TY - JOUR
T1 - Age-related changes in contractile properties of single skeletal fibers from the soleus muscle
AU - Thompson, Ladora V.
AU - Brown, Marybeth
PY - 1999/3
Y1 - 1999/3
N2 - Peak absolute force, specific tension (peak absolute force per cross- sectional area), cross-sectional area, maximal unloaded shortening velocity (V0; determined by the slack test), and myosin heavy chain (MHC) isoform compositions were determined in 124 single skeletal fibers from the soleus muscle of 12-, 24-, 30-, 36-, and 37-mo-old Fischer 344 Brown Norway F1 Hybrid rats. All fibers expressed the type I MHC isoform. The mean V0 remained unchanged from 12 to 24 mo but did decrease significantly from the 24- to 30-mo time period (from 1.71 ± 0.13 to 0.85 ± 0.09 fiber lengths/s). Fiber cross-sectional area remained constant until 36 mo of age, at which time there was a 20% decrease from the values at 12 mo of age (from 5,558 ± 232 to 4,339 ± 280 μm2). A significant decrease in peak absolute force of single fibers occurred between 12 and 24 mo of age (from 51 ± 2 x 10-5 to 35 ± 2 x 10-5 N) and then remained constant until 36 mo, when another 43% decrease occurred. Like peak absolute force, the specific tension decreased significantly between 12 and 24 mo by 20%, and another 32% decline was observed at 37 mo. Thus, by 24 mo, there was a dissociation between the loss of fiber cross-sectional area and force. The results suggest time-specific changes of the contractile properties with aging that are independent of each other. Underlying mechanisms responsible for the time-dependent and contractile property-specific changes are unknown. Age-related changes in the molecular dynamics of myosin may be the underlying mechanism for altered force production. The presence of more than one β/slow MHC isoform may be the mechanism for altered force production. The presence of more than one β/slow MHC isoform may be the mechanism for the altered V0 with age.
AB - Peak absolute force, specific tension (peak absolute force per cross- sectional area), cross-sectional area, maximal unloaded shortening velocity (V0; determined by the slack test), and myosin heavy chain (MHC) isoform compositions were determined in 124 single skeletal fibers from the soleus muscle of 12-, 24-, 30-, 36-, and 37-mo-old Fischer 344 Brown Norway F1 Hybrid rats. All fibers expressed the type I MHC isoform. The mean V0 remained unchanged from 12 to 24 mo but did decrease significantly from the 24- to 30-mo time period (from 1.71 ± 0.13 to 0.85 ± 0.09 fiber lengths/s). Fiber cross-sectional area remained constant until 36 mo of age, at which time there was a 20% decrease from the values at 12 mo of age (from 5,558 ± 232 to 4,339 ± 280 μm2). A significant decrease in peak absolute force of single fibers occurred between 12 and 24 mo of age (from 51 ± 2 x 10-5 to 35 ± 2 x 10-5 N) and then remained constant until 36 mo, when another 43% decrease occurred. Like peak absolute force, the specific tension decreased significantly between 12 and 24 mo by 20%, and another 32% decline was observed at 37 mo. Thus, by 24 mo, there was a dissociation between the loss of fiber cross-sectional area and force. The results suggest time-specific changes of the contractile properties with aging that are independent of each other. Underlying mechanisms responsible for the time-dependent and contractile property-specific changes are unknown. Age-related changes in the molecular dynamics of myosin may be the underlying mechanism for altered force production. The presence of more than one β/slow MHC isoform may be the mechanism for altered force production. The presence of more than one β/slow MHC isoform may be the mechanism for the altered V0 with age.
KW - Fiber diameter
KW - Maximal unloaded shortening velocity
KW - Myosin heavy chain
KW - Peak absolute force
KW - Specific tension
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U2 - 10.1152/jappl.1999.86.3.881
DO - 10.1152/jappl.1999.86.3.881
M3 - Article
C2 - 10066700
AN - SCOPUS:0033053614
SN - 8750-7587
VL - 86
SP - 881
EP - 886
JO - Journal of applied physiology
JF - Journal of applied physiology
IS - 3
ER -