Faculty Collaboration Database

Models of disuse: a comparison of hindlimb suspension and immobilization. J Appl Physiol (1985) 1986 Jun;60(6):1946-53

Date

06/01/1986

Pubmed ID

3722061

DOI

10.1152/jappl.1986.60.6.1946

Scopus ID

2-s2.0-0022476925 (requires institutional sign-in at Scopus site)   164 Citations

Abstract

The effects of 1 and 2 wk of hindlimb suspension (HS) on rat skeletal muscle function were determined and the results compared with those obtained previously with hindlimb immobilization (HI). Both models of disuse (HS and HI) primarily affected slow-twitch muscle. Each decreased the isometric twitch duration in the slow-twitch soleus; however, the HS-mediated effect was entirely a result of a shortened contraction time (CT), whereas HI reduced one-half relaxation time (1/2 RT) as well as CT. Soleus muscle mass and peak tetanic tension (Po) declined with disuse. The HS effect on muscle mass and Po was variable, however, for all experiments HS produced atrophy equal to or greater than HI. A major difference existed in the effects of HS and HI on the maximal speed of soleus muscle shortening (Vmax). One and 2 wk of HS produced increases in Vmax to 4.45 +/- 0.34 and 6.83 +/- 0.74 fiber lengths/s, respectively, compared with control velocities of 3.05 +/- 0.08. By contrast over a similar time period, HI had no significant effect on soleus Vmax. The increase in Vmax at 14 days of HS was associated with, and perhaps caused by, the increased expression of a second faster migrating isozyme of myosin. The new native isozyme comigrated with fast myosin, but its light chain subunits contained only LC1s and LC2s. The mechanism responsible for the increase is unknown. One plausible explanation is that the apparent HS-mediated modification in muscle fiber type is dependent on the elimination of loadbearing or isometric contractions, a condition that does not exist during HI.

Author List

Fitts RH, Metzger JM, Riley DA, Unsworth BR

Author

Robert Fitts PhD Professor in the Biological Sciences department at Marquette University

MESH terms used to index this publication - Major topics in bold

Animals
Contractile Proteins
Disease Models, Animal
Electrophoresis
Hindlimb
Immobilization
Isometric Contraction
Male
Movement Disorders
Muscle Contraction
Muscular Atrophy
Myosins
Rats
Rats, Inbred Strains
Restraint, Physical
Time Factors
Weightlessness