The effect of cyanide and carbon monoxide on the electrical potential and resistance of cell membranes.

The rapid reduction in cell electropotentials induced by metabolic inhibitors is strong evidence for an electrogenic ion pump. According to Ohm's law, such a depolarization might be explained by a reduction in electric current, I, with unidirectional transport of a given ion, or an increase in permeability (decrease in resistance). With cells of etiolated seedlings of Pisum sativum L. cv. Alaska and Zea mays cv. Golden Bantam, carbon monoxide inhibition, which occurs only in the dark and is readily reversed by light, allows repeated cycling of depolarization and repolarization; there is no effect on cell membrane resistance. In contrast, cyanide inhibition results in a marked increase in membrane electrical resistance; with cyanide following repeated pulses of current used in measuring cell membrane resistance, the resistance eventually (about 10 minutes) shows an abrupt drop as in the "punch-through" effect reported by H. G. L. Coster (1965. Biophys. J. 5: 669-686).