Dj. Duncker et al., Role of K-ATP(+) channels in regulation of systemic, pulmonary, and coronary vasomotor tone in exercising swine, AM J P-HEAR, 280(1), 2001, pp. H22-H33
Citations number
33
Categorie Soggetti
Cardiovascular & Hematology Research
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
The role of ATP-sensitive K+ (K-ATP(+)) channels in vasomotor tone regulati
on during metabolic stimulation is incompletely understood. Consequently, w
e studied the contribution of K-ATP(+) channels to vasomotor tone regulatio
n in the systemic, pulmonary, and coronary vascular bed in nine treadmill-e
xercising swine. Exercise up to 85% of maximum heart rate increased body O-
2 consumption fourfold, accommodated by a doubling of both cardiac output a
nd body O-2 extraction. Mean aortic pressure was unchanged, implying that s
ystemic vascular conductance (SVC) also doubled, whereas pulmonary artery p
ressure increased almost in parallel with cardiac output, so that pulmonary
vascular conductance (PVC) increased only 25 +/- 9% (both P< 0.05). Myocar
dial O-2 consumption tripled during exercise, which was paralleled by an eq
uivalent increase in O-2 supply so that coronary venous PO2 was maintained.
Selective K-ATP(+) channel blockade with glibenclamide (3 mg/kg iv), decre
ased SVC by 29 +/- 4% at rest and by 10 +/- 2% at 5 km/ h (both P< 0.05), w
hereas PVC was unchanged. Glibenclamide decreased coronary vascular conduct
ance and hence myocardial O-2 delivery, necessitating an increase in O-2 ex
traction from 76 +/- 2% to 86 +/- 2% at rest and from 79 +/- 2% to 83 +/- 1
% at 5 km/h. Consequently, coronary venous PO2 decreased from 25 +/- 1 to 1
7 +/- 1 mmHg at rest and from 23 +/- 1 to 20 +/- 1 mmHg at 5 km/h (all valu
es are P< 0.05). In conclusion, K-ATP(+) channels dilate the systemic and c
oronary, but not the pulmonary, resistance vessels at rest and during exerc
ise in swine. However, opening of K-ATP(+) channels is not mandatory for th
e exercise-induced systemic and coronary vasodilation.