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Journal of Applied Physiology, Vol 74, Issue 5 2072-2078, Copyright © 1993 by American Physiological Society
ARTICLES |
C. S. Stump, C. R. Woodman, R. F. Fregosi and C. M. Tipton
Department of Exercise and Sport Sciences, School of Health Related Professions, University of Arizona, Tucson 85721.
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)
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C. S. Stump, C. M. Tipton, and E. J. Henriksen Muscle adaptations to hindlimb suspension in mature and old Fischer 344 rats J Appl Physiol, June 1, 1997; 82(6): 1875 - 1881. [Abstract] [Full Text] [PDF] |
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