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A 50 Hz magnetic field blocks melatonin-induced enhancement of junctional
transfer in normal C3H/10T1/2 cells
Alejandro Ubeda 1 3, M. Angeles Trillo 1, Dennis E. House 2 and Carl
F. Blackman 2 3To whom correspondence should be addressed There is strong evidence that pineal melatonin is involved in controlling
neoplastic processes. We have reported that physiological, but not pharmacological
or sub physiological, concentrations of melatonin enhance intercellular
communication in normal C3H/10T1/2 fibroblasts. Gap junctional intercellular
communication intervenes in the control of cell proliferation and differentiation,
and seems to play a crucial role in suppression of tumor promotion. A
number of in vivo studies have shown that extremely low frequency (ELF)
magnetic fields (MF) can act as cancer promoters or co-promoters. In
vitro, 60 Hz MF have been reported to block melatonin-induced inhibition
of cell proliferation in human breast cancer cells. The mechanisms responsible
for the observed interactions of MF at the cellular level remain unknown.
In the present study melatonin was added to confluent fibroblasts at
a concentration of 10–10 M. Twenty-seven hours later, a fluorescent
dye was scrapeloaded into groups of cells and the transfer of the dye
to adjacent cells through gap junctions was quantified. Under these conditions
melatonin induced a significant increase of dye transfer; this increase
was not observed when the cultures were exposed to the MF for 30 min
before the scrape-load assay was performed. This finding reinforces previously
reported results suggesting that the in vivo oncostatic action of melatonin
could be exerted, in part, through modulation of the levels of gap junctional
intercellular communication. Also, the data indicate that ELF-MF could
counteract the melatonin-induced enhancement of junctional transfer. More Information about Magnetic Fields
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