Activation of two types of fibres in ferret,Mustela putorius furo,cremaster muscle |
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Authors: | J Noireaud J P Louboutin E Thaon A Elkhammari C Huchet C Léoty |
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Institution: | (1) Laboratory of General Physiology, URA 1340, National Veterinary School, CP 3013, F-44087 Nantes Cedex 03, France |
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Abstract: | Summary 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(<400 m2) 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) and 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 Ca2+-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.Abbreviations a
i
Na
intracellular sodium activity
- ATPase
myosin adenosine triphosphatase
- D600
gallopamil
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E
m
membrane potential
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E
r
resting potential
- EDL
muscle, extensor digitorum longus muscle
- HEPES
N-2-hydroxyethylpiperazine-N -2-ethanesulphonic acid
- e.c.
excitation-contraction
- SDHase
succinate dehydrogenase
- NADHase
nicotinamide adenine, dinucleotide hydrogen-diaphorase
- SOL
muscle, soleus muscle
-
T
time constant of relaxation
- TEACI
tetraethylammonium chloride
- Ca]o, K]o, Na]o
extracellular calcium, potassium, sodium concentration |
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Keywords: | Cremaster Ferret Skeletal muscle Calcium |
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