Rhcg1 and NHE3b are involved in ammonium-dependent sodium uptake by zebrafish larvae acclimated to low-sodium water

2012 ◽  
Vol 302 (1) ◽  
pp. R84-R93 ◽  
Author(s):  
Tin-Han Shih ◽  
Jiun-Lin Horng ◽  
Sian-Tai Liu ◽  
Pung-Pung Hwang ◽  
Li-Yih Lin
Keyword(s):  
Yolk Sac ◽  
Ion Selective Electrode ◽  
Loss Of Function ◽  
Selective Electrode ◽  
Uptake Mechanism ◽  
Sodium Uptake ◽  
Zebrafish Larvae ◽  
Low Sodium ◽  
Morpholino Oligonucleotides ◽  
Electrode Technique

To investigate whether Na+ uptake by zebrafish is dependent on NH4+ excretion, a scanning ion-selective electrode technique was applied to measure Na+ and NH4+ gradients at the yolk-sac surface of zebrafish larvae. Low-Na+ acclimation induced an inward Na+ gradient (uptake), and a combination of low Na+ and high NH4+ induced a larger inward Na+ gradient. When measuring the ionic gradients, raising the external NH4+ level (5 mM) blocked NH4+ excretion and Na+ uptake; in contrast, raising the external Na+ level (10 mM) simultaneously enhanced Na+ uptake and NH4+ excretion. The addition of MOPS buffer (5 mM), which is known to block NH4+ excretion, also suppressed Na+ uptake. These results showed that Na+ uptake and NH4+ excretion by larval skin are associated when ambient Na+ level is low. Knockdown of Rhcg1 translation with morpholino-oligonucleotides decreased both NH4+ excretion and Na+ uptake by the skin and Na+ content of whole larvae. Knockdown of nhe3b translation or inhibitor (5-ethylisopropyl amiloride) treatment also decreased both the NH4+ excretion and Na+ uptake. This study provides loss-of-function evidence for the involvement of Rhcg1 and NHE3b in the ammonium-dependent Na+ uptake mechanism in zebrafish larvae subjected to low-Na+ water.

Ammonia excretion by the skin of zebrafish (Danio rerio) larvae

2008 ◽  
Vol 295 (6) ◽  
pp. C1625-C1632 ◽  
Author(s):  
Tin-Han Shih ◽  
Jiun-Lin Horng ◽  
Pung-Pung Hwang ◽  
Li-Yih Lin
Keyword(s):  
Direct Evidence ◽  
Ammonia Excretion ◽  
Bafilomycin A1 ◽  
Selective Electrode ◽  
Zebrafish Larvae ◽  
Trapping Mechanism ◽  
Morpholino Oligonucleotides ◽  
Electrode Technique ◽  
External Ph ◽  
Freshwater Teleosts

The mechanism of ammonia excretion in freshwater teleosts is not well understood. In this study, scanning ion-selective electrode technique was applied to measure H+ and NH4+ fluxes in specific cells on the skin of zebrafish larvae. NH4+ extrusion was relatively high in H+ pump-rich cells, which were identified as the H+-secreting ionocyte in zebrafish. Minor NH4+ extrusion was also detected in keratinocytes and other types of ionocytes in larval skin. NH4+ extrusion from the skin was tightly linked to acid secretion. Increases in the external pH and buffer concentration (5 mM MOPS) diminished H+ and NH4+ gradients at the larval surface. Moreover, coupled decreases in NH4+ and H+ extrusion were found in larvae treated with an H+-pump inhibitor (bafilomycin A1) or H+-pump gene ( atp6v1a) knockdown. Knockdown of Rhcg1 with morpholino-oligonucleotides also decreased NH4+ excretion. This study demonstrates ammonia excretion in epithelial cells of larval skin through an acid-trapping mechanism, and it provides direct evidence for the involvement of the H+ pump and an Rh glycoprotein (Rhcg1) in ammonia excretion.

Sodium ion binding in human serum.

1982 ◽  
Vol 28 (3) ◽  
pp. 449-452 ◽  
Author(s):  
T R Kissel ◽  
J R Sandifer ◽  
N Zumbulyadis
Keyword(s):  
Standard Addition ◽  
Sodium Ion ◽  
Ion Selective Electrode ◽  
Ion Selective Electrodes ◽  
Ion Binding ◽  
Selective Electrode ◽  
Titration Method ◽  
Low Sodium ◽  
Human Sera ◽  
Sodium Binding

Abstract The amount of sodium ion binding in human sera and in dialyzed human sera was estimated from standard-addition titrations with an ion-selective electrode and from measurements of 23Na nuclear magnetic resonance (NMR) linewidth. For the untreated sera, maximum binding was 1% (1.4 mmol/L) as indicated by NMR; virtually no binding was found via the titration method. For dialyzed sera with low-sodium, normal-protein content, NMR indicated that sodium binding was less than 1.3% (0.14 mmol/L). The same dialyzed fluid analyzed with ion-selective electrodes shows no sodium binding, within the limits of experimental error (+/- 4%). Sodium ion binding to serum protein thus contributes only minimally to differences in sodium measurements observed between the direct (undiluted) ion-selective electrode and flame-photometric methods.

Functional plasticity of mitochondrion-rich cells in the skin of euryhaline medaka larvae (Oryzias latipes) subjected to salinity changes

2011 ◽  
Vol 300 (4) ◽  
pp. R858-R868 ◽  
Author(s):  
Wan-Ping Shen ◽  
Jiun-Lin Horng ◽  
Li-Yih Lin
Keyword(s):  
Oryzias Latipes ◽  
Yolk Sac ◽  
Accessory Cell ◽  
Functional Plasticity ◽  
Selective Electrode ◽  
Noninvasive Technique ◽  
Salinity Changes ◽  
External Salinity ◽  
Electrode Technique ◽  
Apical Opening

A noninvasive technique, the scanning ion-selective electrode technique (SIET) was applied to measure Na+ and Cl− transport by the yolk-sac skin and individual mitochondrion-rich cells (MRCs) in intact medaka larvae ( Oryzias latipes ). In seawater (SW)-acclimated larvae, significant outward Na+ and Cl− gradients were measured at the yolk-sac surface, indicating secretions of Na+ and Cl− from the yolk-sac skin. With Na+ pump immunostaining and microscopic observation, two groups of MRCs were identified on the yolk-sac skin of SW-larvae. These were single MRCs (s-MRCs), which do not have an accompanying accessory cell (AC), and multicellular complex MRCs (mc-MRCs), which usually consist of an MRC and an accompanying AC. The percentage of mc-MRC was ∼60% in 30 parts per thousand of SW, and it decreased with the decrease of external salinity. By serial SIET probing over the surface of the MRCs and adjacent keratinocytes (KCs), significant outward fluxes of Na+ and Cl− were detected at the apical opening (membrane) of mc-MRCs, whereas only outward Cl− flux, but not Na+ flux, was detected at s-MRCs. Treatment with 100 μM ouabain or bumetanide effectively blocked the Na+ and Cl− secretion. Following freshwater (FW) to SW transfer, Na+ and Cl− secretions by the yolk-sac skin were fully developed in 5 h and 2 h, respectively. In contrast, both Na+ and Cl− secretions downregulated rapidly after SW to FW transfer. Sequential probing at individual MRCs found that Na+ and Cl− secretions declined dramatically after SW to FW transfer and Na+/Cl− uptake was detected at the same s-MRCs and mc-MRCs after 5 h. This study provides evidence demonstrating that ACs are required for Na+ excretion and MRCs possess a functional plasticity in changing from a Na+/Cl−-secreting cell to a Na+/Cl−-absorbing cell.

Sign in / Sign up

Export Citation Format

Share Document