title: The Rh complex exports ammonium from human red blood cells.
abstract: The Rh blood group system represents a major immunodominant protein complex on red blood cells (RBC). Recently, the Rh homologues RhAG and RhCG were shown to promote ammonium ion transport in yeast. In this study, we showed that also in RBC the human Rh complex functions as an exporter of ammonium ions. We measured ammonium import during the incubation of RBC in a solution containing a radiolabelled analogue of NH4Cl (14C-methyl-NH3Cl). Rhnull cells of the regulator type (expressing no Rh complex proteins) accumulated significantly higher levels (P = 0.05) of radiolabelled methyl-ammonium ions than normal RBC, at room temperature. Rhnull cells of the amorph type (expressing limited amounts of Rh complex proteins) accumulated an intermediate amount of methyl-ammonium ions. To show that decreased ammonium export contributes to its accumulation, the release of intracellular methyl-ammonium from the cells was measured over time. In 30 s, normal RBC released 87% of the intracellular methyl-ammonium ions, whereas Rhnull cells of the regulator type released only 46%. We conclude that the Rh complex is involved in the export of ammonium from RBC.
authors.affiliation: Laboratory for Transfusion Science, Bloodbank Rotterdam, Rotterdam, the Netherlands.
authors.forename: Mirte B
authors.initials: MB
authors.lastname: Hemker
authors.forename: Goedele
authors.initials: G
authors.lastname: Cheroutre
authors.forename: Rob
authors.initials: R
authors.lastname: van Zwieten
authors.forename: Petra A
authors.initials: PA
authors.lastname: Maaskant-van Wijk
authors.forename: Dirk
authors.initials: D
authors.lastname: Roos
authors.forename: Johannes A
authors.initials: JA
authors.lastname: Loos
authors.forename: C Ellen
authors.initials: CE
authors.lastname: van der Schoot
authors.forename: Albert E G Kr
authors.initials: AE
authors.lastname: von dem Borne
mesh_terms: D001596:Benzylamines / Q000378:metabolism; D001692:Biological Transport; D002250:Carbon Radioisotopes / Q000378:metabolism; D002478:Cells, Cultured; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D007501:Iron / Q000378:metabolism*; D008744:Methylamines / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D012204:Rh-Hr Blood-Group System / Q000378:metabolism*; D014508:Urea / Q000378:metabolism
chemical_list: D001596:Benzylamines; D002250:Carbon Radioisotopes; D008744:Methylamines; D000644:Quaternary Ammonium Compounds; D012204:Rh-Hr Blood-Group System; D014508:Urea; C030796:benzylamine; C027451:methylamine; D007501:Iron