Meeting Abstract

P2.138  Sunday, Jan. 5 15:30  Effects of Salinity and Cortisol on Gill Claudin-10c, -10e, -28a, -30 and Occludin in Tilapia TIPSMARK, CK*; BREVES, JP; RABENECK, DB ; TRUBITT, RT; LERNER, DT; GRAU, EG; Univ. of Arkansas, Fayetteville; Univ. of Massechusetts, Amherst; Univ. of Arkansas, Fayetteville; Univ. of Arkansas, Fayetteville; Univ. of Hawaii, Kaneohe; Univ. of Hawaii, Kaneohe tipsmark@uark.edu

In euryhaline fishes, reorganization of gill epithelia, including tight junctions, has a key role during salinity acclimation. Five tight junction proteins were identified in the gill transcriptome of tilapia; occludin and four claudin isoforms (10c, 10e, 28a and 30). Branchial expression of these genes in Mozambique tilapia was examined during acclimation to freshwater (FW) and seawater (SW) and in response to cortisol treatment in vitro. A survey of the tissue distribution showed that occludin expression was present in many tissues with high abundance in gill, intestine and kidney. The four claudin isoforms were expressed at the highest levels in gill tissue. Transfer of tilapia from FW to SW stimulated claudin-10c and -10e, while claudin-28a, -30 and occludin were highly stimulated during FW acclimation. To evaluate if cortisol could be involved in the salinity induced changes, gill filaments were incubated with cortisol in vitro. Cortisol stimulated expression of both FW and SW induced claudin isoforms and thus had a general stimulatory effect on these targets. These data suggest that claudin-10c and -10e are important during acclimation of tilapia to SW, possibly by changing paracellular permeability. Occludin and claudin-28a and -30 appear involved in reorganization of gill epithelium during FW acclimation.