Resistance training upregulates skeletal muscle Na+, K+-ATPase content, with elevations in both α1 and α2, but not β isoforms

Purpose
The Na+, K+-ATPase (NKA) is important in regulating trans-membrane ion gradients, cellular excitability and muscle function. We investigated the effects of resistance training in healthy young adults on the adaptability of NKA content and of the specific α and β isoforms in human skeletal muscle.

Methods
Twenty-one healthy young males (22.9 ± 4.6 year; 1.80 ± 0.70 m, 85.1 ± 17.8 kg, mean ± SD) underwent 7 weeks of resistance training, training three times per week (RT, n = 16) or control (CON, n = 5). The training program was effective with a 39% gain in leg press muscle strength (p = 0.001). A resting vastus lateralis muscle biopsy was taken before and following RT or CON and assayed for NKA content ([3H]ouabain binding site content) and NKA isoform (α1, α2, β1, β2) abundances.

Results
After RT, each of NKA content (12%, 311 ± 76 vs 349 ± 76 pmol g wet weight−1, p = 0.01), NKA α1 (32%, p = 0.01) and α2 (10%, p < 0.01) isoforms were increased, whereas β1 (p = 0.18) and β2 (p = 0.22) isoforms were unchanged. NKA content and isoform abundances were unchanged during CON.

Conclusions
Resistance training increased muscle NKA content through upregulation of both α1 and α2 isoforms, which were independent of β isoform changes. In animal models, modulations in α1 and α2 isoform abundances in skeletal muscle may affect fatigue resistance during exercise, muscle hypertrophy and strength. Whether similar in-vivo functional benefits of these NKA isoform adaptations occurs in human muscle with resistance training remains to be determined.