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LIMITATIONS IN THE USE OF MAGNETIC FIELDS TO EXAMINE GAP JUNCTION COMMUNICATION
Citation:
Wang, X., D E. House, J. Page, AND C F. Blackman. LIMITATIONS IN THE USE OF MAGNETIC FIELDS TO EXAMINE GAP JUNCTION COMMUNICATION. Presented at Intl. Gap Junction Conference, Honolulu, Hawaii, 08/4-9/2001.
Description:
OBJECTIVE: We have previously shown that gap junction communication (GJC) in mouse primary hepatocytes can be enhanced by treatment with physiological levels of melatonin, and that 45-Hz magnetic fields can eliminate this enhancement in a time-dependent manner. The objective of this presentation is to examine the frequency-dependence of this reduction in GJC in primary hepatocytes due to coincident melatonin and magnetic field exposures. METHODS: Primary hepatocytes, prepared from B6C3F1 male mice according to the method of Klaunig et al., were treated with 0.4 nM melatonin for 24 hours. Treated cells were then exposed to sinusoidal magnetic fields, 38.4 uT DC and parallel 40, 42.5, 45, 47.5 or 50- Hz AC at 24.4 uTrms, for selected time periods up to 3 hours. Following treatment, the cells were microinjected with Lucifer yellow dye and the percentage of nearest neighbor cells to which the dye transferred (dye coupling) was determined. RESULTS: The amount of dye coupling was reduced from 96% (sham treatment) to 80% under the 45-Hz magnetic field exposure condition, and that reduction reached maximal value by 1.5 hours and persisted there at later exposure times. Exposure at either 42.5 or 47.5 Hz caused a lesser reduction in GJC over the 3-hr treatment, whereas exposure at 40 or 50 Hz caused very little or no
change in GJC over the same exposure period. DISCUSSION: In this presentation we show that GJC in melatonin-treated hepatocytes can be altered by exposure to a narrow frequency range of magnetic fields. The time-dependent changes observed in GJC, due to the magnetic field exposure, are of a time scale that is consistent with plasma-membrane phenomenon involving second messenger systems for modulation. The ability of a physiological concentration of melatonin and of magnetic fields to modulate GJC may
provide a basis to begin molecular level studies of gap junction regulation, which could yield insight into tumor promotion or suppression mechanisms.