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K + as a vasodilator in resting human muscle: implications for exercise hyperaemia
Author(s) -
Juel C.,
Olsen S.,
Rentsch R. L.,
GonzálezAlonso J.,
Rosenmeier J. B.
Publication year - 2007
Publication title -
acta physiologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.591
H-Index - 116
eISSN - 1748-1716
pISSN - 1748-1708
DOI - 10.1111/j.1748-1716.2007.01678.x
Subject(s) - hyperaemia , vasodilation , femoral artery , skeletal muscle , medicine , endocrinology , chemistry , blood flow , artery , potassium , organic chemistry
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) O 2 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 O 2 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 μ mol min −1 ) of Ba 2+ , 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.