Exercise-induced regulation of muscular N+-K+ pump, FXYD1, and NHE1 mRNA and protein expression: importance of training status, intensity, and muscle type

Rasmussen MK, Juel C, Nordsborg NB. Exercise-induced regulation of muscular Na+-K+ pump, FXYD1, and NHE1 mRNA and protein expression: importance of training status, intensity, and muscle type. Am J Physiol Regul Integr Comp Physiol 300: R1209-R1220, 2011. First published February 16, 2011; doi:10.1152/ajpregu.00635.2010.-It is investigated if exercise-induced mRNA changes cause similar protein expression changes of Na+-K+ pump isoforms (alpha(1), alpha(2), beta(1), beta(2)), FXYD1, and Na+/K+ exchanger (NHE1) in rat skeletal muscle. Expression was evaluated (n = 8 per group) in soleus and extensor digutorum longus after 1 day, 3 days, and 3 wk (5 sessions/wk) of either sprint (4 x 3-min sprint + 1-min rest) or endurance (20 min) running. Two hours after exercise on day 1, no change in protein expression was apparent in either training group or muscle, whereas sprint exercise increased the mRNA of soleus alpha(2) (4.9 +/- 0.8-fold; P < 0.05), beta(2) (13.2 +/- 4.4-fold; P < 0.001), and NHE1 (12.0 +/- 3.1-fold; P < 0.01). Two hours after sprint exercise, protein expression normalized to control samples was higher on day 3 than day 1 for soleus alpha(1) (41 +/- 18% increase vs. 15 +/- 8% reduction; P < 0.05), alpha(2) (64 +/- 35% increase vs. 37 +/- 12% reduction; P < 0.05), beta(1) (17 +/- 21% increase vs. 14 +/- 29% reduction; P < 0.05), and FXYD1 (35 +/- 16% increase vs. 13 +/- 10% reduction; P < 0.05). In contrast, on day 3, soleus alpha(1) (0.1 +/- 0.1-fold; P < 0.001), alpha(2) (0.2 +/- 0.1-fold; P < 0.001), beta(1) (0.4 +/- 0.1-fold; P < 0.05), and beta(2)-mRNA (2.9 +/- 1.7-fold; P < 0.001) expression was lower than after exercise on day 1. After 3 wk of training, no change in protein expression relative to control existed. In conclusion, increased expression of Na+-K+ pump subunits, FXYD1 and NHE1 after 3 days exercise training does not appear to be an effect of increased constitutive mRNA levels. Importantly, sprint exercise can reduce mRNA expression concomitant with increased protein expression.