title: [Contractile properties of the isolated rat musculus soleus and single skinned soleus fibers at the early stage of gravitational unloading: facts and hypotheses].
abstract: The contractile properties of the postural rat soleus muscle at the early stage of the gravitational unloading (3-day rat hindlimb suspension) have been studied using different modes of muscle contraction (twitch and tetanic contraction of the isolated muscle, Ca-induced contraction of isolated skinned fibers). A significant enhancement of the twitch maximal tension of unloaded muscles without changes in time-dependent characteristics was observed, although the half-relaxation time tended to increase. The fiber diameter did not change (42.37 +/- 0.76 vs 43.43 +/- 1.15 microm in controls). The Ca-induced maximal isometric tension in unloaded soleus was significantly decreased (32.1 +/- 1.05 vs 37.6 +/- 1.52 mg in controls, p < 0.05). The maximal specific tension was respectively decreased (23.14 +/- 0.77 vs 27.6 +/- 2.36 kN/m in controls). The pCa50 in unloaded muscle decreased from 6.05 +/- 0.02 in controls to 5.97 +/- 0.02 (p < 0.05), indicating the loss of myofibrillar calcium sensitivity. The analysis with the calcium probe Fluo-4AM demonstrated that the intracellular [Ca2+] was sufficiently increased after hindlimb suspension. At the same time, the relative content of titin and nebulin did not change.
authors.forename: E V
authors.initials: EV
authors.lastname: Ponomareva
authors.forename: V V
authors.initials: VV
authors.lastname: Kravtsova
authors.forename: E V
authors.initials: EV
authors.lastname: Kachaeva
authors.forename: E G
authors.initials: EG
authors.lastname: Altaeva
authors.forename: I M
authors.initials: IM
authors.lastname: Vikhliantsev
authors.forename: Z A
authors.initials: ZA
authors.lastname: Podlubnaia
authors.forename: I I
authors.initials: II
authors.lastname: Krivoĭ
authors.forename: B S
authors.initials: BS
authors.lastname: Shenkman
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D009126:Muscle Relaxation; D018482:Muscle, Skeletal / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012518:Sarcomeres / Q000378:metabolism; D014893:Weightlessness
chemical_list: D003598:Cytoskeletal Proteins; D002118:Calcium