Changes in (Na++K+)ATPase Activity and the Composition of Surface Carbohydrates in Erythrocyte Membranes in Alcoholics

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Abstract
(Na++K+)ATPase activity and sensitivity to the inhibitory effect of ethanol and noradrenaline in vitro as well as the concentrations of sialic acid, galactose, and hexosamine were determined in erythrocyte membranes in 20 healthy controls and in 20 alcoholic patients within 24 hr of withdrawal. Basal (Na++K+)ATPase activity, the sensitivity of the enzyme to inhibition by ethanol and noradrenaline added in vitro, and the concentrations of sialic acid and galactose were significantly reduced in the patients (p < 0.0005). All of these abnormalities were significantly correlated to each other as well as to the estimated dairy quantity of ethanol consumed. After enzymatic removal of terminal sialic acid and terminal and sialic acid-bound β-galactose, the (Na++K+)ATPase differences between the patients and the controls were eliminated. The results showed that the previously reported reduced inhibition of (Na++K+)ATPase by ethanol in the presence of noradrenaline in brain membranes in chronically ethanol-fed animals is also found in erythrocyte membranes in alcoholic humans. Abnormal carbohydrate composition of glycoiipids and/or glycoproteins of the membrane surface appeared to be related to the (Na++K+)ATPase changes, possibly due to interference either with K+ transport or surface electrostatics or, directly or indirectly, with the conformation of (Na++K+)ATPase.