TY - JOUR
T1 - Collecting duct-specific Rh C glycoprotein deletion alters basal and acidosis-stimulated renal ammonia excretion
AU - Lee, Hyun Wook
AU - Verlander, Jill W.
AU - Bishop, Jesse M.
AU - Igarashi, Peter
AU - Handlogten, Mary E.
AU - Weiner, I. David
PY - 2009/6
Y1 - 2009/6
N2 - NH3 movement across plasma membranes has traditionally been ascribed to passive, lipidphase diffusion. However, ammonia-specific transporters, Mep/Amt proteins, are present in primitive organisms and mammals express orthologs of Mep/Amt proteins, the Rh glycoproteins. These findings suggest that the mechanisms of NH3 movement in mammalian tissues should be reexamined. Rh C glycoprotein (Rhcg) is expressed in the collecting duct, where NH3 secretion is necessary for both basal and acidosis-stimulated ammonia transport. To determine whether the collecting duct secretes NH3 via Rhcg or via lipid-phase diffusion, we generated mice with collecting duct-specific Rhcg deletion (CD-KO). CD-KO mice had loxP sites flanking exons 5 and 9 of the Rhcg gene (Rhcgfl/fl) and expressed Cre-recombinase under control of the Ksp-cadherin promoter (Ksp-Cre). Control (C) mice were Rhcgfl/fl but Ksp-Cre negative. We confirmed kidney-specific genomic recombination using PCR analysis and collecting duct-specific Rhcg deletion using immunohistochemistry. Under basal conditions, urinary ammonia excretion was less in KO vs. C mice; urine pH was unchanged. After acid-loading for 7 days, CD-KO mice developed more severe metabolic acidosis than did C mice. Urinary ammonia excretion did not increase significantly on the first day of acidosis in CD-KO mice, despite an intact ability to increase urine acidification, whereas it increased significantly in C mice. On subsequent days, urinary ammonia excretion slowly increased in CD-KO mice, but was always significantly less than in C mice. We conclude that collecting duct Rhcg expression contributes to both basal and acidosis-stimulated renal ammonia excretion, indicating that collecting duct ammonia secretion is, at least in part, mediated by Rhcg and not solely by lipid diffusion.
AB - NH3 movement across plasma membranes has traditionally been ascribed to passive, lipidphase diffusion. However, ammonia-specific transporters, Mep/Amt proteins, are present in primitive organisms and mammals express orthologs of Mep/Amt proteins, the Rh glycoproteins. These findings suggest that the mechanisms of NH3 movement in mammalian tissues should be reexamined. Rh C glycoprotein (Rhcg) is expressed in the collecting duct, where NH3 secretion is necessary for both basal and acidosis-stimulated ammonia transport. To determine whether the collecting duct secretes NH3 via Rhcg or via lipid-phase diffusion, we generated mice with collecting duct-specific Rhcg deletion (CD-KO). CD-KO mice had loxP sites flanking exons 5 and 9 of the Rhcg gene (Rhcgfl/fl) and expressed Cre-recombinase under control of the Ksp-cadherin promoter (Ksp-Cre). Control (C) mice were Rhcgfl/fl but Ksp-Cre negative. We confirmed kidney-specific genomic recombination using PCR analysis and collecting duct-specific Rhcg deletion using immunohistochemistry. Under basal conditions, urinary ammonia excretion was less in KO vs. C mice; urine pH was unchanged. After acid-loading for 7 days, CD-KO mice developed more severe metabolic acidosis than did C mice. Urinary ammonia excretion did not increase significantly on the first day of acidosis in CD-KO mice, despite an intact ability to increase urine acidification, whereas it increased significantly in C mice. On subsequent days, urinary ammonia excretion slowly increased in CD-KO mice, but was always significantly less than in C mice. We conclude that collecting duct Rhcg expression contributes to both basal and acidosis-stimulated renal ammonia excretion, indicating that collecting duct ammonia secretion is, at least in part, mediated by Rhcg and not solely by lipid diffusion.
KW - Acid-base
KW - NH movement
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U2 - 10.1152/ajprenal.90667.2008
DO - 10.1152/ajprenal.90667.2008
M3 - Article
C2 - 19321595
AN - SCOPUS:66449116608
SN - 0363-6143
VL - 296
SP - F1364-F1375
JO - American Journal of Physiology - Cell Physiology
JF - American Journal of Physiology - Cell Physiology
IS - 6
ER -