Lipoxygenase and other enzymes of arachidonic acid metabolism in the brain of chicks affected by nutritional encephalomalacia

Abstract 1. 1. Prostaglandin endoperoxide synthetase (PES) and lipoxygenase (Lox) activities were compared in the cerebella and cerebra of vitamin E-sufficient young chicks and in chicks in which nutritional encephalomalacia (NE) was induced by a diet deficient in vitamin E. 2. 2. Eicosanoid production patterns were qualitatively similar in the brains of both groups of chicks, but prostaglandin production was 50–60% less in cerebella of ataxic chicks, compared to control cerebella, while the opposite trend was observed in the cerebellar Lox pathway, as measured by radioimmunoassay of 15-HETE. 3. 3. Cerebellar phospholipase A, activity was twice that of the cerebrum but was not affected by NE. 4. 4. Purification of Lox activity from the cerebellar homogenates produced a lower yield and enrichment when the starting material was taken from ataxic chicks, compared to the controls. 5. 5. In addition there were qualitative differences in the purified fractions from both groups, as seen by pH optima and kinetics. 6. 6. The results are consistent with the view that the cerebellum has less antioxidant protection than the cerebrum and that its higher phospholipase A 2 activity and greater propensity to oxygenate arachidonic acid via the Lox pathway at the expense of the PES pathway may render this region of the brain particularly vulnerable to oxidative damage in NE.