Histological distribution of class III alcohol dehydrogenase in human brain

The distributions of class III alcohol dehydrogenase (ADH), a glutathione-d ependent formaldehyde dehydrogenase, and class I ADH in the human brain wer e examined immunohistochemically. The most intense immunostaining of class III ADH was observed in the dendrites and cytoplasm of cerebellar Purkinje cells. Scattered cerebral cortical neurons in layers IV and V, and some hip pocampal pyramidal neurons were also immunopositive. The neuronal distribut ion of class III ADH resembled that of the vulnerable neurons in patients w ith hypoxic encephalopathy, which in view of the intense staining in the Pu rkinje cells, raises the possibility that this enzyme contributes to the hy poxia and cerebellar degeneration suffered by chronic alcoholics, Perivascu lar and subependymal astrocytes, which contribute to the maintenance of the cerebral cellular milieu and isolate the brain from the systemic circulati on and cerebrospinal fluid, were also class III ADH positive. As the substr ates of this enzyme include intrinsic toxic formaldehyde, inflammatory inte rmediate of 20-hydroxy-leukoteiene B4, and possibly ethanol, the distributi on of class III ADH immunostaining indicates this enzyme contributes to the defence of the brain against degenerative processes. The finding that, unl ike ependymal cells, subependymal astrocytes were class III ADH positive, s uggests this enzyme may be useful for differentiating astrocytes and ependy mal cells. (C) 2000 Elsevier Science B.V. All rights reserved.