[Inhibition of voltage-gated K+ current in rat intrapulmonary arterial smooth muscle cells by endothelin-1].
OBJECTIVE
To investigate the role of endothelin-1 (ET-1) in the physiological and pathophysiological regulating mechanisms of voltage-gated K+ current (IKV) inhibition in rat intrapulmonary arterial smooth muscle cells (PASMCs).


METHODS
Single PASMCs were obtained with acute enzyme (collagnase plus papain) dispersing method. Using whole cell patch-clamp technique in freshly isolated rat PASMCs, the effect of ET-1 on voltage-gated K+ current was recorded.


RESULTS
ET-1 (1 x 10(-9) mol.L-1) and the voltage-dependent K+ (KV)-channel antagonist 4-aminopyridine (4AP), but not the Ca(2+)-activated K(+)-channel antagonist tetraethylammonium (TEA), caused membrane depolarization. The effect of ET-1 on membrane potential persisted in cells in which intracellular Ca2+ was buffered with 1,2-bis (2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid (BAPTA). ET-1 (1 x 10(-9) mol.L-1) caused a significant reversible inhibition of KV current, which began 4.0 s after application of ET-1, was much earlier than the effect of membrane depolarization of PASMCs (15s). ET-1 (1 x 10(-10) to 1 x 10(-7) mol.L-1) caused a concentration-dependent inhibition of K+ current ( mV, from 136 to 40 pA/pF). The percent inhibition was 71% at 1 x 10(-7) mol.L-1 (n = 6). The effect of ET-1 (1 x 10(-9) mol.L-1) on K+ current was weaker under conditions free of Ca2+ than containing Ca2+. At a test potential of  mV, free of Ca2+ conditions reduced the maximum inhibitory effect of ET-1 from 71% to 50%.


CONCLUSIONS
ET-1 modulated pulmonary vascular reactivity by depolarizing membrane potential and inhibiting the K+ current of PASMCs. The effect of ET-1 on PASMCs membrane potential and the inhibition of K+ current were independent of Ca2+, but the inhibition of K+ current was much greater under conditions containing Ca2+ than free of Ca2+.
Fan
Zai-wen
ZW
Pulmonary Disease Laboratory of Ministry of Health of China, Affiliated Tongji Hospital, Tongji Medical College of Huazhong University of Science and Technology, Wuhan 430030, China. zaiwenfan@163.net
Zhang
Zhen-xiang
ZX
Xu
Yong-jian
YJ
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002469:Cell Separation; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024642:Potassium Channels, Voltage-Gated / Q000187:drug effects*; D011651:Pulmonary Artery / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D019789:Tetraethylammonium / Q000494:pharmacology
D019332:Endothelin-1; D026902:Potassium Channel Blockers; D024642:Potassium Channels, Voltage-Gated; D019789:Tetraethylammonium; D002118:Calcium