DELTA-AMINOLEVULINIC-ACID DEHYDRATASE ENZYME-ACTIVITY IN BLOOD, BRAIN, AND LIVER OF LEAD-DOSED DUCKS

Mallard ducks [Anas platyrhynchos] were dosed with a single shotgun pellet (approximately 200 mg Pb). After 1 mo. there was about 1 ppm Pb in the blood, 2.5 in the liver and 0.5 in the brain. Pb-induced inhibition of .delta.-aminolevulinic acid dehydratase enzyme in blood and cerebellum was much greater than in cerebral hemisphere or liver and was strongly correlated with the Pb concentration in these tissues. The cerebellar portion of the brain was more sensitive to .delta.-aminolevulinic acid dehydratase enzyme inhibition by Pb than were the other tissues examined. There was also a greater increase in the glial cell marker enzyme, butyrylcholinesterase, in cerebellum than in cerebral hemisphere, suggesting that nonregenerating neuronal cells were destroyed by Pb and replaced by glial cells in that portion of the brain. Even partial loss of cerebellar tissue is severely debilitating in waterfowl, because functions critical to survival such as visual, auditory, motor and reflex responses are integrated at this brain center.