Meeting Abstract
P1.84 Jan. 4 NKCC and CFTR in the sea-bass Dicentrarchus labrax: Ontogeny and expression according to salinity LORIN-NEBEL, Catherine; BODINIER, Charlotte; BOULO, Viviane; CHARMANTIER, Guy*; Vanderbilt University, Nashville; Universit� Montpellier II, France; Universit� Montpellier II, France; Universit� Montpellier II, France catherine.lorin-nebel@Vanderbilt.Edu
The European sea-bass is a euryhaline teleost whose most juveniles migrate from sea to lagoons or estuaries. Cellular and molecular approaches were combined to determine the functions of the cotransporter NKCC and the chloride channel CFTR in osmoregulatory organs of juvenile and early adult fish maintained in seawater and freshwater (SW, FW). Both proteins were localized by immunofluorescence. In gill ionocytes of fish in SW, NKCC and CFTR were respectively basally and apically located, suggesting ion excretion; in FW, NKCC alone was apically expressed, suggesting ion absorption. The intestine, the urinary ducts and the dorsal part of the bladder presented an apically located NKCC. Dot blots and qPCR results showed variations of the gene expression according to salinity: in particular, gill NKCC and CFTR were downregulated in FW maintained fish. The localization of both proteins was followed during the ontogeny. In prelarvae, in SW, NKCC and CFTR were present at all osmoregulatory sites, particularly in the tegumental ionocytes (but except in the kidney for CFTR). The CFTR presence in the kidney was transitory in larvae, but NKCC was detected at all developmental stages. In larvae, the density of ionocytes expressing NKCC and CFTR decreased in the skin and increased in gills. The basal vs apical cell expression of both proteins according to salinity has been recorded in juveniles. Coupled to the active ion transports effected by the Na/K ATPase, the ion exchanges mediated by NKCC and CFTR, differentially expressed and located according to salinity, result in hydromineral regulation, euryhalinity and the aptitude to migrate to varying salinity media.
