Hydrogen peroxide detoxification in the midgut of the blood-sucking insect, Rhodnius prolixus

Here we investigated H2O2 production and detoxification in the hematophagou s hemiptera, Rhodnius prolixus. Superoxide dismutase (SOD) catalyzes the di smutation of superoxide radical (O-2(-)). This reaction produces hydrogen p eroxide, which is scavenged by antioxidant enzymes such as catalase (CAT). SOD and CAT activities were found in all tissues studied, being highest in the midgut. CAT was dose-dependently inhibited in vivo by injections of 3-a mino-1,2,4-triazole (AT). Insects treated with AT showed a twofold increase in H2O2 levels. Injection of DL-buthionine-[S, R]-sulfoximine (BSO), an in hibitor of glutathione synthesis, also resulted in a fourfold increase in H 2O2, together with stimulation of CAT activity. Simultaneous administration of both AT and BSO had a synergistic effect on midgut H2O2 content. Taken all together, our results suggest that CAT and glutathione-dependent mechan isms cooperate to control H2O2 concentration in the midgut cell and prevent hydroxyl radical generation by Fenton reaction in this tissue. (C) 2001 Wi ley-Liss, Inc.