Ethanol inhibition of active 86Rb(+)-transport: evidence for enhancement by sodium or calcium influx.

We investigated interactions between ethanol and active cation transport mediated by Na,K-ATPase in rat brain synaptoneurosomes. Conditions that increased internal sodium also increased sensitivity of transport to ethanol, whereas low-sodium medium had the opposite effect. Ethanol also blocked the stimulation of ouabain-sensitive transport, glucose uptake and hyperpolarization associated with sodium influx. Low calcium decreased, while the calcium ionophore A23187 increased, sensitivity to ethanol. Inhibition of mitochondrial respiration or incubation under anaerobic conditions increased sensitivity of transport to inhibition by ethanol, but did not prevent the effect of A23187. Consistent with increased sensitivity to ethanol by cell calcium, ethanol potentiated the inhibition of transport by A23187. Although transport under basal conditions does not appear very sensitive to ethanol, these data suggest that sensitivity to ethanol may be increased under conditions associated with increased neural activity, and that ethanol may reduce the transport response to electrical activity.