[Effect of endothelin-1 on voltage-gated K+ current in the pulmonary artery smooth muscle cells of chronic hypoxic rats].
OBJECTIVE
To investigate the effect of endothelin-1 (ET-1) on voltage-gated K+ current in the pulmonary artery smooth muscle cells (PASMCs) of chronic hypoxic rats.


METHODS
Twelve male Wistar rats matched with age and body weight were randomly divided into control and chronic hypoxic groups. Single PASMCs were obtained with acute enzyme (collagnase plus papain) dispersing method. Using the whole cell patch clamp technique in freshly isolated PASMCs from normoxic and hypoxic rats, the effects of ET-1 on voltage-gated K+ current were recorded.


RESULTS
The resting membrane potential (Em) in PASMCs from chronic hypoxic rats was significantly depolarized to (-32.6 +/- 1.3) mV compared with (-42.1 +/- 2.8) mV in PASMCs from normoxic rats (P < 0.01, n = 20). In chronic hypoxic rats, the IKv was smaller than that in normotensive rats [+50 mV, the peak current density of control group reduced from (136 +/- 24) pA/pF to (98 +/- 12) pA/pF, percent inhibition was (28.4 +/- 2.4)%, P < 0.01, n = 6]. Application of ET-1 (1 x 10(-8) mol x L(-1)) also depolarized PASMCs of chronic hypoxic rats from (-32.6 +/- 1.3) mV to (-21.5 +/- 1.7) mV (P < 0.05, n = 20) compared with the ET-1 induced depolarization from (-42.1 +/- 2.8) mV to (-22.6 +/- 1.4) mV (P < 0.05, n = 20). The change in membrane potential induced by ET-1 was not significantly different between PASMCs from normoxic and hypoxic rats. ET-1 (1 x 10(-10) to 1 x 10(-7) mol x L(-1)) caused concentration-dependent inhibition of K+ current in PASMCs both from normoxic and hypoxic rats. At higher concentration (1 x 10(-8) - 1 x 10(-7) mol x L(-1)), the effect of ET-1 on K+ current in PASMCs from hypoxic rats was greater than that of normoxic rats [+50 mV, the peak current density of control group reduced from (136 +/- 24) pA/pF to (40 +/- 10) pA/pF, percent inhibition was (71 +/- 7)%, that of hypoxic group was (98 +/- 6) pA/pF to (16 +/- 3) pA/pF, percent inhibition was (85 +/- 10)% at 1 x 10(-7) mol x L(-2), n = 6, P < 0.01].


CONCLUSIONS
Chronic hypoxia did not change the effect of ET-1 on the passive electrical properties of PASMCs. In both normotensive and chronic hypoxic hypertensive PASMCs, exogenous ET-1 could cause concentration-dependent inhibition of voltage-gated K+ current, and the inhibition of K+ current in PASMCs from chronic hypoxic rats was greater than that from normoxic rats at higher concentration (1 x 10(-8) - 1 x 10(-7) mol x L(-1)). Chronic hypoxia might alter the sensitivity of PASMCs to ET-1, perhaps PASMCs exposed to chronic hypoxia were more susceptible to ET-1 mediated IKv inhibition.
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; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000008:administration & dosage / Q000494:pharmacology*; D006976:Hypertension, Pulmonary / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D000860:Hypoxia / Q000150:complications*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects; D032389:Myocytes, Smooth Muscle / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D024642:Potassium Channels, Voltage-Gated / Q000187:drug effects*; D011651:Pulmonary Artery / Q000187:drug effects / Q000473:pathology; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar
D019332:Endothelin-1; D024642:Potassium Channels, Voltage-Gated