URATE PROTECTS A BLOODSUCKING INSECT AGAINST HEMIN-INDUCED OXIDATIVE STRESS

Urate at high concentrations (up to 5 mM) is found in the hemolymph of the blood-sucking bug, Rhodnius prolixus. Increased urate levels are observed in the days following a blood meal. Injecting hemin into the hemocoel increases both urate titer and TEARS formation in the hemolym ph. The urate response to hemin injection seems to arise from increase d synthesis by the fat body as urate secretion by this organ is stimul ated in vitro by incubation with hemin, and markedly counteracted by a llopurinol. Allopurinol injection also results in increased TEARS form ation in the hemolymph. High O-2 atmospheric conditions also increases hemolymph urate levels, confirming that urate release represents an a ntioxidant response. Urate concentrations at the range reported here m ight account for almost all free radical scavenging activity of the he molymph, as deduced from TRAP assay experiments, indicating that this is the major low molecular weight protection of this insect against ox idative insult. Since large amounts of hemin are produced in the midgu t following blood digestion, increased urate hemolymph levels are sugg ested to bean important protective biochemical adaptation to allow blo od feeding. Copyright (C) 1996 Elsevier Science Inc.