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Assessing the role of the acid-sensing ion channel ASIC4b in sodium uptake by larval zebrafish.

Comp. Biochem. Physiol., Part A Mol. Integr. Physiol.2018 Dec;226:1-10. Epub 2018 Jun 15
Alex M Zimmer 1 , Agnieszka K Dymowska 2 , Yusuke Kumai 3 , Greg G Goss 4 , Steve F Perry 3 , Raymond W M Kwong 5
Alex M Zimmer 1 , Agnieszka K Dymowska 2 , Yusuke Kumai 3 , Greg G Goss 4 , Steve F Perry 3 , Raymond W M Kwong 5
+ et al

[No authors listed]

Author information
  • 1 Department of Biology, University of Ottawa, Ottawa, Ontario, Canada. Electronic address: azimmer@uottawa.ca.
  • 2 Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada; College of Marine Sciences, University of South Florida, Saint Petersburg, USA.
  • 3 Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.
  • 4 Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.
  • 5 Department of Biology, University of Ottawa, Ottawa, Ontario, Canada; Department of Biology, York University, Toronto, Ontario, Canada.

摘要


Na+ uptake in larval zebrafish (Danio rerio) is coordinated by three mechanisms: Na+/H+-exchanger 3b (NHE3b) expressed in H+-ATPase-rich (HR) cells, an unidentified Na+ channel coupled to electrogenic H+-ATPase expressed in HR cells, and Na+-Cl--cotransporter (NCC) expressed in NCC cells. Recently, acid-sensing ion channels (ASICs) were proposed to be the putative Na+ channel involved in H+-ATPase-mediated Na+ uptake in adult zebrafish and rainbow trout. In the present study, we hypothesized that ASICs also play this role in Na+ uptake in larval zebrafish. In support of this hypothesis, immunohistochemical analyses revealed that ASIC4b was expressed in HR cells on the yolk sac skin at 4 days post-fertilization (dpf). However, neither treatment with the ASIC-specific blocker 4,6-diamidino-2-phenylindole (DAPI) nor morpholino knockdown of ASIC4b reduced Na+ uptake in circumneutral conditions at 4 dpf. However, because ASIC4b knockdown led to significant increases in the mRNA expression of nhe3b and ncc and a significant increase in HR cell density, it is possible that Na+ influx was sustained by increased participation of non-ASIC4b pathways. Moreover, when fish were reared in acidic water (pH = 4), ASIC4b knockdown led to a stimulation of Na+ uptake at 3 and 4 dpf, results which also were inconsistent with an essential role for ASIC-mediated Na+ uptake, even under conditions known to constrain Na+ uptake via NHE3b. Thus, while ASIC4b clearly is expressed in HR cells, the current functional experiments cannot confirm its involvement in Na+ uptake in larval zebrafish.

KEYWORDS: ASIC4b, Danio rerio, H(+)-ATPase rich cells, Ion regulation, Ionocytes, Sodium uptake