Aging does not attenuate plantaris muscle hypertrophy in male Fischer 344 rats.
OBJECTIVE
The present study examined the effect of extreme old age on the plasticity of the rat plantaris muscle in response to an increase in mechanical load.


METHODS
Male Fischer 344 rats, aged 7 months (adult) and 25 months (old) underwent bilateral surgical ablation of the gastrocnemius muscle to functionally overload (OV) the fast-twitch plantaris muscle for 8 wk


RESULTS
At 27 months of age, plantaris wet weight and cross-sectional area (CSA) were unaffected by age, but aging decreased peak isometric tension (Po) 27% (P < 0.05). Plantaris muscle myosin heavy chain composition indicated a loss of faster myosin heavy chains (MHC) isoforms with concomitant increases in slower MHC in old rats (P < 0.05). In adult rats, OV increased muscle CSA and Po 72% and 83%, respectively (P < 0.05). Similarly, OV increased CSA and Po 69% and 73%, respectively, in old rats (P < 0.05). Average fiber CSA increased 57% and 68% in adult-OV and old-OV rats, respectively (P < 0.05).


CONCLUSIONS
Collectively, our data indicate that plantaris muscle mass and plasticity in response to increased mechanical load are well conserved in very aged male Fischer 344 rats.
The Laboratory of Basic and Applied Myology, Department of Physical Activity and Educational Services, The Ohio State University, Columbus, OH, USA. jonlinderman@udayton.edu
Jon K
JK
Linderman
Eric R
ER
Blough
D000375:Aging / Q000502:physiology*; D000818:Animals; D001696:Biomechanical Phenomena; D004548:Elasticity; D006984:Hypertrophy / Q000503:physiopathology; D007091:Image Processing, Computer-Assisted; D007537:Isometric Contraction / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000473:pathology; D018482:Muscle, Skeletal / Q000473:pathology* / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000032:analysis*; D051381:Rats; D011916:Rats, Inbred F344
D018995:Myosin Heavy Chains