Effects of aging on shortening velocity and myosin isoform
composition in single human skeletal muscle cells.
Larsson, Lars, Xiaopeng Li, and Walter R. Frontera.
Departments of Clinical Neurophysiology and Neurology, Karolinska
Hospital, Stockholm, Sweden, and Department of Physical Medicine and
Rehabilitation,
APStracts 3:0295C, 1996.
Maximum velocity of unloaded shortening (V0) and maximum force
normalised to cross-sectional fiber area (specific tension) were
determined in 400 single quadriceps muscle cells of young (n=4, 25-31
years) and old (n=4, 73-81 years) men. Two of the old men were
physically very active and the subjects were divided into young
control (YC), old control (OC) and old physically active (OPA)
groups. The expression of type I, IIA, and IIB myosin heavy chains
(MyHCs) and essential and regulatory myosin light chains (MyLCs) was
determined by 6% and 12% SDS-PAGE. V0 was highly dependent on the
MyHC isoform composition and a gradient from slow to fast was
observed in the sequence I, I-IIA, IIA, IIAB and IIB MyHC cells. The
V0_s and specific tensions of type I and IIA MyHC fibers in the YC
group were significantly higher than those in the OC and OPA groups.
Thus, the present results provide evidence of qualitative changes in
contractile properties of human skeletal muscle in old age, which
probably play an important role in the age-related impairment of
skeletal muscle function.
Received 29 April 1996; accepted in final form 9 September 1996.
APS Manuscript Number C236-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 7 October 1996