AJP - Cell Physiology, Vol 258, Issue 6 C1031-C1035, Copyright © 1990 by American Physiological Society
Aging does not affect contractile properties of type IIb FDL muscle in Fischer 344 rats
T. J. Walters, H. L. Sweeney and R. P. Farrar
Department of Kinesiology, University of Texas, Austin 78712.
The purpose of this study was to examine the influence of aging on the
contractile, metabolic, and histochemical properties of the predominantly
fast-twitch flexor digitorum longus muscle (FDL) in the Fischer 344 (F344)
rat strain. Contractile measurements were made in situ by stimulating the
motoneuron while the animals were under pentobarbital sodium anesthesia.
Fiber-type composition, capillarity, aerobic capacity, and myosin light
chain composition were also examined. The results of this investigation
were striking in that there was no alteration in any parameter measured.
Collectively, these results suggest that aging does not induce a functional
alteration in the neuromuscular relationship in the predominantly
fast-twitch FDL of F344 rats, and consequently, there is no loss of
functional capacity of the muscle. This study demonstrates that alteration
in predominantly fast-twitch muscle is not a universal phenomenon and that
care must be taken when generalizing about the influence of aging on
skeletal muscle. Some of the conflicting results regarding the influence of
aging on predominantly fast-twitch muscle in rodents may be either strain
or muscle specific.
