Protective effect of histidine on para-nonylphenol-enhanced hydroxyl free radical generation induced by 1-methyl-4-phenylpyridinium ion (MPP+) in rat striatum

The present study examined the antioxidant effect of histidine, a singlet oxygen (O-1(2)) scavenger, on para-nonylphenol (an environmental estrogen-like chemical)-enhanced hydroxyl radical ((OH)-O-.) generation induced by 1-methyl-4-phenylpyridinium ion (MPP+) in extracellular fluid of rat striatum. Rats were anesthetized, and sodium salicylate in Ringer's solution (0.5 nmol/mul/min) was infused through a microdialysis probe to detect the generation of (OH)-O-. as reflected by the non-enzymatic formation of 2,3-dihydroxybenzoic acid (DHBA) in the striatum. Introduction of para-nonylphenol (10 muM) significantly enhanced MPP+-induced (OH)-O-. generation. Histidine (25 mM) decreased the para-nonylphenol-enhanced (OH)-O-. fort-nation. Although the level of MPP+-induced (OH)-O-. formation trapped as DHBA after para-nonylphenol treatment increased, para-nonylphenol failed to increase either the level of dopamine and DHBA formation in the reserpinized animals, These results indicate that para-nonylphenol and MPP+-enhanced (OH)-O-. generation was based on O-1(2) production, and histidine may have a preventive effect on para-nonylphenol and MPP+-induced (OH)-O-. generation in rat striatum. (C) 2001 Elsevier Science B.V. All rights reserved.