Force-velocity and Power Characteristics of Rat Soleus Muscle Fibers after Hindlimb Suspension

Authors

Kerry S. McDonald, Marquette University
C. A. Blaser, Marquette University
Robert H. Fitts, Marquette UniversityFollow

Document Type

Article

Language

eng

Format of Original

8 p.

Publication Date

10-1994

Publisher

American Physiological Society

Source Publication

Journal of Applied Physiology

Source ISSN

0021-8987

Original Item ID

DOI: 10.1152/jappl.1994.77.4.1609

Abstract

The effects of 1, 2, and 3 wk of hindlimb suspension (HS) on force-velocity and power characteristics of single rat soleus fibers were determined. After 1, 2, or 3 wk of HS, small fiber bundles were isolated, placed in skinning solution, and stored at -20 degrees C until studied. Single fibers were isolated and placed between a motor arm and force transducer, functional properties were studied, and fiber protein content was subsequently analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Additional fibers were isolated from soleus of control and after 1 and 3 wk of HS, and fiber type distribution and myosin light chain stoichiometry were determined from SDS-PAGE analysis. After 1 wk of HS, percent type I fibers declined from 82 to 74%, whereas hybrid fibers increased from 10 to 18%. Percent fast type II fibers increased from 8% in control and 1 wk of HS to 26% by 3 wk of HS. Most fibers showed an increased unloaded maximal shortening velocity (V_o), but myosin heavy chain remained entirely slow type I. The mechanism for increased V_o is unknown. There was a progressive decrease in fiber diameter (14, 30, and 38%) and peak force (38, 56, and 63%) after 1, 2, and 3 wk of HS, respectively. One week of HS resulted in a shift of the force-velocity curve, and between 2 and 3 wk of HS the curve shifted further such that V_o was higher than control at all relative loads < 45% peak isometric force. Peak absolute power output of soleus fibers progressively decreased through 2 wk of HS but showed no further change at 3 wk. The results suggest that between 2 and 3 wk the HS-induced alterations in the force-velocity relationship act to maintain the power output of single soleus fibers despite a continued reduction in fiber force.

Comments

Journal of Applied Physiology, Vol. 77, No. 4 (October 1994): 1609-1616. DOI.

Recommended Citation

McDonald, Kerry S.; Blaser, C. A.; and Fitts, Robert H., "Force-velocity and Power Characteristics of Rat Soleus Muscle Fibers after Hindlimb Suspension" (1994). Biological Sciences Faculty Research and Publications. 459.
https://epublications.marquette.edu/bio_fac/459