Characterization of heat- and osmotic-shock proteins in Atlantic salmon ({\it Salmo salar\/}) tissues

Todd Russell Smith, University of Rhode Island

Abstract

Protein induction in isolated tissues of Atlantic salmon (Salmo salar) subjected to hypersaline exposure was characterized in this research. But to provide a basis for studying protein induction by hypersaline conditions, protein induction was first characterized in response to heat shock and NaAsO$\sb2,$ known inducers of heat shock proteins (hsp). Therefore, isolated branchial tissue, erythrocytes and hepatic tissue were exposed to heat shock or sodium arsenite (NaAsO$\sb2).$ In subsequent experiments the tissues were exposed to hyperosmotic sodium chloride (NaCl). Atlantic salmon naturally encounter hyperosmotic NaCl concentrations as they migrate from river to ocean, and Atlantic salmon aquaculture involves an abrupt transfer of juveniles from freshwater to seawater. The central hypothesis of this research was that salmon synthesize hsps in response to dehydration and elevated ion levels associated with the transition to the marine environment.^ Metabolic protein radiolabelling experiments were performed to characterize protein induction by exposure of tissues to heat shock, NaAsO$\sb2,$ and hyperosmotic NaCl. Heat shocked branchial tissue, hepatic tissue and erythrocytes accumulated at least eight inducible proteins, most of which were common to all three tissues. Hsp70 was most rapidly induced, and the most prominently induced protein in all three tissues. The maximum rate of hsp70 synthesis was first attained in hepatic tissue, although erythrocytes exhibited the greatest relative magnitude of induction. In tissues exposed to NaAsO$\sb2,$ hsp70 was the only protein strongly induced. Induction was observed following removal of NaAsO$\sb2,$ but not during exposure. In branchial tissue and erythrocytes, accumulation of hsp70 mRNA and protein occurred during recovery from, but not during, exposure to severe salt shock. A 54kDa osmotic shock protein (osp54) was induced in branchial tissue and erythrocytes during mild salt shock. The data suggest that synthesis of hsp70 may be an emergency response to severe salt shock, conditions which might denature proteins. Although the identity and function of osp54 are unknown, accumulation of the protein at low levels of NaCl indicate it may be involved in adaptation to elevated external ion levels. These responses have potential to be exploited for applications in aquaculture. ^

Subject Area

Biology, Cell|Biology, Animal Physiology|Agriculture, Fisheries and Aquaculture

Recommended Citation

Todd Russell Smith, "Characterization of heat- and osmotic-shock proteins in Atlantic salmon ({\it Salmo salar\/}) tissues" (1997). Dissertations and Master's Theses (Campus Access). Paper AAI9831120.
http://digitalcommons.uri.edu/dissertations/AAI9831120

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