Effects of reduced joint mobility and training on Na,K-ATPase and Ca-ATPase in skeletal muscle.
In guinea pigs, the ankle joint was partly immobilized in a position reducing dorsiflection to 105 degrees (as compared to the normal value of 30 degrees). When compared with the contralateral unrestrained leg, this led to a significant atrophy and a decrease in contractile force (-23%) of the gastrocnemius muscle. This was associated with a significant decrease in the total concentration of [3H]ouabain binding sites in gastrocnemius and plantaris muscle reaching minimum (-19% and -23%) after 3 weeks, but no evidence of degenerative changes. Total contents of Ca and Ca-ATPase were increased by 27% and 22%, respectively. After 4 to 5 weeks of reduced mobility, the concentration of [3H]ouabain binding sites in gastrocnemius muscle returned to control level. The lowest concentration of [3H]ouabain binding sites reached during reduced mobility was 258 +/- 13 pmol/g wet wt., and the maximum value attained following 3 weeks of reduced mobility and 3 weeks of training by running was 498 +/- 25 pmol/g wet wt., i.e, 93% higher. In soleus, training produced an increase of 25%. Clinically, it is important to realize that movable braces cannot prevent the development of muscular atrophy. The observed spontaneous recovery of the Na,K-pump concentration may partly explain why patients using movable casts show a better capacity for physical performance than those treated with complete immobilization. In conclusion, the total concentration of Na,K-pumps in guinea pig skeletal muscle undergoes downregulation and upregulation as a function of contractile activity as well as muscle length under conditions mimicking the constraints on mobility frequently used in the clinical treatment of lesions.
Leivseth
G
G
Department of Physiology, University of Tromsø, Norway.
Clausen
T
T
Everts
M E
ME
Bjordal
E
E
D000818:Animals; D000252:Calcium-Transporting ATPases / Q000032:analysis*; D005260:Female; D006168:Guinea Pigs; D006614:Hindlimb; D007103:Immobilization / Q000009:adverse effects*; D009132:Muscles / Q000201:enzymology* / Q000503:physiopathology; D010805:Physical Conditioning, Animal; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis*; D013997:Time Factors
D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase