D2O-induced cell excitation.

The effects of deuterium oxide (D2O) on giant internodal cells of the fresh water alga Chara gymnophylla, were investigated. D2O causes membrane excitation followed by potassium leakage. The primary effect consists of an almost instantaneous membrane depolarization resembling an action potential with incomplete repolarization. A hypothesis was proposed which deals with an "osmotic stress" effect of D2O on membrane ion channels followed by the suppression of the electrogenic pump activity. The initial changes (potential spike and rapid K+ efflux) may represent the previously undetected link between the D2O-induced temporary arrest of protoplasmic streaming and the early events triggered at the plasma membrane level as the primary site of D2O action.