Voltage activated Na(+) channels were examined in GH3 cells, using the whole cell patch clamp method. Channel currents were recorded before, during, and after a 150 s exposure to a 125 mT static magnetic field. There was a slight shift in the current-voltage relationship and a less than 5% reduction in peak current during magnetic field exposure. More pronounced, however, was an increase in the activation time constant, tau(m), during and for at least 100 s following exposure to the field. This change in tau(m) was seen primarily at lower activation voltages. No change was noted in the inactivation time constant, tau(h). Changes were clearly temperature dependent, being evident only at and above 35 degrees C. These findings are consistent with the hypothesis that reorientation of diamagnetic anisotropic molecules in the cell membrane are capable of distorting imbedded ion channels sufficiently to alter their function. The temperature dependence of this phenomenon is probably due to the greater ease with which a liquid crystal membrane can be deformed.
Copyright 2003 Wiley-Liss, Inc.