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Am J Physiol Cell Physiol December 1, 2015; 309 (11): C747-58.
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Mechanisms of ammonia and ammonium transport by rhesus-associated glycoproteins.

Caner T , Abdulnour-Nakhoul S , Brown K , Islam MT , Hamm LL , Nakhoul NL .

In this study we characterized ammonia and ammonium (NH3/NH4(+)) transport by the rhesus-associated (Rh) glycoproteins RhAG, Rhbg, and Rhcg expressed in Xenopus oocytes. We used ion-selective microelectrodes and two-electrode voltage clamp to measure changes in intracellular pH, surface pH, and whole cell currents induced by NH3/NH4(+) and methyl amine/ammonium (MA/MA(+)). These measurements allowed us to define signal-specific signatures to distinguish NH3 from NH4(+) transport and to determine how transport of NH3 and NH4(+) differs among RhAG, Rhbg, and Rhcg. Our data indicate that expression of Rh glycoproteins in oocytes generally enhanced NH3/NH4(+) transport and that cellular changes induced by transport of MA/MA(+) by Rh proteins were different from those induced by transport of NH3/NH4(+). Our results support the following conclusions: 1) RhAG and Rhbg transport both the ionic NH4(+) and neutral NH3 species; 2) transport of NH4(+) is electrogenic; 3) like Rhbg, RhAG transport of NH4(+) masks NH3 transport; and 4) Rhcg is likely to be a predominantly NH3 transporter, with no evidence of enhanced NH4(+) transport by this transporter. The dual role of Rh proteins as NH3 and NH4(+) transporters is a unique property and may be critical in understanding how transepithelial secretion of NH3/NH4(+) occurs in the renal collecting duct.

PubMed ID: 26354748
PMC ID: PMC4868257
Article link: Am J Physiol Cell Physiol
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: acta4 rhag rhbg rhcg

References [+] :
Ammann, Neutral carrier based hydrogen ion selective microelectrode for extra- and intracellular studies. 1982, Pubmed