Acute inhibitory effect of alcohol on sodium-lithium countertransport

To assess a possible acute effect of environmental factors on sodium-lithium countertransport (SLC), we determined the activity of this transport system in 14 healthy volunteers, who are nonhabitual drinkers, before and 1 hour after intake of alcohol (0.8g/kg) with "Coke" as the vehicle. Alcohol significantly increased the "leak pathway" component of lithium efflux from a baseline value of 0.21 +/- 0.02 to 0.24 +/- 0.02 mmol/Lcell.h(p < 0.003); and reduced the Vmax of the transporter (0.38 +/- 0.05 to 0.31 +/- 0.04mmol/Lcell.h;p < 0.0005) without significantly changing its affinity for external sodium. The reduction in Vmax was dependent on the initial activity of the transporter (r2 = 0.5). A plot of reduction in Vmax against the product of initial Vmax value and blood alcohol level in each subject revealed a stronger relationship (r2 = 0.86), suggesting that the observed change in Vmax was also dependent on blood alcohol level. Coke alone did not change any of the parameters. We conclude that alcohol acutely inhibits SLC as well as alters erythrocyte membrane in a manner that increases passive lithium efflux.