title: Activation of two types of fibres in ferret, Mustela putorius furo, cremaster muscle.
abstract: Some contractile, histochemical, morphological and electrophysiological properties of ferret, Mustela putorius furo, cremaster muscle have been estimated. Histochemical fibre typing revealed the presence of two types of fibres (type I 66.2%, type II 33.8%). Morphometry performed on ATPase-stained transverse sections showed that type I was composed of a large amount (40%) of small (less than 1400 microns2) cells. In mammalian Ringer two groups of fibres could be recognized on the basis of the values of resting potential (-69.7 mV and -59.1 mV) intracellular sodium activity (8.3 mmol.l-1 and 14.1 mmol.l-1, respectively). In experiments on fibre bundles, the elevation of extracellular potassium concentration to 15-200 mmol.l-1 produced contractures that consisted of a well-defined transient or phasic tension followed by a sustained or tonic tension. Properties of activation and inactivation of the tension analysed in small bundles of cut fibres (lengths 0.5-1.0 cm) were of fast- and slow-twitch type for phasic and tonic phase, respectively. In contrast to the phasic component of K contractures, the tonic phase was abolished by Ca2+ withdrawal and inhibited by Ni2+, Cd2+, Co2+, Gd3+ and gallopamil (D600). In Ca(2+)-free medium the sustained tension was restored by adding Sr2+. It is concluded that in ferret cremaster muscle the presence of slow-twitch fibres would give rise to the tonic component of the K contracture in which an extracellular source of activator Ca2+ is involved. The ability of these fibres to contract with a maintained tension for prolonged periods of time might participate in the temperature regulation of the testes.
authors.affiliation: Laboratory of General Physiology, URA 1340, National Veterinary School, Nantes, France.
authors.forename: J
authors.initials: J
authors.lastname: Noireaud
authors.forename: J P
authors.initials: JP
authors.lastname: Louboutin
authors.forename: E
authors.initials: E
authors.lastname: Thaon
authors.forename: A
authors.initials: A
authors.lastname: Elkhammari
authors.forename: C
authors.initials: C
authors.lastname: Huchet
authors.forename: C
authors.initials: C
authors.lastname: Léoty
mesh_terms: D000251:Adenosine Triphosphatases / Q000032:analysis; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002118:Calcium / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D005289:Ferrets / Q000502:physiology*; D005711:Gallopamil / Q000494:pharmacology; D006651:Histocytochemistry; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D009132:Muscles / Q000166:cytology / Q000201:enzymology / Q000502:physiology*; D009532:Nickel / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000493:pharmacokinetics
chemical_list: D005711:Gallopamil; D009532:Nickel; D012964:Sodium; D000251:Adenosine Triphosphatases; D011188:Potassium; D002118:Calcium