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

Horng JL, Chao PL, Chen PY, Shih TH, Lin LY - PLoS ONE (2015)

Bottom Line: 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.Results from this study support our hypothesis and provide in vivo evidence of the physiological role of AQP1 in CO2 transport.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.

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.

No MeSH data available.


Related in: MedlinePlus

The proposed role of AQP1a.1 in acid-secreting HR cells of zebrafish [modified from 13, 14].Refer to the text for detail. AQP1, aquaporin 1a.1; AE1, anion exchanger 1b; CA2, carbonic anhydrase 2; HA, H+-ATPase; NHE3, Na+/H+ exchanger 3; Rhcg1, Rhesus C glycoprotein 1.
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pone.0136440.g007: The proposed role of AQP1a.1 in acid-secreting HR cells of zebrafish [modified from 13, 14].Refer to the text for detail. AQP1, aquaporin 1a.1; AE1, anion exchanger 1b; CA2, carbonic anhydrase 2; HA, H+-ATPase; NHE3, Na+/H+ exchanger 3; Rhcg1, Rhesus C glycoprotein 1.

Mentions: An acid secretion mechanism similar to that found in mammalian kidney was found in fish gill/skin ionocytes [42, 43]. In the zebrafish, HR cells are the major subtype of ionocytes for H+ secretion and HCO3− reclamation, and H2O and CO2 are generally believed to be the major source for generating H+ and HCO3− [14, 17, 29]. The expression of AQP1a.1 by HR cells was thus hypothesized to provide higher permeability of cell membranes to CO2 and thus increase the production of H+ and HCO3− in HR cells. This hypothesis is supported by the present results that knockdown of AQP1a.1 and PCMB treatment suppressed acid secretion of embryos (Figs 4 and 5). The model of acid secretion by HR cells is illustrated in Fig 7 [modified from 13, 14]. AQP1a.1 in the basolateral membrane can permeabilize and increase CO2 supply intracellularly, therefore carbonic anhydrase (CA2) can generate H+ and HCO3− to supply H+ for the apical H+-ATPase and Na+/H+ exchanger (NHE3) to produce acid secretion. The HCO3− would thus be transported to the inner environment through the basolateral AE1b of HR cell.


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

Horng JL, Chao PL, Chen PY, Shih TH, Lin LY - PLoS ONE (2015)

The proposed role of AQP1a.1 in acid-secreting HR cells of zebrafish [modified from 13, 14].Refer to the text for detail. AQP1, aquaporin 1a.1; AE1, anion exchanger 1b; CA2, carbonic anhydrase 2; HA, H+-ATPase; NHE3, Na+/H+ exchanger 3; Rhcg1, Rhesus C glycoprotein 1.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4546062&req=5

pone.0136440.g007: The proposed role of AQP1a.1 in acid-secreting HR cells of zebrafish [modified from 13, 14].Refer to the text for detail. AQP1, aquaporin 1a.1; AE1, anion exchanger 1b; CA2, carbonic anhydrase 2; HA, H+-ATPase; NHE3, Na+/H+ exchanger 3; Rhcg1, Rhesus C glycoprotein 1.
Mentions: An acid secretion mechanism similar to that found in mammalian kidney was found in fish gill/skin ionocytes [42, 43]. In the zebrafish, HR cells are the major subtype of ionocytes for H+ secretion and HCO3− reclamation, and H2O and CO2 are generally believed to be the major source for generating H+ and HCO3− [14, 17, 29]. The expression of AQP1a.1 by HR cells was thus hypothesized to provide higher permeability of cell membranes to CO2 and thus increase the production of H+ and HCO3− in HR cells. This hypothesis is supported by the present results that knockdown of AQP1a.1 and PCMB treatment suppressed acid secretion of embryos (Figs 4 and 5). The model of acid secretion by HR cells is illustrated in Fig 7 [modified from 13, 14]. AQP1a.1 in the basolateral membrane can permeabilize and increase CO2 supply intracellularly, therefore carbonic anhydrase (CA2) can generate H+ and HCO3− to supply H+ for the apical H+-ATPase and Na+/H+ exchanger (NHE3) to produce acid secretion. The HCO3− would thus be transported to the inner environment through the basolateral AE1b of HR cell.

Bottom Line: 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.Results from this study support our hypothesis and provide in vivo evidence of the physiological role of AQP1 in CO2 transport.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.

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.

No MeSH data available.


Related in: MedlinePlus