| Tetraspan transmembrane tight junction (TJ) proteins claudins are key players in regulating paracellular epithelial "tightness". In the gill of the euryhaline puffer fish Tetraodon nigroviridis ( Tetraodon) abundance of 12 claudin genes (Tnc1dn) differ between freshwater (FW)- and seawater (SW)-acclimated fish. However, the heterogeneous nature of the gill confounds the specific role(s) of TJ proteins in this tissue. In the present study Tetraodon primary cultured gill epithelia on solid support and permeable membrane "inserts" were developed. These in vitro gill epithelia are composed exclusively of pavement cells (PVCs). Subsequent utilization of the puffer fish gill models introduces evidence for (1) the cell-specific localization of claudin in fish gill epithelia, and (2) significant heterogeneous response of select Tncldn to the osmoregulatory hormone cortisol. Furthermore, these novel preparations have allowed the molecular physiology and permeability properties of the PVC TJ complex to be observed for the first time following in vitro SW exposure. Taken together, primary cultured gill epithelia derived from Tetraodon provide a suitable research model to better understand junctional relationships between gill epithelial cells (i.e. PVCs). |
