[Inhibition of potassium channel by chronic hypoxia on pulmonary artery smooth muscle cells in rats].
OBJECTIVE
To explore the possible effect of potassium channel in chronic hypoxic pulmonary hypertension.


METHODS
Male Wistar rats were placed in the identical normobaric or hypoxic environmental chamber. In one chamber, rats were maintained in 10% +/- 0.5% O2(by displacement with N2) for 3 weeks, whereas in the other, rats were maintained in air. The single smooth muscle cell was isolated from pulmonary artery (phi 200-700 microns) of Wistar rats with acute enzymatic digestion method. Using patch-clamp technique, we recorded the outward K+ currents in pulmonary artery smooth muscle cells and identified a Ca2+.ATP activated K+ channel (K+Ca-ATP) and a delayed rectifier K+ channel among the outward K+ currents. We compared the activities of Ca2+.ATP activated K+ channel (K+Ca-ATP) or delayed rectifier K+ channel in smooth muscle cells isolated from pulmonary artery of chronic hypoxic and normoxic rats.


RESULTS
The activities of Ca2+.ATP activated K+ channel (K+Ca-ATP) and delayed rectifier K+ channel in chronic hypoxic group are much lower than that in normal group (T test, P < 0.01). Cromakalim (10 mmol) caused a marked enhancement of activity of the reduced K+Ca-ATP but not the delayed rectifier K+ channel in rats of hypoxic group.


CONCLUSIONS
The persistent decrease of potassium channel activity may contribute to setting the development of chronic hypoxic pulmonary hypertension. Cromakalim, one of potassium channel openers, can decrease the pulmonary hypertension induced by chronic hypoxia and may be a new effective drug for treatment of hypoxic pulmonary hypertension.
Xiao
X
X
Respiratory Department, First Hospital Affiliated to West China University of Medical Science, Chendu 610041.
Chen
W
W
Cheng
D
D
D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D002469:Cell Separation; D019806:Cromakalim / Q000494:pharmacology; D006976:Hypertension, Pulmonary / Q000209:etiology / Q000503:physiopathology; D000860:Hypoxia / Q000150:complications / Q000503:physiopathology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000473:pathology*; D015221:Potassium Channels / Q000187:drug effects; D011651:Pulmonary Artery / Q000473:pathology; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar
D000959:Antihypertensive Agents; D015221:Potassium Channels; D019806:Cromakalim