Adaptive potentials of skeletal muscle in young and aging rats.
We compared responses of the fast extensor digitorum longus (EDL) and tibialis anterior (TA) muscles in young (15-week) and aging (101-week) male Brown Norwegian rats to 50 days of chronic low-frequency stimulation (CLFS, 10 Hz, 10 hours/day). After 50 days of CLFS, the EDL muscles of the young (22-week) and aging (108-week) rats displayed similar increases in type IIA fibers, relative concentration of myosin heavy chain MHCIIa, elevations in mitochondrial citrate synthase and 3-hydroxyacyl-CoA dehydrogenase activities, and similar decreases in glycolytic enzyme activities (glyceraldehydephosphate dehydrogenase, lactate dehydrogenase). TA muscle in young rats contained a few cytochrome c oxidase negative (COX-) type I fibers. Their number was approximately 2-fold elevated by CLFS. Conversely, aging muscle, which contained a slightly higher amount of COX- fibers than young TA muscle, responded to CLFS with a significant decrease in COX- fibers. The appearance of small COX-positive type I fibers in stimulated aging muscle indicated that regenerating type I fibers "diluted" the COX-deficient fiber population.
Pette
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Department of Biology, University of Konstanz, Germany.
Skorjanc
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D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000378:metabolism; D000222:Adaptation, Physiological / Q000502:physiology*; D000375:Aging / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D002950:Citrate (si)-Synthase / Q000378:metabolism; D004558:Electric Stimulation; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000201:enzymology / Q000502:physiology*; D018482:Muscle, Skeletal / Q000201:enzymology / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000378:metabolism; D010084:Oxidation-Reduction; D051381:Rats; D011914:Rats, Inbred BN
D015094:3-Hydroxyacyl CoA Dehydrogenases; D007770:L-Lactate Dehydrogenase; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D002950:Citrate (si)-Synthase; D018995:Myosin Heavy Chains