Zoological Studies

Constant Muscle Water Content and Renal HSP90 Expression Reflect Osmotic Homeostasis in Euryhaline Teleosts Acclimated to Different Environmental Salinities

Cheng-Hao Tang, Ching-San Tzeng, Lie-Yueh Hwang, and Tsung-Han Lee (2009) Changes in environmental salinities trigger osmoregulatory mechanisms of euryhaline teleosts in order to maintain the plasma osmolality and water balance.  The kidneys are the osmoregulatory organ inside the body which perform ion re-absorption and water regulation.  Heat shock proteins (HSPs) are also known as stress proteins, with HSP90 as one of the major classes of HSPs essential for living eukaryotes because it is responsible for the repair and refolding of damaged proteins.  In the present study, euryhaline tilapia (Oreochromis mossambicus), spotted green pufferfish (Tetraodon nigroviridis), and milkfish (Chanos chanos), with respective primary natural habitats of freshwater lakes, estuaries, and the sea, were acclimated to fresh water (FW), brackish water (BW; 15‰ salinity), and seawater (SW; 35‰ salinity).  The muscle water content (MWC) and relative protein amounts of HSP90 in the kidneys of the 3 studied species acclimated to different salinity environments were analyzed in this study.  The MWC of these 3 euryhaline teleosts revealed no significant changes in FW, BW, and SW.  Furthermore, relative protein amounts of renal HSP90 were similar among the 3 studied species acclimated to various environments.  The physiological (MWC) and stress (HSP90) responses integrated in this study might be indicators of osmoregulatory capacity, illustrating homeostasis of the internal environments of euryhaline teleosts.