Effect of hypokinesia-hypodynamia on rat muscle oxidative capacity and glucose uptake.
Whole-body hypokinetic-hypodynamic (H/H) suspension, unlike other models of muscle disuse, allows voluntary contractile activity. This study examined the oxidative capacity and insulin sensitivity of rat hindlimb muscles subjected to 7 days of suspension H/H conditions. Oxidative capacity was determined by measuring citrate synthase activity and cytochrome c concentration in soleus and gastrocnemius muscles. A perfused hindquarter preparation was used to measure glucose uptake rates at rest with physiological and supramaximal concentrations of insulin in the perfusate. Citrate synthase activity was 17% lower in soleus and 23% lower in gastrocnemius muscles from H/H rats. Similarly, a 29% decrease in H/H rat gastrocnemius cytochrome c concentration was observed. Rates of glucose uptake were lower in muscles from H/H rats compared with controls at physiological levels of insulin and did not increase in response to a further increase in insulin concentration. Muscles undergoing a significant loss in mass after 7 days suspension were found to have increased glycogen concentrations. In conclusion, data presented in this study suggest that hindlimb muscle disuse, brought about by whole-body suspension, results in a decreased aerobic capacity in load bearing muscles and a lowered insulin sensitivity in perfused rat hindlimb muscles.
D000818:Animals; D003574:Cytochrome c Group / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D006003:Glycogen / Q000378:metabolism; D006614:Hindlimb; D007328:Insulin / Q000494:pharmacology; D007773:Lactates / Q000378:metabolism; D008297:Male; D009132:Muscles / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism*; D009133:Muscular Atrophy / Q000378:metabolism*; D009929:Organ Size; D010101:Oxygen Consumption; D051381:Rats; D011919:Rats, Inbred Strains
D003574:Cytochrome c Group; D007328:Insulin; D007773:Lactates; D006003:Glycogen; D005947:Glucose