title: HSP70 abundance and antioxidant capacity in feeding and fasting gray seal pups: suckling is associated with higher levels of key cellular defenses.
abstract: Heat shock proteins (HSPs) and antioxidants are key cellular defenses against stress. Seals routinely undergo protracted fasting, which is normally associated with physiological stress in other animals. We tested the hypotheses that (1) relative HSP70 protein abundance is higher in liver and blubber of fasting relative to suckling wild gray seal pups; (2) differences in HSP70 are mirrored in tissue superoxide dismutase (SOD) and catalase activity, as well as glutathione levels; (3) extracellular HSP70 correlates with hepatic and blubber HSP70 abundance; and (4) protein carbonylation, an index of oxidative damage, is lower in tissues with higher levels of these cellular stress markers. In contrast to our expectation, suckling pups had higher relative HSP70 abundance and glutathione levels in liver and blubber and higher hepatic catalase activity. Plasma HSP70 did not correlate with liver or blubber abundance of the protein. Suckling pups did not experience greater protein carbonylation, suggesting that cellular protective mechanisms prevent protein damage despite an apparent increase in cellular stress. SOD activity was not affected by nutritional state, but in blubber tissue, it was positively correlated with blubber thickness. Greater requirements for antioxidants and HSPs in suckling pups or in animals with thicker blubber could arise from rapid protein synthesis, high metabolic fuel availability, and/or exposure to lipophilic toxins. Developmental and nutritional changes in cellular defenses have important implications for gray seals' susceptibility to additional stress exposure.
authors.affiliation: Marine Biology and Ecology Research Centre, School of Marine Science and Engineering, Plymouth University, Drake Circus, Plymouth, Devon PL4 8AA, United Kingdom; 2Department of Biology, Mount Allison University, 63B York Street, Sackville, New Brunswick E4L 1E4, Canada; 3Department of Fisheries and Oceans, Maurice Lamontagne Institute, Mont Joli G5H 3Z4, Quebec, Canada.
authors.forename: Kimberley Ann
authors.initials: KA
authors.lastname: Bennett
authors.forename: Ian Sean
authors.initials: IS
authors.lastname: MacMillan
authors.forename: Mike
authors.initials: M
authors.lastname: Hammill
authors.forename: Suzanne
authors.initials: S
authors.lastname: Currie
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D005215:Fasting; D005978:Glutathione / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D009928:Organ Specificity; D050050:Protein Carbonylation; D046048:Seals, Earless / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D000975:Antioxidants; D018840:HSP70 Heat-Shock Proteins; D002374:Catalase; D013482:Superoxide Dismutase; D005978:Glutathione