Feb 1, 1985

Inward rectification in the transverse tubular system of frog skeletal muscle studied with potentiometric dyes

The Journal of Physiology
F M AshcroftJ Vergara


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 pre...Continue Reading

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Mentioned in this Paper

Transverse Tubule of Muscle Cell
Resting Potentials
WW 375
Tetraethylammonium Hydroxide
Tubular Cells

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