NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Effect of Hindlimb Unweighting on Single Soleus Fiber Maximal Shortening Velocity and ATPase ActivityThis study characterizes the time course of change in single soleus muscle fiber size and function elicited by hindlimb un weighting (HU) and analyzes the extent to which varying durations of HU altered maximal velocity of shortening (V(sub o)), myofibrillar adenosinetriphosphatase (ATPase), and relative content of slow and fast myosin in individual soleus fibers. After 1, 2, or 3 weeks of HU, soleus muscle bundles were prepared and stored in skinning solution at -20 C. Single fibers were isolated and mounted between a motor arm and a transducer, and fiber force, V(sub o), and ATPase activity were measured. Fiber myosin content was determined by one-dimensional sodium dodecyl sulfate- (SDS) polyacrylamide gel electrophoresis. After 1, 2, and 3 weeks of HU, soleus fibers exhibited a progressive reduction in fiber diameter (16, 22, and 42%, respectively) and peak force (42, 48, and 7%, respectively). Peak specific tension was significantly reduced after 1 week of HU (18%) and showed no further change in 2-3 weeks of HU. During 1 and 3 wk of HU, fiber V(sub o) and ATPase showed a significant increase. By 3 week, V(sub o) had increased from 1.32 +/- 0.04 to 2.94 +/- 0.17 fiber lengths/s and fiber ATPase from 291 +/- 16 to 1064 +/- 128 micro-M min(sub -1) mm(sub -3). The percent fibers expressing fast myosin heavy chain increased from 4% to 29% by 3 week of HU, and V(sub o) and ATPase activity within a fiber were highly correlated. However, a large population of fibers after 1, 2, and 3 weeks of HU showed increases in V(sub o) and ATPase but displayed the same myosin protein profile on SDS gels as control fibers. The mechanism eliciting increased fiber V(sub o) and ATPase activity was not obvious but may have been due to increases in fast myosin that went undetected on SDS gels and/or other factors unrelated to the myosin filament.
Document ID
19980007899
Acquisition Source
Ames Research Center
Document Type
Reprint (Version printed in journal)
Authors
McDonald, K. S.
(Marquette Univ. Milwaukee, WI United States)
Fitts, R. H.
(Marquette Univ. Milwaukee, WI United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1993
Publication Information
Publisher: American Physiological Society
ISSN: 0161-7567
Subject Category
Life Sciences (General)
Report/Patent Number
NAS 1.26:204848
NASA-CR-204848
Funding Number(s)
CONTRACT_GRANT: NAG2-212
Distribution Limits
Public
Copyright
Public Use Permitted.
No Preview Available