K+ as a vasodilator in resting human muscle: implications for exercise hyperaemia

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Abstract:

Abstract Aim: 

Potassium (K+) released from contracting skeletal muscle is considered a vasodilatory agent. This concept is mainly based on experiments infusing non-physiological doses of K+. The aim of the present study was to investigate the role of K+ in blood flow regulation. Methods: 

We measured leg blood flow (LBF) and arterio-venous (A-V) O2 difference in 13 subjects while infusing K+ into the femoral artery at a rate of 0.2, 0.4, 0.6 and 0.8 mmol min−1. Results: 

The lowest dose increased the calculated femoral artery plasma K+ concentration by approx.1 mmol L−1. Graded K+ infusions increased LBF from 0.39 ± 0.06 to 0.56 ± 0.13, 0.58 ± 0.17, 0.61 ± 0.11 and 0.71 ± 0.17 L min−1, respectively, whereas the leg A-V O2 difference decreased from 74 ± 9 to 60 ± 12, 52 ± 11, 53 ± 9 and 45 ± 7 mL L−1, respectively (P < 0.05). Mean arterial pressure was unchanged, indicating that the increase in LBF was associated with vasodilatation. The effect of K+ was totally inhibited by infusion (27 mol min−1) of Ba2+, an inhibitor of Kir2.1 channels. Simultaneous infusion of ATP and K+ evoked an increase in LBF equalled to the sum of their effects. Conclusions: 

Physiological infusions of K+ induce significant increases in resting LBF, which are completely blunted by inhibition of the Kir2.1 channels. The present findings in resting skeletal muscle suggest that K+ released from contracting muscle might be involved in exercise hyperaemia. However, the magnitude of increase in LBF observed with K+ infusion suggests that K+ only accounts for a limited fraction of the hyperaemic response to exercise.

Keywords: channels; flow; potassium; regulation

Document Type: Research Article

DOI: http://dx.doi.org/10.1111/j.1748-1716.2007.01678.x

Affiliations: 1:  Institute of Molecular Biology and Physiology, Copenhagen Muscle Research Centre, University of Copenhagen, Copenhagen, Denmark 2:  Rigshospitalet, Copenhagen, Denmark

Publication date: August 1, 2007

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