rings. In addition, the IK(Ca) channel openers augmented ATP-induced [Ca(2+)](i) increase in MAECs and evoked endothelium-dependent relaxation of mouse aorta. These results suggest that an mIK1-like channel mediates the native IK(Ca) current in MAECs and may contribute to endothelium-dependent relaxation by modulating MAEC [Ca(2+)](i).
Ahn
Seung Cheol
SC
Department of Physiology, College of Medicine, Dankook University, Cheonan, Republic of Korea.
Seol
Geun Hee
GH
Kim
Ji Aee
JA
Suh
Suk Hyo
SH
D000818:Animals; D001011:Aorta / Q000033:anatomy & histology*; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D018118:Chloride Channels / Q000037:antagonists & inhibitors; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D005260:Female; D008297:Male; D051379:Mice; D009125:Muscle Relaxants, Central / Q000494:pharmacology; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D009544:Niflumic Acid / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
D018118:Chloride Channels; D009125:Muscle Relaxants, Central; D026902:Potassium Channel Blockers; D024681:Potassium Channels, Calcium-Activated; D009544:Niflumic Acid; D002118:Calcium