Faculty Collaboration Database

Fiber-type susceptibility to eccentric contraction-induced damage of hindlimb-unloaded rat AL muscles. J Appl Physiol (1985) 2001 Mar;90(3):770-6

Date

02/22/2001

Pubmed ID

11181582

DOI

10.1152/jappl.2001.90.3.770

Scopus ID

2-s2.0-0035105723 (requires institutional sign-in at Scopus site)   94 Citations

Abstract

Slow oxidative (SO) fibers of the adductor longus (AL) were predominantly damaged during voluntary reloading of hindlimb unloaded (HU) rats and appeared explainable by preferential SO fiber recruitment. The present study assessed damage after eliminating the variable of voluntary recruitment by tetanically activating all fibers in situ through the motor nerve while applying eccentric (lengthening) or isometric contractions. Muscles were aldehyde fixed and resin embedded, and semithin sections were cut. Sarcomere lesions were quantified in toluidine blue-stained sections. Fibers were typed in serial sections immunostained with antifast myosin and antitotal myosin (which highlights slow fibers). Both isometric and eccentric paradigms caused fatigue. Lesions occurred only in eccentrically contracted control and HU muscles. Fatigue did not cause lesions. HU increased damage because lesioned- fiber percentages within fiber types and lesion sizes were greater than control. Fast oxidative glycolytic (FOG) fibers were predominantly damaged. In no case did damaged SO fibers predominate. Thus, when FOG, SO, and hybrid fibers are actively lengthened in chronically unloaded muscle, FOG fibers are intrinsically more susceptible to damage than SO fibers. Damaged hybrid-fiber proportions ranged between these extremes.

Author List

Vijayan K, Thompson JL, Norenberg KM, Fitts RH, Riley DA

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
Hindlimb
Isometric Contraction
Male
Motor Neurons
Muscle Contraction
Muscle Fatigue
Muscle Fibers, Skeletal
Muscle Fibers, Slow-Twitch
Muscle, Skeletal
Rats
Rats, Sprague-Dawley
Sarcomeres
Time Factors