Exercise effects on the size and metabolic properties of soleus fibers in hindlimb-suspended rats

S. C. Graham, R. R. Roy, S. P. West, Donald Thomason, K. M. Baldwin

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

The soleus atrophies rapidly when a rat is subjected to hindlimb suspension (HS), probably as a result of a decrease in the force encountered by the muscle. To test this premise, adult female rats were HS and half the rats were exercised (HS-EX) on a treadmill for 1.5 h·d -1 at 20 m·min -1 and a 30% grade. After 4 weeks, the midbelly of the soleus was prepared for histochemical analysis. Fibers were typed as dark or light staining for myosin ATPase, alkaline preincubation. Fiber size and quantitative histochemical enzyme activities of succinate dehydrogenase (SDH) were determined using a computer enhanced image processing system. In comparison to age-matched controls, the soleus wet weight was 69 and 30% smaller in HS and HS-EX rats. The mean cross sectional area of the dark ATPase fibers was reduced by 46 and 18% and light ATPase fibers by 69 and 48% in the HS and HS-EX, respectively. The percent dark ATPase fibers increased from 10% in the control rats to 19 and 17% in the HS and HS-EX. In both suspended groups, SDH activities in light ATPase fibers were 40% higher than control. The SDH activity of the dark ATPase fibers of HS-EX was 20% higher than control, while the dark ATPase fibers of HS were similar to control. To determine the degree to which these increases in SDH could be related to reductions in fiber size rather than increases in the actual amount of protein, integrated activity (activity/min x area) was calculated per fiber. The integrated activity of SDH suggests a net loss of this enzyme in the light and dark ATPase fibers of HS, but only in the light ATPase fibers of the HS-EX rats. In summary, daily treadmill exercise ameliorated, but did not prevent, the muscle fiber atrophy induced by HS in a slow extensor muscle. Further, SDH activity per fiber was maintained or elevated in the HS and HS-EX rats regardless of the variable changes in fiber size induced by suspension and endurance type exercise.

Original languageEnglish (US)
Pages (from-to)226-234
Number of pages9
JournalAviation Space and Environmental Medicine
Volume60
Issue number3
StatePublished - 1989
Externally publishedYes

Fingerprint

Hindlimb Suspension
Hindlimb
Rats
Fibers
Succinate Dehydrogenase
Adenosine Triphosphatases
Light
Muscle
Exercise equipment
Rat control
Muscles
Muscular Atrophy
Enzyme activity

All Science Journal Classification (ASJC) codes

  • Pollution
  • Medicine(all)
  • Public Health, Environmental and Occupational Health

Cite this

Exercise effects on the size and metabolic properties of soleus fibers in hindlimb-suspended rats. / Graham, S. C.; Roy, R. R.; West, S. P.; Thomason, Donald; Baldwin, K. M.

In: Aviation Space and Environmental Medicine, Vol. 60, No. 3, 1989, p. 226-234.

Research output: Contribution to journalArticle

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abstract = "The soleus atrophies rapidly when a rat is subjected to hindlimb suspension (HS), probably as a result of a decrease in the force encountered by the muscle. To test this premise, adult female rats were HS and half the rats were exercised (HS-EX) on a treadmill for 1.5 h·d -1 at 20 m·min -1 and a 30{\%} grade. After 4 weeks, the midbelly of the soleus was prepared for histochemical analysis. Fibers were typed as dark or light staining for myosin ATPase, alkaline preincubation. Fiber size and quantitative histochemical enzyme activities of succinate dehydrogenase (SDH) were determined using a computer enhanced image processing system. In comparison to age-matched controls, the soleus wet weight was 69 and 30{\%} smaller in HS and HS-EX rats. The mean cross sectional area of the dark ATPase fibers was reduced by 46 and 18{\%} and light ATPase fibers by 69 and 48{\%} in the HS and HS-EX, respectively. The percent dark ATPase fibers increased from 10{\%} in the control rats to 19 and 17{\%} in the HS and HS-EX. In both suspended groups, SDH activities in light ATPase fibers were 40{\%} higher than control. The SDH activity of the dark ATPase fibers of HS-EX was 20{\%} higher than control, while the dark ATPase fibers of HS were similar to control. To determine the degree to which these increases in SDH could be related to reductions in fiber size rather than increases in the actual amount of protein, integrated activity (activity/min x area) was calculated per fiber. The integrated activity of SDH suggests a net loss of this enzyme in the light and dark ATPase fibers of HS, but only in the light ATPase fibers of the HS-EX rats. In summary, daily treadmill exercise ameliorated, but did not prevent, the muscle fiber atrophy induced by HS in a slow extensor muscle. Further, SDH activity per fiber was maintained or elevated in the HS and HS-EX rats regardless of the variable changes in fiber size induced by suspension and endurance type exercise.",
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