Dual effects of charged amphiphiles on depolarization-contraction coupling in denervated rat soleus muscle.
Ionic currents and contraction were recorded under voltage clamp conditions in single fibres isolated from rat soleus muscles denervated for more than 20 days. The effects of amphiphiles on depolarization-contraction (d.c.) coupling in Na-free TEA-containing solutions were analyzed. An anionic amphiphile, sodium dodecyl sulfate (1-10 microM), caused a dose-dependent reduction of the contractile response at all amplitudes of depolarization while a cationic amphiphile, dodecyltrimethylamine (1-10 microM), increased the maximum developed tension with a shift in the contractile threshold. A neutral amphiphile, lauryl acetate (20 microM), induced no significant variation. The effects of charged amphiphiles were found to be strongly dependent on the external calcium concentration and on membrane potential. The effect of sodium dodecyl sulfate to decrease tension was reduced or changed to positive inotropy following hyperpolarization of the membrane by, respectively, +10 and +20 mV. In hyperpolarized (+20 mV) cells, dodecyltrimethylamine reduced the amplitude of the contraction. The results demonstrated that changes in Ca-binding properties of surface membrane modified d.c. coupling in denervated slow twitch skeletal muscle.
Léoty
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C
Laboratory of General Physiology, URA CNRS 1340, National Veterinary School, University of Nantes, France.
Noireaud
J
J
D000818:Animals; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009121:Muscle Denervation; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D009467:Neuromuscular Depolarizing Agents / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012508:Sarcolemma / Q000378:metabolism; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology
D009467:Neuromuscular Depolarizing Agents; D012967:Sodium Dodecyl Sulfate; D002118:Calcium