title: Changes in actomyosin ATP consumption rate in rat diaphragm muscle fibers during postnatal development.
abstract: Early postnatal development of rat diaphragm muscle (Dia(m)) is marked by dramatic transitions in myosin heavy chain (MHC) isoform expression. We hypothesized that the transition from the neonatal isoform of MHC (MHC(Neo)) to adult fast MHC isoform expression in Dia(m) fibers is accompanied by an increase in both the maximum velocity of the actomyosin ATPase reaction (V(max) ATPase) and the ATP consumption rate during maximum isometric activation (ATP(iso)). Rat Dia(m) fibers were evaluated at postnatal days 0, 14, and 28 and in adults (day 84). Across all ages, V(max) ATPase of fibers was significantly higher than ATP(iso). The reserve capacity for ATP consumption [1 - (ratio of ATP(iso) to V(max) ATP(ase))] was remarkably constant ( approximately 55-60%) across age groups, although at day 28 and in adults the reserve capacity for ATP consumption was slightly higher for fibers expressing MHC(Slow) compared with fast MHC isoforms. At day 28 and in adults, both V(max) ATPase and ATP(iso) were lower in fibers expressing MHC(Slow) followed in rank order by fibers expressing MHC(2A), MHC(2X), and MHC(2B). For fibers expressing MHC(Neo), V(max) ATPase, and ATP(iso) were comparable to values for adult fibers expressing MHC(Slow) but significantly lower than values for fibers expressing fast MHC isoforms. We conclude that postnatal transitions from MHC(Neo) to adult fast MHC isoform expression in Dia(m) fibers are associated with corresponding but disproportionate changes in V(max) ATPase and ATP(iso).
authors.affiliation: Departments of Anesthesiology and Physiology and Biophysics, Mayo Medical School, Rochester, Minnesota 55905, USA. sieck.gary@mayo.edu
authors.forename: Gary C
authors.initials: GC
authors.lastname: Sieck
authors.forename: Y S
authors.initials: YS
authors.lastname: Prakash
authors.forename: Young-Soo
authors.initials: YS
authors.lastname: Han
authors.forename: Yun-Hua
authors.initials: YH
authors.lastname: Fang
authors.forename: Paige C
authors.initials: PC
authors.lastname: Geiger
authors.forename: Wen-Zhi
authors.initials: WZ
authors.lastname: Zhan
mesh_terms: D000205:Actomyosin / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000375:Aging / Q000378:metabolism; D000465:Algorithms; D000818:Animals; D001835:Body Weight / Q000502:physiology; D003964:Diaphragm / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism*; D007536:Isomerism; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000201:enzymology / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000096:biosynthesis / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D019289:Pyruvic Acid / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D009243:NAD; D019289:Pyruvic Acid; D000255:Adenosine Triphosphate; D000205:Actomyosin; D007770:L-Lactate Dehydrogenase; D000251:Adenosine Triphosphatases; D018995:Myosin Heavy Chains