Immunolocalization of ion transporter proteins in spiral valve of Persian sturgeon (Acipenser persicus, Borodin, 1897) juveniles during abrupt transfer from freshwater to the Caspian Sea water

In this study, the effect of abrupt transfer from freshwater (FW) to the Caspian Sea Water (CSW, 11‰) on ion-regulation capacity of intestine spiral valve were investigated in juvenile Persian sturgeon Acipenser persicus (2.55±0.41g). Immunofluorescence localization of ion transporter proteins including Na,K+ATPase (NKA), Na,K,2Cl– (NKCC) and cystic fibrosis transmembrane conductance regulator (CFTR) were performed 10 days after abrupt transfer. Co-localization of NKA and NKCC in the cytoplasm of enterocytes for both FW- and CSW-acclimated fish indicated that these two proteins were not affected by salinity transfer. Furthermore, CFTR was also found in the cytoplasm but mostly in apical membrane of spiral intestine enterocytes. Based on the obtained results, the main function of spiral valve is nutrient absorption and indirectly has a minor role in ion regulation in juvenile Persian sturgeon. Furthermore, this organ has good physiological development condition in 2-3g fish and it prepares their ability to expose to the Caspian Sea water salinity.