| Summary: | The European eel (Anguilla anguilla) can survive in both freshwater (FW) and seawater (SW) environments with only minor changes in the osmolality of body fluids. A microarray technique used to screen for differential gene expression following transfer from FW to SW highlighted a group of genes related to the synthesis and transport of solutes known to act as osmolytes in mammalian cells. One gene associated with the production of one such osmolyte, inositol, is myo‐inositol monophosphatase (IMPA1). Northern blot, qPCR, Western blotting and immunohistological analyses were used to compare the expression of IMPA1 in the gill and kidney as fish move between FW and SW environments. After 2 days acclimation to SW, 1.9‐ and 2.5‐fold increases in IMPA1 mRNA expression were found in kidney and gill respectively and these levels increased further to 4.9‐ and 3.4‐fold respectively, 5 months after SW transfer. IMPA1 protein expression was up‐regulated fold in the gill following SW transfer, however, no significant changes in protein abundance were detected in the kidney. Preliminary immunohistological studies have revealed that IMPA1 is expressed in most cells within the gill and especially within chondrocytes found within the branchial arch and primary filaments. Our studies have indicated a potential role for IMPA1, and the osmolyte inositol, in salinity adaptation in the European eel.
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