The Mechanism of Suppression of GAP Junctional Intercellular Communication by 50-Hz Magnetic Fields

Abstract

In our previous studies, we found that a 50-Hz magnetic field exposure inhibited gap junctional intercellular communication (GJIC). A pulsed magnetic field (PMF) is more effective than a 50-Hz sinusoidal magnetic field in downregulation of the GJIC. Protein kinase C (PKC) is known to phosphorylate connexins and to downregulation gap junctions. Several investigators have noted that extremely low-frequency magnetic field exposure activates PKC. We hypothesized that PKC may be involved in the suppression of GJIC by a PMF. An experiment with the PKC inhibitor stawosporine (STS) or palmitoyl carnitine (PMC) was carried out. Chinese hamster lung (CHL) cells were exposed to 50 Hz at an average flux density of 0.8 mT for 24 h. They were treated with PKC inhibitor (STS or PMC) at different concentrations during the last hour. The results showed that the suppression of GJIC induced by PMF was dramatically inhibited in the presence of 10 nM STS or 10 μM PMC. We conclude that the inhibition of GJIC induced by a PMF may be due mainly to hyperphosphorylation of gap junctional connexins.