Involvement of a pertussis toxin-sensitive G-protein in excitation-contraction coupling of intact and cut-end voltage-clamped skeletal muscle fibres
✍ Scribed by Aklesso Mouzou; Jean -Pierre Poindessault; Guy Raymond
- Publisher
- Springer
- Year
- 1992
- Tongue
- English
- Weight
- 277 KB
- Volume
- 421
- Category
- Article
- ISSN
- 0031-6768
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✦ Synopsis
In voltage-clamped frog muscle fibres 10 ng/ml PTX induced a decrease (~ 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 GTPyS (500 /d4) induced a simultaneous increase in tension (57 • 5 %) and charge amount displaced (40 • 7 %). By contrast, GDPBS decreased tension and charge movement by 35 • 5 % and 36 • 6 % respectively.