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Effects on Rb + (K + ) uptake of HeLa cells in a high K + medium of exposure to a switched 1.7 tesla magnetic field
Author(s) -
Ikehara Toshitaka,
Park Ki Ho,
Yamaguchi Hisao,
Hosokawa Keiko,
Yoshizaki Kazuo,
Miyamoto Hiroshi,
Aizawa Katsuo,
Kinouchi Yohsuke
Publication year - 2000
Publication title -
bioelectromagnetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.435
H-Index - 81
eISSN - 1521-186X
pISSN - 0197-8462
DOI - 10.1002/(sici)1521-186x(200004)21:3<228::aid-bem9>3.0.co;2-i
Subject(s) - ionomycin , hela , ionophore , chemistry , biophysics , bapta , iberiotoxin , intracellular , nuclear magnetic resonance , potassium channel , membrane , cell , biochemistry , biology , physics
Effects of a switched, time‐varying 1.7 T magnetic field on Rb + (K + ) uptake by HeLa S3 cells incubated in an isosmotic high K + medium were examined. The magnetic flux density was varied intermittently from 0.07–1.7 T at an interval of 3 s. K + uptake was activated by replacement of normal medium by high K + medium. A membrane‐permeable Ca 2+ chelating agent (BAPTA‐AM) and Ca 2+ ‐de pendent K + channel inhibitors (quinine, charibdotoxin, and iberiotoxin) were found to reduce the Rb + (K + ) uptake by about 30–40%. Uptake of K + that is sensitive to these drugs is possibly mediated by Ca 2+ ‐dependent K + channels. The intermittent magnetic field partly suppress ed the drug‐sensitive K + uptake by about 30–40% (P < 0.05). To test the mechanism of inhibition by the magnetic fields, intracellular Ca 2+ concentration ([Ca 2+ ]c) was measured using Fura 2‐AM. When cells were placed in the high K + ; medium, [Ca 2+ ]c increased to about 1.4 times the original level, but exposure to the magnetic fields completely suppressed the increase (P < 0.01). Addition of a Ca 2+ ionophore (ionomycin) to the high K + medium increased [Ca 2+ ]c to the level of control cells, regardless of exposure to the magnetic field. But the inhibition of K + uptake by the magnetic fields was not restored by addition of ionomycin. Based on our previous results on magnetic field‐induced changes in properties of the cell membrane, these results indicate that exposure to the magnetic fields partly suppresses K + influx, which may be mediated by Ca 2+ ‐dependent K + channels. The suppress ion of K + fluxes could relate to a change in electric properties of cell surface and an inhibition of Ca 2+ influx mediated by Ca 2+ channels of either the cell plasma membrane or the inner vesicular membrane of intracellular Ca 2+ stores. Bioelectromagnetics 21:228–237, 2000. © 2000 Wiley‐Liss, Inc.