Na+, K+-ATPase (α۱a and α۱b) and NKCC co-transporter genes expression in the gills of Salmo trutta caspus, parr

The effects of fish weight on salinity tolerance were studied in Caspian salmon (Salmo trutta caspius) parr. ۱۸۰ fish (all with ۲ years old but with three weights; ۵, ۱۵, ۲۵g) were selected and they reared in freshwater (FW) and brackish water (BW; ۱۳ppt salinity) for ۱۰ days. The mRNA expression of two α-subunit isoforms of Na+, K+-ATPase (α۱a and α۱b) and NKCC co-transporters were studied in their gill tissue. In all three weight groups, the mRNA levels for the α۱a isoforms decreased following BW exposure, whereas α۱b levels significantly increased in ۱۵g and ۲۵g groups. In addition, NKCC gene expression were significantly higher in the groups of BW than FW in ۱۵g and ۲۵g weights (P<۰.۰۵). The reciprocal expression of Na+, K+-ATPase isoforms (α۱a and α۱b) during salinity acclimation suggests that they may have different roles in the gill of FW and BW fishes; ion uptake in FW and ion secretion in BW. In conclusion, in the Caspian salmon, between parrs with the same age, the group with the weight of ۱۵g possesses better compatibility with BW than to other groups.  After reaching to ۲۵g, fish passed smoltification and they became more compatible with the FW environment and maybe lost its osmoregulation ability in saline or brackish water.

کلیدواژه ها:

Caspian Salmon ، Na+-K+ pump ، Osmoregulation