Aquaporin 1 Is Involved in Acid Secretion by Ionocytes of Zebrafish Embryos through Facilitating CO2 Transport

PLoS One. 2015 Aug 19;10(8):e0136440. doi: 10.1371/journal.pone.0136440. eCollection 2015.

Abstract

Mammalian aquaporin 1 (AQP1) is well known to function as a membrane channel for H2O and CO2 transport. Zebrafish AQP1a.1 (the homologue of mammalian AQP1) was recently identified in ionocytes of embryos; however its role in ionocytes is still unclear. In this study, we hypothesized that zebrafish AQP1a.1 is involved in the acid secretion by ionocytes through facilitating H2O and CO2 diffusion. A real-time PCR showed that mRNA levels of AQP1a.1 in embryos were induced by exposure to 1% CO2 hypercapnia for 3 days. In situ hybridization and immunohistochemistry showed that the AQP1a.1 transcript was highly expressed by acid-secreting ionocytes, i.e., H+-ATPase-rich (HR) cells. A scanning ion-selective electrode technique (SIET) was applied to analyze CO2-induced H+ secretion by individual ionocytes in embryos. H+ secretion by HR cells remarkably increased after a transient loading of CO2 (1% for 10 min). AQP1a.1 knockdown with morpholino oligonucleotides decreased the H+ secretion of HR cells by about half and limited the CO2 stimulated increase. In addition, exposure to an AQP inhibitor (PCMB) for 10 min also suppressed CO2-induced H+ secretion. Results from this study support our hypothesis and provide in vivo evidence of the physiological role of AQP1 in CO2 transport.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acids / metabolism
  • Animals
  • Aquaporin 1 / antagonists & inhibitors
  • Aquaporin 1 / genetics
  • Aquaporin 1 / metabolism*
  • Carbon Dioxide / metabolism*
  • Gene Knockdown Techniques
  • Immunohistochemistry
  • In Situ Hybridization
  • Proton-Translocating ATPases / metabolism
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Real-Time Polymerase Chain Reaction
  • Skin / cytology
  • Skin / metabolism
  • Zebrafish / embryology*
  • Zebrafish / genetics
  • Zebrafish / metabolism*
  • Zebrafish Proteins / antagonists & inhibitors
  • Zebrafish Proteins / genetics
  • Zebrafish Proteins / metabolism*

Substances

  • Acids
  • RNA, Messenger
  • Zebrafish Proteins
  • Carbon Dioxide
  • Aquaporin 1
  • Proton-Translocating ATPases

Grants and funding

This study was supported by the grant (101-2311-B-003 -004 -MY3) of the Ministry of Science and Technology of Taiwan.