Exercise training increases inwardly rectifying K+ current and augments K+-mediated vasodilatation in deep femoral artery of rats

• Published in: Cardiovascular research Vol. 91; no. 1; pp. 142 - 150
• Main Authors: Jin, Chun Zi, Kim, Hyang Sun, Seo, Eun Yeong, Shin, Dong Hoon, Park, Kyung Sun, Chun, Yang-Sook, Zhang, Yin Hua, Kim, Sung Joon
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.07.2011
• Subjects: Animals; Biological and medical sciences; Cardiology. Vascular system; Cerebral Arteries - metabolism; Cerebral Arteries - physiopathology; Cerebrovascular Circulation; Femoral Artery - metabolism; Femoral Artery - physiopathology; Hyperemia - metabolism; Hyperemia - physiopathology; Ion Channel Gating; Male; Medical sciences; Membrane Potentials; Mesenteric Arteries - metabolism; Mesenteric Arteries - physiopathology; Microscopy, Video; Muscle, Skeletal - blood supply; Muscle, Smooth, Vascular - metabolism; Muscle, Smooth, Vascular - physiopathology; Myocytes, Smooth Muscle - metabolism; Physical Exertion; Potassium - metabolism; Potassium Channels, Inwardly Rectifying - metabolism; Rats; Rats, Sprague-Dawley; Regional Blood Flow; Sodium - metabolism; Splanchnic Circulation; Time Factors; Up-Regulation; Vasodilation; channel; Smooth muscle; Skeletal artery; Exercise training; Inwardly rectifying K; Physical exercise; Rat; Rodentia; Increase; Ionic channel; Phlebology; Vasodilation; Vertebrata; Mammalia; Animal; Exercise tolerance test; Deep femoral artery; Circulatory system; Cardiology; Current
• ISSN: 0008-6363; 1755-3245
• DOI: 10.1093/cvr/cvr050

Aims A moderate increase in extracellular [K+] ([K+]e) induces relaxation of small arteries by activating inwardly rectifying K+ current (I Kir). The K+-induced vasodilatation is an important mechanism for exercise-induced hyperaemia in skeletal muscle. We investigated whether I Kir and K+-induced vasodilatation are enhanced in deep femoral arteries (DFAs) from exercise-trained rats (ET rats; treadmill running for 20 min at 20 m/min, 3days/week for 2weeks). The effects of exercise training on K+-induced vasodilatation and I Kir were also investigated in cerebral (CA) and mesenteric arteries. Methods and results The K+-induced vasodilatation of DFAs and the density of I Kir and voltage-gated K+ current (I Kv) were increased in DFA myocytes of ET rats. The myogenic tone of the DFA was unchanged by exercise. Although similar functional up-regulations of I Kir and I Kv were observed in CA myocytes, the K+-induced vasodilatation was not increased in the CA of ET rats. Interestingly, concomitant to the increases in I Kir and I Kv, background Na+ conductance was also increased in the CA myocytes. However, such an effect was not observed in DFA myocytes from ET rats. Neither I Kir nor K+-induced vasodilatation was observed in mesenteric arteries of ET rats. Conclusion The present study provides evidence that regular exercise up-regulates I Kir in DFA and CA myocytes. Although the increase in I Kir was observed in two types of arteries, augmentation of K+-induced relaxation was observed only in the DFA of ET rats, possibly due to the increased Na+ conductance in CA myocytes. The increases in I Kir and K+-induced vasodilatation of the arteries of skeletal muscle suggest novel mechanisms of improved exercise hyperaemia with physical training.