Accueil | << 1 >> |
![]() |
Blondeau-Bidet, E., Hiroi, J., & Lorin-Nebel, C. (2019). Ion uptake pathways in European sea bass Dicentrarchus labrax. Gene, 692, 126–137.
Résumé: Ion uptake mechanisms are diverse in fish species, certainly linked to duplication events that have led to the presence of a multitude of paralogous genes. In fish, Na+ uptake involves several ion transporters expressed in different ionocyte subtypes. In the European sea bass Dicentrarchus labrax, several key transporters potentially involved in Na+ uptake have been investigated in seawater (SW) and following a 2 weeks freshwater (FW) acclimation. Using gel electrophoresis, we have shown that the Na+/H+-exchanger 3 (nhe3, slc9a3) is expressed in gills and kidney at both salinities. Quantitative realtime PCR analysis showed a significantly higher nhe3 expression in fresh water (FW) compared to SW. Its apical localization in a subset of gill ionocytes in freshwater-acclimated fish supports the role of NHE3 in Na+ uptake. Interestingly, NHE3-immunopositive cells also express basolateral Na+/K+/2Cl− cotransporter 1 (NKCC1) and are mainly localized in gill lamella. Among the three nhe2 (slc9a2) paralogs, only nhe2c shows differential branchial expression levels with higher mRNA levels in SW than in FW. The increased branchial expression of the ammonia transporter rhcg1 (Rhesus protein), nhe3 and cytoplasmic carbonic anhydrase (cac) in FW could indicate the presence of a functional coupling between ion transporters to form a Na+/NH4+ exchange complex. Acid-sensing ion channel 4 (asic4) seems not to be expressed in sea bass gills. Na+/Cl- cotransporter (ncc2a or ncc-like) is about three times more expressed in FW compared to SW suggesting coupled Na+ and Cl− uptake in a subset of gill ionocytes. Besides the main pump Na+/K+-ATPase, branchial NCC2a and NHE3 may be key players in ion uptake in sea bass following a long-term freshwater challenge.
Mots-Clés: Ion transporters; Na uptake; Ncc2; Nhe3; Osmoregulation; Teleost
|
L'Honore, T., Farcy, E., Blondeau-Bidet, E., & Lorin-Nebel, C. (2020). Inter-individual variability in freshwater tolerance is related to transcript level differences in gill and posterior kidney of European sea bass. Gene, 741, 144547.
Résumé: Acclimation to low salinities is a vital physiological challenge for euryhaline fish as the European sea bass Dicentrarchus labrax. This species undertakes seasonal migrations towards lagoons and estuaries where a wide range of salinity variations occur along the year. We have previously reported intraspecific differences in freshwater tolerance, with an average 30% mortality rate. In this study, we bring new evidence of mechanisms underlying freshwater tolerance in sea bass at gill and kidney levels. In fresh water (FW), intraspecific differences in mRNA expression levels of several ion transporters and prolactin receptors were measured. We showed that the branchial Cl-/HCO3- anion transporter (slc26a6c) was over-expressed in freshwater intolerant fish, probably as a compensatory response to low blood chloride levels and potential metabolic alkalosis. Moreover, prolactin receptor a (prlra) and Na+/Cl- cotransporter (ncc1) but not ncc-2a expression seemed to be slightly increased and highly variable between individuals in freshwater intolerant fish. In the posterior kidney, freshwater intolerant fish exhibited differential expression levels of slc26 anion transporters and Na+/K+/2Cl(-) co-transporter 1b (nkcc1b). Lower expression levels of prolactin receptors (prlra, prlrb) were measured in posterior kidney which probably contributes to the failure in ion reuptake at the kidney level. Freshwater intolerance seems to be a consequence of renal failure of ion reabsorption, which is not sufficiently compensated at the branchial level.
Mots-Clés: chloride uptake; cl-cotransporter; dicentrarchus-labrax; fish ion regulation; Freshwater acclimation; gene-expression; Intraspecific variation; Ion transporters; marine teleost; nkcc; oreochromis-mossambicus; Osmoregulation; prlr; rainbow-trout; rich cells; slc26 anion transporters; slc26a6
|
Maugars, G., Manirafasha, M. - C., Grousset, E., Boulo, V., & Lignot, J. - H. (2018). The effects of acute transfer to freshwater on ion transporters of the pharyngeal cavity in European seabass (Dicentrarchus labrax). Fish Physiol. Biochem., 44(5), 1393–1408.
Résumé: Gene expression of key ion transporters (the Na+/K+-ATPase NKA, the Na+, K+-2Cl(-) cotransporter NKCC1, and CFTR) in the gills, opercular inner epithelium, and pseudobranch of European seabass juveniles (Dicentrarchus labrax) were studied after acute transfer up to 4days from seawater (SW) to freshwater (FW). The functional remodeling of these organs was also studied. Handling stress (SW to SW transfer) rapidly induced a transcript level decrease for the three ion transporters in the gills and operculum. NKA and CFTR relative expression level were stable, but in the pseudobranch, NKCC1 transcript levels increased (up to 2.4-fold). Transfer to FW induced even more organ-specific responses. In the gills, a 1.8-fold increase for NKA transcript levels occurs within 4days post transfer with also a general decrease for CFTR and NKCC1. In the operculum, transcript levels are only slightly modified. In the pseudobranch, there is a transient NKCC1 increase followed by 0.6-fold decrease and 0.8-fold CFTR decrease. FW transfer also induced a density decrease for the opercular ionocytes and goblet cells. Therefore, gills and operculum display similar trends in SW-fish but have different responses in FW-transferred fish. Also, the pseudobranch presents contrasting response both in SW and in FW, most probably due to the high density of a cell type that is morphologically and functionally different compared to the typical gill-type ionocyte. This pseudobranch-type ionocyte could be involved in blood acid-base regulation masking a minor osmotic regulatory capacity of this organ compared to the gills.
Mots-Clés: atlantic salmon; atpase alpha-1 isoforms; branchial chloride cells; carbonic-anhydrase; Dicentrarchus labrax; gill na+/k+-atpase; Gills and extrabranchial organs; Ion transporters; k+-atpase; mitochondrion-rich cells; Osmoregulation; salinity transfer; salmon salmo-salar; seawater acclimation; Seawater to freshwater transfer; Teleost fish
|