title: Contractile properties of rat single muscle fibers and myosin and troponin isoform expression after hypergravity.
abstract: The effects of 19 days of hypergravity (HG) were investigated on the biochemical and physiological properties of the slow soleus muscle and its fast agonist, the plantaris. HG was induced by rotational centrifugation that led to a 2-G gravity level. The HG rats were characterized by a slower body growth than control, whereas the soleus muscle mass was increased by 15%. Using electrophoretic techniques, we showed that the distribution of myosin heavy chain and troponin T isoforms was not modified after HG in both soleus and plantaris. In contrast, the isoform expression pattern of two troponin subunits, troponin I and troponin C, was changed in a slow-to-fast manner only in the soleus. From tension-pCa relationships, changes in Ca(2+) activation threshold by 0.18 pCa unit indicated a decrease in Ca(2+) sensitivity and an increase in the slope of the curve, attesting to a higher cooperativity along the thin filament after HG. Comparison of our HG data with previous results in microgravity conditions indicated that muscle characteristics, except muscle mass, did not evolve linearly from 0 to 2 G.
authors.affiliation: Laboratory of Neuromuscular Plasticity, Institut Fédératif de Recherche en Protéomique 118, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq cedex, France. Laurence.Stevens@univ-lille1.fr
authors.forename: Laurence
authors.initials: L
authors.lastname: Stevens
authors.forename: Cyril
authors.initials: C
authors.lastname: Bozzo
authors.forename: Tatiana
authors.initials: T
authors.lastname: Nemirovskaya
authors.forename: Valerie
authors.initials: V
authors.lastname: Montel
authors.forename: Maurice
authors.initials: M
authors.lastname: Falempin
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Mounier
mesh_terms: D000818:Animals; D018471:Hypergravity; D008297:Male; D009119:Muscle Contraction; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D014018:Tissue Distribution; D014336:Troponin / Q000378:metabolism*
chemical_list: D020033:Protein Isoforms; D014336:Troponin; D018995:Myosin Heavy Chains