Involvement of a pertussis toxin-sensitive G-protein in excitation-contraction coupling of intact and cut-end voltage-clamped skeletal muscle fibres.
In voltage-clamped frog muscle fibres 10 ng/ml PTX induced a decrease (approximately 35%) of tension when applied externally. Internal application in cut-end fibres significantly depressed tension after 20 min. This effect increased with time to reach 65% after 60 min. PTX shifted the voltage-dependent inactivation curve of tension by 30 mV towards hyperpolarizations and this was counteracted by raising external calcium concentration. The toxin induced a parallel decrease in tension and voltage-sensitive charge movement (49 +/- 9% and 52 +/- 6% respectively; n = 6). This was not counteracted by prior impregnation with forskolin. Internally applied GTP gamma S (500 microM) induced a simultaneous increase in tension (57 +/- 5%) and charge amount displaced (40 +/- 7%). By contrast, GDP beta S decreased tension and charge movement by 35 +/- 5% and 36 +/- 6% respectively.
Mouzou
A
A
Laboratory of General Physiology, URA C.N.R.S. 290, Faculty of Sciences, Poitiers, France.
Poindessault
J P
JP
Raymond
G
G
D000818:Animals; D005576:Colforsin / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009132:Muscles / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects; D037342:Pertussis Toxin; D011895:Rana ridibunda; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D010566:Virulence Factors, Bordetella; D005576:Colforsin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D037342:Pertussis Toxin; D019204:GTP-Binding Proteins