Thermal shock of salmon in vivo induces the heat shock protein hsp 70 and confers protection against osmotic shock

Salmon transferred from freshwater hatcheries to seawater netpens are subjected to osmotic shock which can disrupt biochemical processes and cause stunted growth or death. The present study aimed to determine if heat shock proteins (hsps) induced by exposure of living animals to thermal shock might confer protection against this osmotic challenge. A 66 kDa protein which cross reacted with a monoclonal antibody to mammalian hsp 70, was induced in hepatic and branchial tissue of juvenile salmon subjected to a 15 min heat shock at 26 degrees. De novo synthesis of this protein did not continue beyond the first 3 h of recovery from heat shock, but the newly synthesized protein was stable for at least 12 h. Heat shocked salmon were better able to survive a subsequent severe osmotic challenge (45 ppt). Cross protection against osmotic shock was observed only during a two month period coincident with pan-smelt transformation, when branchial Na+/K+ ATPase activity was elevated. This report is the first to demonstrate protection against osmotic challenge by heat shock in a living animal. (C) 1998 Elsevier Science B.V. All rights reserved.