Abstract
The putative effect of moderate training on human skeletal muscle Na,K-ATPase concentration
and thus on the capacity for active uptake of potassium was evaluated. In 15 conscripts
the Na,K-pump concentration was determined in vastus lateralis muscle by measurement
of 3 H-ouabain binding to intact muscle biopsies before and after 10 weeks of physical
training. All subjects had improved physical fitness, body weight was reduced by 3%
(P < 0.001), Cooper's test showed an improvement by 7% (P < 0.05) and leg circumference
10 cm above the knee joint had increased by 3% (P < 0.001). Mean Na,K-pump concentration
± S. E. M. in vastus lateralis muscles was 308±13 (N=15) and 300 ± 7 (N=15) pmol ×
g wet wt. -1 (P < 0.60) before and after training, respectively. Thus, in human subjects moderate
improvement of physical performance may occur without any change in skeletal muscle
Na,K-pump concentration. It may be, however, that change in the acute regulation of
skeletal muscle Na,K-ATPase - i. e.augmented activity of existing Na,K-pumps - may
reduce exercise-induced rise in plasma potassium concentration after moderate physical
conditioning. Since the circumference of the legs had increased, the total amount
of Na,K-ATPase in the legs had probably increased. Hence, moderate training may induce
muscle hypertrophy with a balanced synthesis of muscle mass and Na,K-pumps.
Key words
Na,K-ATPase - Na,K-pumps -
3 H-ouabain binding - cardiac glycoside receptors - skeletal muscle - training
