Evidence suggests that some of the clinical effects of alcohol ingestion are not due to ethanol itself but to its metabolites NADH and ethanal (acetaldehyde). The NAD + /NADH concentration ratio in the cytosol is maintained at a value of 1000 (11). The administration of alcohol can lower this ratio by at least 10fold (12). The concentration of all substrates and products which thus use dehydrogenase enzymes will be affected by a change in the NAD + /NADH concentration ratio. Therefore a reduction of this concentration ratio will lower the concentration of the oxidised reactant and increase that of the reduced reactant. If either of these reactants has an important metabolic role, marked changes in their concentration could produce abnormal effects.
The increased ethanal levels which are seen after alcohol ingestion are further raised if the activity of aldehyde dehydrogenase is inhibited. Inhibitors of the enzyme include the higher aliphatic aldehydes which are known to be present in alcoholic beverages.
The following physiological effects can be, in part, explained by the changes in the NAD + /NADH ratio.
Was this article helpful?