Format

Send to

Choose Destination
Biophys J. 1995 Sep;69(3):860-72.

Unilateral exposure of Shaker B potassium channels to hyperosmolar solutions.

Author information

1
Békésy Laboratory of Neurobiology, University of Hawaii, Honolulu 96822-2359, USA.

Abstract

This study tests the hypothesis that ion channels will be affected differently by external (extracellular) versus internal (cytoplasmic) exposure to hyperosmolar media. We looked first for effects on inactivation kinetics in wild-type Shaker B potassium channels. Although external hyperosmolar exposure did not alter the inactivation rate, internal exposure slowed both onset and recovery from fast inactivation. Differential effects on activation kinetics were then characterized by using a noninactivating Shaker B mutant. External hyperosmolar exposure slowed the late rising phase of macroscopic current without affecting the initial delay or early rising phase kinetics. By contrast, internal exposure slowed the initial steps in channel activation with only minimal changes in the later part of the rising phase. Neither external nor internal hyperosmolar exposure affected tail current rates in these noninactivating channels. Additionally, suppression of peak macroscopic current was approximately twofold smaller during external, as compared with internal, hyperosmolar exposure. Single-channel currents, observed under identical experimental conditions, showed a differential suppression equivalent to that seen in macroscopic currents. Apparently, during unilateral hyperosmolar exposure, changes in macroscopic peak current arise primarily from changes in single-channel conductance rather than from changes in equilibrium channel gating. We conclude that unilateral hyperosmolar exposure can provide information concerning the potential structural localization of functional components within ion-channel molecules.

PMID:
8519986
PMCID:
PMC1236315
DOI:
10.1016/S0006-3495(95)79960-X
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Elsevier Science Icon for PubMed Central
Loading ...
Support Center