Two-week inhalation of budesonide increases muscle Na,K ATPase content but not endurance in response to terbutaline in men.

While chronic systemic administration of glucocorticoids increases muscle Na ,K ATPase content, such effect is unexplored after therapeutic inhalation. We investigated the effect of therapeutic inhalation of the glucocorticoid budesonide on Na ,K ATPase content of skeletal muscle in men. Ten healthy trained subjects, aged 23 ± 4 years (mean ± 95% CI), participated in the study. Before and after 2 weeks of daily inhalation of budesonide (1.6 mg/day), a biopsy was taken from the vastus lateralis muscle for measurement of Na ,K ATPase content and blood samples were drawn for determination of plasma budesonide, cortisol, and K . Subjects' performance during cycling to fatigue at 90% of incremental peak power output (iPPO) was measured in response to 4 mg inhaled terbutaline to maximally stimulate Na ,K ATPase activity. Plasma concentrations of budesonide rose to 5.0 ± 1.6 nM with the intervention, whereas no changes were observed in plasma cortisol. Muscle Na ,K ATPase content increased (P ≤ 0.01) by 46 ± 34 pmol/(g wet wt) (17% increase) with the intervention. Cycling performance at 90% of iPPO did not change (P = 0.21) with the intervention (203 vs 214 s) in response to terbutaline. The present observations show that therapeutic inhalation of glucocorticoids increases muscle Na ,K ATPase content, but does not enhance high-intensity cycling endurance in response to terbutaline.

© 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.