Fenton-type reactions and iron concentrations in the midgut fluids of tree-feeding caterpillars
Barbehenn, Raymond V.; Dodick, Todd; Poopat, Umpai; Spencer, Brooke
2005-09
Citation
Barbehenn, Raymond; Dodick, Todd; Poopat, Umpai; Spencer, Brooke (2005)."Fenton-type reactions and iron concentrations in the midgut fluids of tree-feeding caterpillars." Archives of Insect Biochemistry and Physiology 60(1): 32-43. <http://hdl.handle.net/2027.42/48689>
Abstract
Peroxides are formed in the midgut fluids of caterpillars when ingested tannins and other phenolic compounds oxidize. If these peroxides broke down in the presence of redox-active metal ions, they would form damaging free radicals (Fenton-type reactions). Elemental iron is present in relatively large amounts in leaves and artificial diets, but little is known about its concentration and redox state in midgut fluids, or the extent of Fenton-type reactions in these conditions. This study compared the levels of hydroxyl radicals and iron in the midgut fluids of two species of caterpillars: Orgyia leucostigma , in which phenol oxidation is limited, and Malacosoma disstria , in which phenol oxidation is more extensive. We tested two hypotheses: (1) higher levels of hydroxyl radicals are formed in M. disstria (consistent with the higher concentrations of hydrogen peroxide in this species), and (2) lower concentrations of iron are present in O. leucostigma (providing greater protection of its midgut fluids from oxidative damage). Hydroxyl radical levels increased greatly in M. disstria , but not in O. leucostigma , when they consumed a tannin-containing diet, supporting the first hypothesis. Protein oxidation was also significantly increased in the midgut fluids of M. disstria that ingested tannic acid, consistent with hydroxyl radical damage. Contrary to the second hypothesis, similar concentrations of iron (70 μM) remained in solution or suspension in both species of caterpillars on an artificial diet. Over 90% of this iron appeared to be in the reduced (catalytically active) state in both species. We conclude that tree-feeding caterpillars protect their midgut fluids from oxidative damage caused by Fenton-type reactions by limiting the formation of peroxides, rather than by limiting the availability of reduced iron. Arch. Insect Biochem. Physiol. 60:32–43, 2005. © 2005 Wiley-Liss, Inc.Publisher
Wiley Subscription Services, Inc., A Wiley Company
ISSN
0739-4462 1520-6327
Other DOIs
PMID
16116620
Types
Article
URI
http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=retrieve&db=pubmed&list_uids=16116620&dopt=citationMetadata
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