Na+/H+and Na+/NH4+exchange activities of zebrafish NHE3b expressed inXenopusoocytes

Ito, Yusuke; Kato, Akira; Hirata, Terumitsu; Hirose, Shigehisa; Romero, Michael F.

doi:10.1152/ajpregu.00363.2013

Cited by 33 publications

(17 citation statements)

References 46 publications

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“…This is in stark contrast to the coupling of these ions typically observed in the gills and skin (Tsui et al, 2009;Wu et al, 2010;Kumai and Perry, 2011;Shih et al, 2012;Kwong et al, 2014). Furthermore, the mRNAs of NHE2 and NHE3, the two transport proteins implicated in Na + /NH 4 + coupling (Zimmer et al, 2010;Ito et al, 2014), were below detectable levels in the kidney (note that they were detectable in goldfish gill tissue in our hands), and there was no NKA response (Table 3, Fig. 6).…”

Section: Renal Ammonia Transport Mechanismsmentioning

confidence: 57%

Physiological and molecular responses of the goldfish kidney (Carassius auratus) to metabolic acidosis, and potential mechanisms of renal ammonia transport

Lawrence

Wright

Wood

2015

Journal of Experimental Biology

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Relative to the gills, the mechanisms by which the kidney contributes to ammonia and acid-base homeostasis in fish are poorly understood. Goldfish were exposed to a low pH environment (pH 4.0, 48 h), which induced a characteristic metabolic acidosis and an increase in total plasma [ammonia] but reduced plasma ammonia partial pressure (P NH3 ). In the kidney tissue, total ammonia, lactate and intracellular pH remained unchanged. The urinary excretion rate of net base under control conditions changed to net acid excretion under low pH, with contributions from both the NH 4 + (∼30%) and titratable acidity minus bicarbonate (∼70%; TA-HCO 3 − ) components. Inorganic phosphate (P i ), urea and Na + excretion rates were also elevated while Cl − excretion rates were unchanged. Renal alanine aminotransferase activity increased under acidosis. The increase in renal ammonia excretion was due to significant increases in both the glomerular filtration and the tubular secretion rates of ammonia, with the latter accounting for ∼75% of the increase. There was also a 3.5-fold increase in the mRNA expression of renal Rhcg-b (Rhcg1) mRNA. There was no relationship between ammonia secretion and Na + reabsorption. These data indicate that increased renal ammonia secretion during acidosis is probably mediated through Rhesus (Rh) glycoproteins and occurs independently of Na + transport, in contrast to branchial and epidermal models of Na + -dependent ammonia transport in freshwater fish. Rather, we propose a model of parallel H + /NH 3 transport as the primary mechanism of renal tubular ammonia secretion that is dependent on renal amino acid catabolism.

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Section: Renal Ammonia Transport Mechanismsmentioning

confidence: 57%

Physiological and molecular responses of the goldfish kidney (Carassius auratus) to metabolic acidosis, and potential mechanisms of renal ammonia transport

Lawrence

Wright

Wood

2015

Journal of Experimental Biology

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“…The pH i , aNa i , and aCl i of oocytes were measured using H + , Na + , or Cl − ion-selective microelectrodes prepared with H + ionophore I-mixture B ionselective resin (Fluka), Na + ionophore mixture A (Fluka), or Cl − ionophore I mixture A (Fluka), respectively, as described previously (40)(41)(42). The V m was measured as the difference between a KCl microelectrode and an extracellular calomel electrode.…”

Section: Methodsmentioning

confidence: 99%

Transport proteins NHA1 and NHA2 are essential for survival, but have distinct transport modalities

Chintapalli

Kato

Henderson

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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The cation/proton antiporter (CPA) family includes the well-known sodium/proton exchanger (NHE; SLC9A) family of Na + /H + exchangers, and the more recently discovered and less well understood CPA2s (SLC9B), found widely in living organisms. In Drosophila, as in humans, they are represented by two genes, Nha1 (Slc9b1) and Nha2 (Slc9b2), which are enriched and functionally significant in renal tubules. The importance of their role in organismal survival has not been investigated in animals, however. Here we show that single RNAi knockdowns of either Nha1 or Nha2 reduce survival and in combination are lethal. Knockdown of either gene alone results in up-regulation of the other, suggesting functional complementation of the two genes. Under salt stress, knockdown of either gene decreases survival, demonstrating a key role for the CPA2 family in ion homeostasis. This is specific to Na + stress; survival on K + intoxication is not affected by sodium/hydrogen antiporter (NHA) knockdown. A direct functional assay in Xenopus oocytes shows that Nha2 acts as a Na + /H + exchanger. In contrast, Nha1 expressed in Xenopus oocytes shows strong Cl − conductance and acts as a H + -Cl − cotransporter. The activity of Nha1 is inhibited by chloride-binding competitors 4,4′-diiso-thiocyano-2,2′-disulfonic acid stilbene and 4,4′-dibenzamido-2,2′-stilbenedisulphonate. Salt stress induces a massive up-regulation of NHA gene expression not in the major osmoregulatory tissues of the alimentary canal, but in the crop, cuticle, and associated tissues. Thus, it is necessary to revise the classical view of the coordination of different tissues in the coordination of the response to osmoregulatory stress.The NHA Gene Family Ionic homeostasis is essential for life and requires a significant fraction of an organism's total energy budget. Primary ion-motive ATPases provide electrochemical ion gradients to drive an array of channels, cotransporters, and antiporters. The cation/proton antiporter (CPA) family is ubiquitous and best known for the NHE, or CPA1, branch exemplified by the classical Na + /H + exchanger NHE1 (1, 2), which is a target for the potassium-sparing diuretic amiloride in the treatment of hypertension and congestive heart failure. More recently discovered are the sodium/hydrogen antiporters (NHAs), a subbranch of the CPA2 family, which is much less well understood (3, 4). Originally studied in bacteria, yeast, and plants (5, 6), this subbranch in humans includes two NHA genes in tandem: NHA1 (SLC9B1), which is testis-specific, and NHA2 (SLC9B2), which is ubiquitous (7,8).In osteoclasts, NHA2 colocalizes with the V-ATPase a3 subunit and the lysosomal marker LAMP2 (9), and resides in the plasma membrane of Madin-Darby canine kidney (MDCK) cells (7). In the pancreas, NHA2 is necessary for insulin secretion but localizes not to insulin-containing vesicles, but rather to transferrin-positive endocytic vesicles (4, 10). NHA2 also has been linked to hypertension (8). Thus, NHAs are multifunctional proteins expressed in a wide range of ...

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“…To determine the relative involvement of Na + transporters in Na + uptake, DAPI and two other Na + inhibitors -ethyl-isopropyl-amiloride (EIPA), which has a high selectivity for NHE (Ito et al, 2014;Kleyman and Cragoe, 1988) and amiloride, which inhibits both NHE and Na + channels (Kleyman and Cragoe, 1988) -were tested in low-Na + (511±25 μmol l −1 ) and ultra-lowNa + (49.5±0.5 μmol l −1 ) conditions (Fig. 2).…”

Section: Pharmacological Inhibition Of Na + Uptakementioning

confidence: 99%

The role of acid-sensing ion channels (ASICs) in epithelial Na+ uptake in adult zebrafish (Danio rerio).

Dymowska

Boyle

Schultz

et al. 2015

Journal of Experimental Biology

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Acid-sensing ion channels (ASICs) are epithelial Na + channels gated by external H + . Recently, it has been demonstrated that ASICs play a role in Na + uptake in freshwater rainbow trout. Here, we investigate the potential involvement of ASICs in Na + transport in another freshwater fish species, the zebrafish (Danio rerio). Using molecular and histological techniques we found that asic genes and the ASIC4.2 protein are expressed in the gill of adult zebrafish. Immunohistochemistry revealed that mitochondrion-rich cells positive for ASIC4.2 do not co-localize with Na + /K + -ATPase-rich cells, but co-localize with cells expressing vacuolar-type H + -ATPase. Furthermore, pharmacological inhibitors of ASIC and Na + /H + -exchanger significantly reduced uptake of Na + in adult zebrafish exposed to low-Na + media, but did not cause the same response in individuals exposed to ultra-low-Na + water. Our results suggest that in adult zebrafish ASICs play a role in branchial Na + uptake in media with low Na + concentrations and that mechanisms used for Na + uptake by zebrafish may depend on the Na + concentration in the acclimation medium.

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Na⁺/H⁺and Na⁺/NH₄⁺exchange activities of zebrafish NHE3b expressed inXenopusoocytes

Cited by 33 publications

References 46 publications

Physiological and molecular responses of the goldfish kidney (Carassius auratus) to metabolic acidosis, and potential mechanisms of renal ammonia transport

Physiological and molecular responses of the goldfish kidney (Carassius auratus) to metabolic acidosis, and potential mechanisms of renal ammonia transport

Transport proteins NHA1 and NHA2 are essential for survival, but have distinct transport modalities

The role of acid-sensing ion channels (ASICs) in epithelial Na+ uptake in adult zebrafish (Danio rerio).

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