ZFIN ID: ZDB-PUB-090731-17
Evidence that SLC26 anion transporters mediate branchial chloride uptake in adult zebrafish (Danio rerio)
Perry, S.F., Vulesevic, B., Grosell, M., and Bayaa, M.
Date: 2009
Source: American journal of physiology. Regulatory, integrative and comparative physiology   297(4): R988-R997 (Journal)
Registered Authors: Perry, Steve F.
Keywords: none
MeSH Terms:
  • Acid-Base Equilibrium
  • Adaptation, Physiological
  • Age Factors
  • Animals
  • Bicarbonates/metabolism*
  • Biological Transport
  • Branchial Region/metabolism*
  • Chloride-Bicarbonate Antiporters/genetics
  • Chloride-Bicarbonate Antiporters/metabolism*
  • Chlorides/metabolism*
  • Gills/metabolism*
  • Mitochondria/metabolism
  • RNA, Messenger/metabolism
  • Zebrafish/metabolism*
  • Zebrafish Proteins/genetics
  • Zebrafish Proteins/metabolism*
PubMed: 19641131 Full text @ Am. J. Physiol. Regul. Integr. Comp. Physiol.
Experiments were performed to test the hypothesis that three members of the SLC26 anion transporter gene family (SLC26a3, A4 and A6; hereafter termed za3, za4 and za6) mediate branchial Cl(-)/HCO3(-) exchange in adult zebrafish, Danio rerio. Using real time RT-PCR, it was demonstrated that the gill expressed relatively high levels of za6 mRNA; za3 and za4 mRNA, while present, was less abundant. za4 and za6 were also expressed at relatively high levels in the kidney. The results of in situ hybridization or immunocytochemistry (za3 only) experiments performed on gill sections revealed that the SLC26 transporters were predominantly expressed on the filament epithelium (especially within the inter-lamellar regions) and to a lesser extent on the lamellar epithelium at the base of lamellae. This distribution pattern suggests that the SLC26 anion transporters are localized to mitochondrion-rich cells (ionocytes). Transferring fish to water containing low [Cl(-)] (0.02 mmol l(-1)) resulted in significant increases in branchial SLC26 mRNA expression after 5 - 10 days of exposure relative to fish raised in normal water [Cl(-)] (0.4 mmol l(-1)); transferring fish to Cl(-)-enriched water (2.0 mmol l(-1)) was without effect on mRNA levels. Transferring fish to water containing elevated levels of NaHCO3 (10 - 12.5 mmol l(-1)) caused marked increases in branchial SLC26 mRNA expression between 3 and 10 days of transfer that was associated with a significant 40% increase in Cl(-) uptake (as measured upon return to normal water after 7 days). A decrease in whole body net acid excretion (equivalent to an increase in net base excretion) in fish previously maintained in high [NaHCO3] water, concurrent with increases in Cl(-) uptake and SLC26 mRNA levels, suggests a role for these anion transporters in Cl(-) uptake and acid-base regulation owing to their Cl(-)/HCO3(-) exchange activities. Key words: mitochondrion rich cell, acid-base balance, SLC26, ionic regulation.