[The inhibition effect of acute hypoxia on K+Ca-ATP channels of pulmonary artery smooth muscle cells of rats].
OBJECTIVE
To explore the possible mechanism underlying hypoxic pulmonary vasoconstriction, we evaluated the effect of acute hypoxia on potassium channels in pulmonary artery smooth muscle cells.


METHODS
The single smooth muscle cell was freshly isolated from pulmonary artery (phi 700-200 microns) of Wistar rats with acute enzymatic digestion method. In symmetrical high K+ solution, we separated one outward K+ current from the patch of smooth muscle cells with inside-out configuration using patch-clamp technique. According to the electrophysiological response to the patch channel, this current was identified as the Ca2+, ATP activated potassium channel (K+Ca-ATP). The hypoxic solution was obtained by aeration with 5% CO2-balance N2 mixture.


RESULTS
The currents of K+Ca-ATP in the patch of smooth muscle cells was much inhibited while the oxygen tension of solution was reduced from normoxic (PO2 > or = 13.33 kPa) to hypoxic (PO2 < or = 2.67 kPa) levels (P < 0.01). Cromakalim (10 nmol/L), an opener of potassium channel, could activate the currents of K+Ca-ATP decreased by acute hypoxia (P < 0.01).


CONCLUSIONS
Acute hypoxia has an inhibition role on K+Ca-ATP currents in pulmonary artery smooth muscle cells, causes the membrane potentional depolarization, leads to pulmonary vasoconstriction, increases pulmonary vascular resistance and artery pressure. The decrease of K+Ca-ATP contributes to development of hypoxic pulmonary vasoconstriction. Cromakalim is one of effective antagonists for hypoxic pulmonary vasoconstriction.
Xiao
X
X
Respiratory Department, First Affiliated Hospital, West China University of Medical Science, Chengdu 610041.
Chen
W
W
Cheng
D
D
D000818:Animals; D015687:Cell Hypoxia; D002469:Cell Separation; D019806:Cromakalim / Q000494:pharmacology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D015221:Potassium Channels / Q000187:drug effects; D011651:Pulmonary Artery / Q000166:cytology; D051381:Rats; D017208:Rats, Wistar
D015221:Potassium Channels; D019806:Cromakalim