Effects of ethanol on amino acid uptake by rat liver cells

The effects of ethanol on amino acid uptake were investigated in primary cultures of parenchymal cells isolated from adult rat liver. Sodium-dependent and energy-requiring amino acid transport was studied by measuring the uptake of the nonmetabolizable acid, alpha-amino isobutyric acid (AIB). Ethanol (80 to 100 mM) inhibits both basal and insulin-stimulated AIB uptake, measured after 21 hours of exposure to ethanol. Both the initial rate and cumulative uptake of AIB are inhibited. Although inhibition of basal uptake may involve an effect on more than one system for amino acid transport, the inhibition of insulin-stimulated AIB uptake suggests a major effect on the "A" system. The inhibition is dependent on the concentration of ethanol and results in an increase in Km, but no change in Vmax. Blocking the metabolism of ethanol by pyrazole does not prevent the inhibition of AIB uptake. Under these conditions, the presence of ethanol, rather than its metabolism, appears to inhibit amino acid transport. Inhibition of amino acid transport by ethanol may play a role in the ethanol-induced interference with hepatic gluconeogenesis and protein synthesis.