ACETALDEHYDE METABOLISM BY BRAIN MITOCHONDRIA FROM UCHA AND UCHB RATS

The acetaldehyde (AcH) oxidizing capacity of total brain homogenates f rom the genetically high-ethanol consumer (UChB) appeared to be greate r than that of the low-ethanol consumer (UChA) rats. To gain further i nformation about this strain difference, the activity of aldehyde dehy drogenase (AlDH) in different subcellular fractions of whole brain hom ogenates from naive UChA and UChB rat strains of both sexes has been s tudied by measuring the rate of AcH disappearance and by following the reduction of NAD to NADH. The results demonstrated that the higher ca pacity of brain homogenates from UChB rats to oxidize AcH when compare d to UChA ones was because the UChB mitochondrial low K-m AlDH exhibit s a much greater affinity for NAD than that of the UChA rats, as evide nced by four- to fivefold differences in the K-m values for NAD. But t he dehydrogenases from both strains exhibited a similar maximum rate a t saturating NAD concentrations. Because intact brain mitochondria iso lated from UChB rats oxidized AcH at a higher rate than did mitochondr ia from UChA rats only in state 4, but not in state 3, this strain dif ference in AlDH activity might be restricted in vivo to NAD dispositio n.