Charge movement in cut twitch fibres of Rana temporaria containing 0.1 mM EGTA.
1. Charge movement was studied in the cut twitch fibres of Rana temporaria with a double Vaseline-gap voltage-clamp technique. 2. In fibres containing 0.1 mM EGTA, the I gamma hump component of charge movement was either unresolvable or had a brief duration at all potentials. In the steady-state charge-voltage (Q-V) plots that were separable into the less voltage dependent (Q beta) and more voltage dependent (Q gamma) components, the amount of Q gamma was 0.9 +/- 0.1 nC microF-1. (mean +/- S.E.M., n = 18). 3. Fibres containing 20 mM EGTA showed broad I gamma humps at about -45 mV. The addition of 1.8 mM total Ca2+ to the end-pools accelerated the rising phase and abbreviated the duration of the hump. 4. I gamma in fibres containing 0.1 mM EGTA resembled those in intact fibres when recorded at similar low temperatures. 5. These results explain the controversy concerning the variable appearance of I gamma humps in cut fibres.
Hui
C S
CS
Department of Physiology and Biophysics, Indiana University Medical Center, Indianapolis 46202, USA. cshui@hyrax.iupui.edu
Chen
W
W
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology*; D003080:Cold Temperature; D004533:Egtazic Acid / Q000494:pharmacology*; D004553:Electric Conductivity; D007700:Kinetics; D008564:Membrane Potentials / Q000502:physiology; D009119:Muscle Contraction / Q000187:drug effects*; D018485:Muscle Fibers, Skeletal / Q000737:chemistry / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011896:Rana temporaria
D002614:Chelating Agents; D004533:Egtazic Acid; D002118:Calcium