Muscle glucose uptake in the rat after suspension with single hindlimb weight bearing.
This study was designed to examine the effect of non-weight-bearing conditions and the systemic influences of simulated microgravity on rat hindlimb muscles. For this purpose, rats were suspended (SUS) in a head-down position (45 degrees) with the left hindlimb non-weight bearing (NWB) and the right hindlimb bearing 20% of presuspension body mass (WB). Weight bearing by the SUS-WB limb was accomplished by using a platform connected to a rod in sleeve, cable, and pulley apparatus to which weight could be added. Rats (250-325 g) were assigned to SUS or cage control (CC) conditions for 14 days. The angle between the foot and leg for SUS-WB and CC remained similar (20-30 degrees) throughout the experiment while the SUS-NWB hindlimbs extended to approximately 140 degrees by day 12. On day 14, the soleus, plantaris, and gastrocnemius muscles from the SUS-NWB limbs exhibited significantly lower (P < or = 0.05) masses than presuspension mass values (29, 11, and 21%, respectively). Weight bearing by the SUS-WB limbs prevented the loss of mass by these muscles. In separate groups of SUS and CC rats, 2-deoxyglucose uptake during hindlimb perfusion was significantly higher in both SUS-NWB and SUS-WB hindlimbs at 24,000 microU/ml of insulin compared with CC for all the muscles examined (21-80%). In addition, extracellular space (ml/g) was significantly greater in the soleus muscles from both the SUS-NWB and SUS-WB hindlimbs (64%) compared with CC muscles.(ABSTRACT TRUNCATED AT 250 WORDS)
Stump
C S
CS
Department of Exercise and Sport Sciences, School of Health Related Professions, University of Arizona, Tucson 85721.
Woodman
C R
CR
Fregosi
R F
RF
Tipton
C M
CM
D000818:Animals; D001284:Atrophy; D001835:Body Weight / Q000502:physiology; D003847:Deoxyglucose / Q000378:metabolism; D004576:Electromyography; D005110:Extracellular Space / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D006003:Glycogen / Q000378:metabolism; D006614:Hindlimb / Q000098:blood supply / Q000473:pathology / Q000502:physiology*; D007328:Insulin / Q000494:pharmacology; D008297:Male; D009132:Muscles / Q000098:blood supply / Q000378:metabolism* / Q000473:pathology; D009929:Organ Size / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow / Q000502:physiology; D014893:Weightlessness / Q000009:adverse effects*
D007328:Insulin; D006003:Glycogen; D003847:Deoxyglucose; D005947:Glucose