A delayed rectifier potassium current in Xenopus oocytes.

Abstract:

:A delayed voltage-dependent K+ current endogenous to Xenopus oocytes has been investigated by the voltage-clamp technique. Both activation and inactivation of the K+ current are voltage-dependent processes. The K+ currents were activated when membrane potential was depolarized from a holding potential of -90 to -50 mV. The peak current was reached within 150 ms at membrane potential of +30 mV. Voltage-dependent inactivation of the current was observed by depolarizing the membrane potential from -50 to 0 mV at 10-mV increments. Voltage-dependent inactivation was a slow process with a time constant of 16.5 s at -10 mV. Removal of Ca2+ from the bath has no effect on current amplitudes, which indicates that the current is Ca2+)-insensitive. Tail current analysis showed that reversal potentials were shifted by changing external K+ concentration, as would be expected for a K(+)-selective channel. The current was sensitive to quinine, a K+ channel blocker, with a Ki of 35 microM. The blockade of quinine is voltage-independent in the range of -20 to +60 mV. Whereas oocytes from the same animal have a relatively homogeneous current distribution, average amplitude of the K+ current varied among oocytes from different animals from 30 to 400 nA at membrane potential of +30 mV. Our results indicate the presence of the endogenous K+ current in Xenopus oocytes with characteristics of the delayed rectifier found in some nerve and muscle cells.

journal_name

Biophys J

journal_title

Biophysical journal

authors

Lu L,Montrose-Rafizadeh C,Hwang TC,Guggino WB

doi

10.1016/S0006-3495(90)82632-1

subject

Has Abstract

pub_date

1990-06-01 00:00:00

pages

1117-23

issue

6

eissn

0006-3495

issn

1542-0086

pii

S0006-3495(90)82632-1

journal_volume

57

pub_type

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