Muscle Na
-K
-ATPase activity and isoform adaptations

shiliangyin

From R. J. Aughey,1 K. T. Murphy,1 S. A. Clark,2 A. P. Garnham,3 R. J. Snow,3 D. Cameron-Smith,3 J. A. Hawley,2 and M. J. McKenna1
Aughey RJ, Murphy KT, Clark SA, Garnham AP, Snow
RJ, Cameron-Smith D, Hawley JA, McKenna MJ. Muscle
Na
-K
-ATPase activity and isoform adaptations to intense
interval exercise and training in well-trained athletes. J Appl
Physiol 103: 39–47, 2007. First published April 19, 2007;
doi:10.1152/japplphysiol.00236.2006.—The Na
-K
-ATPase enzyme
is vital in skeletal muscle function. We investigated the effects
of acute high-intensity interval exercise, before and following highintensity
training (HIT), on muscle Na
-K
-ATPase maximal activity,
content, and isoform mRNA expression and protein abundance.
Twelve endurance-trained athletes were tested at baseline, pretrain,
and after 3 wk of HIT (posttrain), which comprised seven sessions of
8  5-min interval cycling at 80% peak power output. Vastus lateralis
muscle was biopsied at rest (baseline) and both at rest and immediately
postexercise during the first (pretrain) and seventh (posttrain)
training sessions. Muscle was analyzed for Na
-K
-ATPase maximal
activity (3-O-MFPase), content ([3H]ouabain binding), isoform
mRNA expression (RT-PCR), and protein abundance (Western blotting).
All baseline-to-pretrain measures were stable. Pretrain, acute
exercise decreased 3-O-MFPase activity [12.7% (SD 5.1), P  0.05],
increased 1, 2, and 3 mRNA expression (1.4-, 2.8-, and 3.4-fold,
respectively, P  0.05) with unchanged -isoform mRNA or protein
abundance of any isoform. In resting muscle, HIT increased (P 
0.05) 3-O-MFPase activity by 5.5% (SD 2.9), and 3 and 3 mRNA
expression by 3.0- and 0.5-fold, respectively, with unchanged Na
-
K
-ATPase content or isoform protein abundance. Posttrain, the
acute exercise induced decline in 3-O-MFPase activity and increase in
1 and 3 mRNA each persisted (P  0.05); the postexercise
3-O-MFPase activity was also higher after HIT (P  0.05). Thus HIT
augmented Na
-K
-ATPase maximal activity despite unchanged
total content and isoform protein abundance. Elevated Na
-K
-
ATPase activity postexercise may contribute to reduced fatigue after
training. The Na
-K
-ATPase mRNA response to interval exercise
of increased - but not -mRNA was largely preserve posttrain,
suggesting a functional role of  mRNA upregulation.