HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ashcroft, F M Articles by Vergara, J Search for Related Content PubMed PubMed Citation Articles by Ashcroft, F M Articles by Vergara, J

The non-penetrating potentiometric dyes NK2367 and WW375 were used to investigate the effect of inward rectification on the weighted-average tubular membrane potential in single frog muscle fibres voltage clamped using a three-Vaseline-gap method. In 100 mM-K solution, when inward rectification was activated by hyperpolarization the steady-state amplitude of the transverse tubular system (T-system) optical signal was reduced, and its rise time was faster than that recorded for an equivalent depolarization. The voltage dependence of the optical attenuation followed that of inward rectification, increasing with increasing hyperpolarization. For a voltage-clamp step of -140 mV the optical attenuation was 0.72 which corresponds to a weighted-average T-system potential change of 100 mV. When inward rectification was blocked in a Cs, TEA solution the optical attenuation was also abolished. The voltage dependence of the block of the inward currents in solutions containing low concentrations of Cs was also reflected in the T-system optical signals. Our results were satisfactorily predicted by a radial cable model of the T-system, assuming the same specific inward rectifier conductance in surface and tubular membranes. This analysis predicts that the measured optical attenuation corresponds to a decrease in the tubular space constant, lambda T, from 120 micron under passive conditions to about 40 micron when inward rectification is fully, activated. The voltage dependence of inward rectification measured at the surface membrane was reasonably well predicted by assuming that the specific conductance obeyed a Boltzmann type of voltage dependence; the major effect of tubular decrements was to reduce the steepness of the total (surface + T-system) conductance-voltage relation.

This article has been cited by other articles:

				M. DiFranco, J. Capote, M. Quinonez, and J. L. Vergara Voltage-dependent Dynamic FRET Signals from the Transverse Tubules in Mammalian Skeletal Muscle Fibers J. Gen. Physiol., November 26, 2007; 130(6): 581 - 600. [Abstract] [Full Text] [PDF]

				C. E Woods, D. Novo, M. DiFranco, J. Capote, and J. L Vergara Propagation in the transverse tubular system and voltage dependence of calcium release in normal and mdx mouse muscle fibres J. Physiol., November 1, 2005; 568(3): 867 - 880. [Abstract] [Full Text] [PDF]

				O. M. Sejersted and G. Sjogaard Dynamics and Consequences of Potassium Shifts in Skeletal Muscle and Heart During Exercise Physiol Rev, October 1, 2000; 80(4): 1411 - 1481. [Abstract] [Full Text] [PDF]

				F. Cifuentes, J. Vergara, and C. Hidalgo Sodium/calcium exchange in amphibian skeletal muscle fibers and isolated transverse tubules Am J Physiol Cell Physiol, July 1, 2000; 279(1): C89 - C97. [Abstract] [Full Text] [PDF]