Salinity-dependent expression of ncc2 in opercular epithelium and gill of mummichog ( Fundulus heteroclitus )

AbstractMummichogs (Fundulus heteroclitus) can tolerate abrupt changes in environmental salinity because of their ability to rapidly adjust the activities of ionocytes in branchial and opercular epithelia. In turn, the concerted expression of sub-cellular effectors of ion transport underlies adaptive responses to fluctuating salinities. Exposure to seawater (SW) stimulates the expression of Na+/K+/2Cl− cotransporter 1 (nkcc1) andcystic fibrosis transmembrane regulator (cftr) mRNAs in support of ion extrusion by SW-type ionocytes. Given the incomplete understanding of how freshwater (FW)-type ionocytes actually operate in mummichogs, the transcriptional responses essential for ion absorption in FW environments remain unresolved. In a subset of species, a ‘fish-specific’ Na+/Cl− cotransporter denoted Ncc2 (Slc12a10) is responsible for the uptake of Na+ and Cl− across the apical surface of FW-type ionocytes. In the current study, we identified anncc2 transcript that is highly expressed in gill filaments and opercular epithelium of FW-acclimated mummichogs. Within 1  day of transfer from SW to FW,ncc2 levels in both tissues increased in parallel with reductions innkcc1 andcftr. Conversely, mummichogs transferred from FW to SW exhibited marked reductions inncc2 concurrent with increases innkcc1 andcftr. Immunohistochemical analyses employing a homologous antibody revealed apical Ncc2-immunoreactivity in Na+/K+-ATPase-immunoreactive ionocytes of FW-acclimated animals. Ou...
Source: Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology - Category: Physiology Source Type: research