Lead induced alterations in nitrite and nitrate levels in different regions of the rat brain

Nitric oxide (NO) is a free radical synthesized by nitric oxide synthase (N OS) during the conversion of L-arginine to citrulline. Lead (Pb) affects ne uronal functioning in the rat brain. Nitric oxide, a neuronal messenger has a short half life and converts immediately into nitrite and nitrate. The p resent study is designed to determine lead-induced alterations in NO produc tion by measuring nitrite and nitrate in the cerebellum, the hippocampus, t he frontal cortex and the brain stem of the rat brain. Male Sprague-Dawley rats were treated with lead acetate (5 and 15 mg/kg body wt.) by intraperit oneal injection. The control and experimental rats were sacrificed at the e nd of 7 and 14 days after treatment and different regions of the brain were isolated. Nitrite and nitrate (NOx) levels were estimated by the chemilumi nescent method using the NOA 280 (Sievers). The data suggested dose-depende nt and region-specific responses to lead. Both treatments of lead reduced N Ox levels in the cerebellum and the hippocampus. However, the frontal corte x and the brain stem responded differently to Pb exposure. NOx levels in th e frontal cortex were significantly increased in rats treated with low and high doses of Pb for 7 days but not in rats treated for 14 days, whereas in the brain stem, NOx levels were increased in a dose- and time-dependent ma nner. Although, the response was time-dependent, the variation between 7- a nd 14-day treatment was not clearly delineated. These results provide addit ional evidence that Pb exposure alters NO-production in rat brain leading t o neuronal dysfunction. (C) 2000 Elsevier Science Inc. All rights reserved.