title: Cardiac and skeletal muscle adaptations to voluntary wheel running in the mouse.
abstract: In this paper, we describe the effects of voluntary cage wheel exercise on mouse cardiac and skeletal muscle. Inbred male C57/Bl6 mice (age 6-8 wk; n = 12) [corrected] ran an average of 4.3 h/24 h, for an average distance of 6.8 km/24 h, and at an average speed of 26.4 m/min. A significant increase in the ratio of heart mass to body mass (mg/g) was evident after 2 wk of voluntary exercise, and cardiac atrial natriuretic factor and brain natriuretic peptide mRNA levels were significantly increased in the ventricles after 4 wk of voluntary exercise. A significant increase in the percentage of fibers expressing myosin heavy chain (MHC) IIa was observed in both the gastrocnemius and the tibialis anterior (TA) by 2 wk, and a significant decrease in the percentage of fibers expressing IIb MHC was evident in both muscles after 4 wk of voluntary exercise. The TA muscle showed a greater increase in the percentage of IIa MHC-expressing fibers than did the gastrocnemius muscle (40 and 20%, respectively, compared with 10% for nonexercised). Finally, the number of oxidative fibers as revealed by NADH-tetrazolium reductase histochemical staining was increased in the TA but not the gastrocnemius after 4 wk of voluntary exercise. All results are relative to age-matched mice housed without access to running wheels. Together these data demonstrate that voluntary exercise in mice results in cardiac and skeletal muscle adaptations consistent with endurance exercise.
authors: Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder 80309-0347, USA.
authors: D L
authors: DL
authors: Allen
authors: B C
authors: BC
authors: Harrison
authors: A
authors: A
authors: Maass
authors: M L
authors: ML
authors: Bell
authors: W C
authors: WC
authors: Byrnes
authors: L A
authors: LA
authors: Leinwand
mesh_terms: D000064:Acclimatization; D000818:Animals; D001835:Body Weight; D006321:Heart / Q000033:anatomy & histology / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009043:Motor Activity / Q000502:physiology*; D018656:Muscle Fibers, Fast-Twitch / Q000166:cytology / Q000502:physiology; D018657:Muscle Fibers, Slow-Twitch / Q000166:cytology / Q000502:physiology; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000032:analysis; D009246:NADH Tetrazolium Reductase / Q000032:analysis; D009929:Organ Size; D010805:Physical Conditioning, Animal / Q000502:physiology*
chemical_list: D009246:NADH Tetrazolium Reductase; D018995:Myosin Heavy Chains