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Compensatory regulation of Na+ absorption by Na+/H+ exchanger and Na+-Cl- cotransporter in zebrafish (Danio rerio).

Chang WJ, Wang YF, Hu HJ, Wang JH, Lee TH, Hwang PP - Front. Zool. (2013)

Bottom Line: Environmental acid stress suppressed nhe3b expression in HR cells and decreased Na+ content, which was followed by up-regulation of NCC cells accompanied by recovery of Na+ content.Moreover, knockdown of ncc resulted in a significant decrease of Na+ content in acid-acclimated zebrafish.These results provide evidence that HR and NCC cells exhibit functional redundancy in Na+ absorption, similar to the regulatory mechanisms in mammalian kidney, and suggest this functional redundancy is a critical strategy used by zebrafish to survive in a harsh environment that disturbs body fluid Na+ homeostasis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan. pphwang@gate.sinica.edu.tw.

ABSTRACT

Introduction: In mammals, internal Na+ homeostasis is maintained through Na+ reabsorption via a variety of Na+ transport proteins with mutually compensating functions, which are expressed in different segments of the nephrons. In zebrafish, Na+ homeostasis is achieved mainly through the skin/gill ionocytes, namely Na+/H+ exchanger (NHE3b)-expressing H+-ATPase rich (HR) cells and Na+-Cl- cotransporter (NCC)-expressing NCC cells, which are functionally homologous to mammalian proximal and distal convoluted tubular cells, respectively. The present study aimed to investigate whether or not the functions of HR and NCC ionocytes are differentially regulated to compensate for disruptions of internal Na+ homeostasis and if the cell differentiation of the ionocytes is involved in this regulation pathway.

Results: Translational knockdown of ncc caused an increase in HR cell number and a resulting augmentation of Na+ uptake in zebrafish larvae, while NHE3b loss-of-function caused an increase in NCC cell number with a concomitant recovery of Na+ absorption. Environmental acid stress suppressed nhe3b expression in HR cells and decreased Na+ content, which was followed by up-regulation of NCC cells accompanied by recovery of Na+ content. Moreover, knockdown of ncc resulted in a significant decrease of Na+ content in acid-acclimated zebrafish.

Conclusions: These results provide evidence that HR and NCC cells exhibit functional redundancy in Na+ absorption, similar to the regulatory mechanisms in mammalian kidney, and suggest this functional redundancy is a critical strategy used by zebrafish to survive in a harsh environment that disturbs body fluid Na+ homeostasis.

No MeSH data available.


Related in: MedlinePlus

Down-regulation of nhe3b in gills under acid stress. (A): Expression of nhe3b mRNA in gills treated with control pH7 FW (white bars) or acidic pH4 FW (gray bars) for the indicated days. Mean ± SD (n = 6). *p < 0.05 (Student’s t-test). (B-E): Immunostaining images of H+-ATPase (H-pump) and NHE3b in gills from adult zebrafish maintained in pH7 FW (B, D) or pH4 FW (C, E) for 7 d. Arrow, NCC or NHE3b signal; arrow head, weaker NHE3b signal. Scale bar = 100 μm.
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Figure 4: Down-regulation of nhe3b in gills under acid stress. (A): Expression of nhe3b mRNA in gills treated with control pH7 FW (white bars) or acidic pH4 FW (gray bars) for the indicated days. Mean ± SD (n = 6). *p < 0.05 (Student’s t-test). (B-E): Immunostaining images of H+-ATPase (H-pump) and NHE3b in gills from adult zebrafish maintained in pH7 FW (B, D) or pH4 FW (C, E) for 7 d. Arrow, NCC or NHE3b signal; arrow head, weaker NHE3b signal. Scale bar = 100 μm.

Mentions: Next, we investigated compensation of Na+ uptake function during acclimation to an acidic environment. The majority of nhe3b mRNA expression in adult gills was suppressed during acclimation to an acidic environment (Figure 4A). Immunostaining revealed that HR cells were markedly increased, while NHE3b signals were significantly decreased, after acid acclimation (Figure 4B-E). Therefore, nhe3b mRNA and NHE3b protein are both decreased in zebrafish gills after acid treatment.


Compensatory regulation of Na+ absorption by Na+/H+ exchanger and Na+-Cl- cotransporter in zebrafish (Danio rerio).

Chang WJ, Wang YF, Hu HJ, Wang JH, Lee TH, Hwang PP - Front. Zool. (2013)

Down-regulation of nhe3b in gills under acid stress. (A): Expression of nhe3b mRNA in gills treated with control pH7 FW (white bars) or acidic pH4 FW (gray bars) for the indicated days. Mean ± SD (n = 6). *p < 0.05 (Student’s t-test). (B-E): Immunostaining images of H+-ATPase (H-pump) and NHE3b in gills from adult zebrafish maintained in pH7 FW (B, D) or pH4 FW (C, E) for 7 d. Arrow, NCC or NHE3b signal; arrow head, weaker NHE3b signal. Scale bar = 100 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC3750650&req=5

Figure 4: Down-regulation of nhe3b in gills under acid stress. (A): Expression of nhe3b mRNA in gills treated with control pH7 FW (white bars) or acidic pH4 FW (gray bars) for the indicated days. Mean ± SD (n = 6). *p < 0.05 (Student’s t-test). (B-E): Immunostaining images of H+-ATPase (H-pump) and NHE3b in gills from adult zebrafish maintained in pH7 FW (B, D) or pH4 FW (C, E) for 7 d. Arrow, NCC or NHE3b signal; arrow head, weaker NHE3b signal. Scale bar = 100 μm.
Mentions: Next, we investigated compensation of Na+ uptake function during acclimation to an acidic environment. The majority of nhe3b mRNA expression in adult gills was suppressed during acclimation to an acidic environment (Figure 4A). Immunostaining revealed that HR cells were markedly increased, while NHE3b signals were significantly decreased, after acid acclimation (Figure 4B-E). Therefore, nhe3b mRNA and NHE3b protein are both decreased in zebrafish gills after acid treatment.

Bottom Line: Environmental acid stress suppressed nhe3b expression in HR cells and decreased Na+ content, which was followed by up-regulation of NCC cells accompanied by recovery of Na+ content.Moreover, knockdown of ncc resulted in a significant decrease of Na+ content in acid-acclimated zebrafish.These results provide evidence that HR and NCC cells exhibit functional redundancy in Na+ absorption, similar to the regulatory mechanisms in mammalian kidney, and suggest this functional redundancy is a critical strategy used by zebrafish to survive in a harsh environment that disturbs body fluid Na+ homeostasis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan. pphwang@gate.sinica.edu.tw.

ABSTRACT

Introduction: In mammals, internal Na+ homeostasis is maintained through Na+ reabsorption via a variety of Na+ transport proteins with mutually compensating functions, which are expressed in different segments of the nephrons. In zebrafish, Na+ homeostasis is achieved mainly through the skin/gill ionocytes, namely Na+/H+ exchanger (NHE3b)-expressing H+-ATPase rich (HR) cells and Na+-Cl- cotransporter (NCC)-expressing NCC cells, which are functionally homologous to mammalian proximal and distal convoluted tubular cells, respectively. The present study aimed to investigate whether or not the functions of HR and NCC ionocytes are differentially regulated to compensate for disruptions of internal Na+ homeostasis and if the cell differentiation of the ionocytes is involved in this regulation pathway.

Results: Translational knockdown of ncc caused an increase in HR cell number and a resulting augmentation of Na+ uptake in zebrafish larvae, while NHE3b loss-of-function caused an increase in NCC cell number with a concomitant recovery of Na+ absorption. Environmental acid stress suppressed nhe3b expression in HR cells and decreased Na+ content, which was followed by up-regulation of NCC cells accompanied by recovery of Na+ content. Moreover, knockdown of ncc resulted in a significant decrease of Na+ content in acid-acclimated zebrafish.

Conclusions: These results provide evidence that HR and NCC cells exhibit functional redundancy in Na+ absorption, similar to the regulatory mechanisms in mammalian kidney, and suggest this functional redundancy is a critical strategy used by zebrafish to survive in a harsh environment that disturbs body fluid Na+ homeostasis.

No MeSH data available.


Related in: MedlinePlus