AJP - Cell Physiology, Vol 270, Issue 3 C892-C897, Copyright © 1996 by American Physiological Society
The effect of temperature on charge movement repriming in amphibian skeletal muscle fibers
A. Gonzalez and C. Caputo
Laboratorio de Biofisica del Musculo, Centro de Biofisica y Bioquimica, Instituto Venezolano de Investigaciones Cientificas, Caracas, Venezuela.
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.
