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|Title:||High activity antioxidant enzymes protect flying-fox haemoglobin against damage: an evolutionary adaptation for flight?||Contributor(s):||Reinke, N (author); O'Brien, GM (author)||Publication Date:||2006||DOI:||10.1007/s00360-006-0094-7||Handle Link:||https://hdl.handle.net/1959.11/586||Abstract:||Flying-foxes are better able to defend haemoglobin against autoxidation than non-volant mammals such as sheep. When challenged with the common physiological oxidant, hydrogen peroxide, haemolysates of flying-fox red blood cells (RBC) were far less susceptible to methaemoglobin formation than sheep. Challenge with 1-acetyl-2-phenylhydrazine (APH) caused only half as much methaemoglobin formation in flying-fox as in ovine haemolysates. When intact cells were challenged with phenazine methosulfate (PMS), flying-fox RBC partially reversed the oxidant damage, and reduced methaemoglobin from 40 to 20% over 2 h incubation, while ovine methaemoglobin remained at 40%. This reflected flying-fox cells' capacity to replenish GSH fast enough that it did not deplete beyond 50%, while ovine RBC GSH was depleted to around 20%. The greater capacity of flying-foxes to defend haemoglobin against oxidant damage may be explained in part by antioxidant enzymes catalase, superoxide dismutase and cytochrome-b 5 reductase having two- to four-fold higher activity than in sheep (P < 0.001). Further, their capacity to limit GSH depletion to 50% and reduce methaemoglobin (in the presence of glucose), despite ongoing exposure to PMS may result from having ten-fold higher activity of G6PD and 6PGD than sheep (P < 0.001), indicating the presence of a very efficient pentose phosphate pathway in flying-foxes.||Publication Type:||Journal Article||Source of Publication:||Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology, 176(8), p. 729-737||Publisher:||Springer||Place of Publication:||Heidelberg, Germany||ISSN:||0174-1578||Field of Research (FOR):||060104 Cell Metabolism||Peer Reviewed:||Yes||HERDC Category Description:||C1 Refereed Article in a Scholarly Journal||Statistics to Oct 2018:||Visitors: 132
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