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Oxygen‐sensing pathway for SK channels in the ovine adrenal medulla
Author(s) -
Keating Damien J,
Rychkov Grigori Y,
Giacomin Paul,
Roberts Michael L
Publication year - 2005
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.2010.04279.x
Subject(s) - rotenone , biophysics , extracellular , patch clamp , oxygen , chemistry , intracellular , chromaffin cell , nadph oxidase , hypoxia (environmental) , microbiology and biotechnology , reactive oxygen species , endocrinology , biochemistry , adrenal medulla , biology , mitochondrion , catecholamine , receptor , organic chemistry
SUMMARY 1. The intracellular pathways that modulate the opening of oxygen‐sensitive ion channels during periods of hypoxia are poorly understood. Different tissues appear to use either NADPH oxidase or a rotenone‐sensitive mechanism as an oxygen sensor. The aim of the present study was to identify the oxygen‐sensing pathway in the oxygen‐sensitive sheep adrenal medullary chromaffin cell (AMCC). 2. The whole‐cell patch‐clamp technique was used to measure K + currents in dissociated adult ovine chromaffin cells as well as SK channel currents expressed in the H4IIE cell line. 3. Diphenyliodonium, an inhibitor of NADPH oxidase, had no effect on the hypoxia‐evoked closure of K + channels in primary AMCC, whereas the mitochondrial inhibitor rotenone abolished the hypoxia‐evoked response. Both these compounds significantly reduced K + current amplitude under normoxic conditions. 4. One possible mechanism through which the oxygen sensor may modulate K + channel activity is by altering the redox state of the cell. In sheep AMCC, altering the redox state by the addition of H 2 O 2 to the extracellular solution increased K + conductance. 5. The oxygen‐sensitive K + (K o 2 ) channels in sheep chromaffin cells are from the SK family and the whole‐cell conductance of cells expressing mouse SK2 or SK3, but not human SK1, was increased by H 2 O 2 and decreased by the reducing agent dithiothreitol. 6. These studies show that, in sheep AMCC, K o 2 channels are modulated via a rotenone‐sensitive mechanism and that alteration of the cellular redox state mimics the change produced by alterations in P o 2 . In a heterologous expression system, SK2 and SK3 channels, the channels that initiate hypoxia‐evoked changes in AMCC function, are modulated appropriately by changes in cellular redox state.