Faculty Collaboration Database

Shortening velocity and ATPase activity of rat skeletal muscle fibers: effects of endurance exercise training. Am J Physiol 1994 Jun;266(6 Pt 1):C1699-1713

Date

06/01/1994

Pubmed ID

8023900

DOI

10.1152/ajpcell.1994.266.6.C1699

Scopus ID

2-s2.0-0028356848 (requires institutional sign-in at Scopus site)   79 Citations

Abstract

Mechanical properties were measured in single skinned fibers from rat hindlimb muscle to test the hypothesis that the fast type IIb fiber exhibits a higher maximal shortening velocity (Vo) than the fast type IIa fiber and that the difference is directly attributable to a higher myofibrillar adenosinetriphosphatase (ATPase) activity in the type IIb fiber. Additional measurements were made to test the hypotheses that regular endurance exercise increases and decreases the Vo of the type I and IIa fiber, respectively, and that the altered Vo is associated with a corresponding change in the fiber ATPase activity. Rats were exercised by 8-12 wk of treadmill running for 2 h/day, 5 day/wk, up a 15% grade at a speed of 27 m/min. Fiber Vo was determined by the slack test, and the ATPase was measured fluorometrically in the same fiber. The myosin isozyme profile of each fiber was subsequently determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The mean +/- SE Vo (7.9 +/- 0.22 fiber lengths/s) of the type IIb fiber was significantly greater than the type IIa fiber (4.4 +/- 0.21 fiber lengths/s), and the higher Vo was associated with a higher ATPase activity (927 +/- 70 vs. 760 +/- 60 microM.min-1.mm-3). The exercise program induced cardiac hypertrophy and an approximately twofold increase in the mitochondrial marker enzyme citrate synthase. Exercise had no effect on fiber diameter or peak tension per cross-sectional area in any fiber type, but, importantly, it significantly increased (23%) both the Vo and the ATPase activity of the slow type I fiber of the soleus.(ABSTRACT TRUNCATED AT 250 WORDS)

Author List

Schluter JM, Fitts RH

Author

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

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

Adaptation, Physiological
Adenosine Triphosphatases
Animals
Male
Muscle Contraction
Muscles
Myosins
Physical Endurance
Physical Exertion
Rats
Rats, Sprague-Dawley
Time Factors