Permeability changes induced by electric impulses in vesicular membranes

Electric impulses were found to cause transient permeability changes in the membranes of vesicles storing biogenic amines. Release of catecholamines induced by electric fields (of the order of 20 kV/cm and decaying exponentially with a decay time of about 150 μsec) was studied, using the chromaffin granules of bovine adrenomedullary cells as a vesicular model system. Far-UV-absorption spectroscopy was applied to determine the amount of catecholamines released from suspended vesicles. A polarization mechanism is suggested for the induction of short-lived permeability changes caused by electric fields. Such transient changes in permeability may possibly represent a part of the sequence of events leading to stimulated neurohumoral secretion.