Subcellular fractionation of alcohol and aldehyde dehydrogenase in the rat testicles

The subcellular distribution of the enzymes primarily involved in the metabolism of ethanol and acetaldehyde were made in the rat testis and in the epididymis. The enzymes measured were alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). They were NAD-dependent, temperature sensitive and displaying maximal activity in the presence of pyrophosphate buffer at pH 9.8. Both enzymes were readily measurable in the 10% (w/v) testicular and epididymal homogenates. The ADH activity was mainly localized in the nuclear and in the cytosolic fractions of the testis compared to the absence of measurable ADH activity in the epididymis. Testicular ALDH was measurable in all subcellular preparations, i.e. in the nuclear, in the mitochondrial, in the cytosolic and in the microsomal fractions. Maximal testicular ALDH activity was determined in both the nuclear and the cytosolic components compared to a lower microsomal ALDH activity. Determination of Km shows that cytosolic ALDH possesses the lowest apparent Km as contrasted with a high value for the mitochondrial ALDH. Testicular cytosolic ADH but not ALDH was noncompetitively inhibited by 3-methoxytyramine, histamine and d-amphetamine in vitro.