The effect of temperature on charge movement repriming in amphibian skeletal muscle fibers.
Cut twitch muscle fibers, mounted in a triple Vaseline-gap chamber, were used to study the effects of temperature on intramembranous charge movement and, in particular, on the repriming of charge 1 (the intramembranous charge that normally moves in the potential range between -100 and +40 mV). Changing the holding potential from -90 to 0 mV modified the voltage distribution of charge movement but not the maximum movable charge. Temperature changes between 16 and 5 degrees C did not modify the fiber linear capacitance, the maximum nonlinear intramembranous charge, or the voltage distribution of charge 1 and charge 2 (the intramembranous charge moving in the membrane potential range between approximately -4 and -160 mV). We used a pulse protocol designed to study the repriming time course of charge 1, with little contamination from charge 2. The time course of charge movement repriming at 15 degrees C is described by a double exponential with time constants of 4.2 and 25 s. Repriming kinetics were found to be highly temperature dependent, with two rate-limiting steps having Q10 (increase in rate of a process by raising temperature 10 degrees C) values of 1.7 and 7.1 above and below 11.5 degrees C, respectively. This is characteristic of processes with a high energy of activation and could be associated with a conformational change of the voltage sensor or with the interaction between the voltage sensor and the calcium release channel.
Gonzalez
A
A
Laboratorio de Biofisica del Musculo, Centro de Biofisica y Bioquimica, Instituto Venezolano de Investigaciones Cientificas, Caracas, Venezuela.
Caputo
C
C
D000818:Animals; D001001:Anura; D066298:In Vitro Techniques; D007700:Kinetics; D008564:Membrane Potentials; D009068:Movement; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D018408:Patch-Clamp Techniques; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors