Journal
AMERICAN JOURNAL OF PHYSIOLOGY-RENAL PHYSIOLOGY
Volume 281, Issue 4, Pages F718-F727Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajprenal.2001.281.4.F718
Keywords
sodium absorption; sodium/hydrogen exchanger; slc9a2; slc9a3
Categories
Funding
- NIDDK NIH HHS [DK-54430, DK-50594, DK-57552] Funding Source: Medline
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To study the role of Na+/H+ exchanger isoform 2 (NHE2) and isoform 3 (NHE3) in sodium-fluid volume homeostasis and renal Na+ conservation, mice with Nhe2 (Nhe2(-/-)) and/or Nhe3 (Nhe3(-/-)) null mutations were fed a Na+-restrieted diet, and urinary Na excretion, blood pressure, systemic acid-base and electrolyte status, and renal function were analyzed. Na+-restricted Nhe2(-/-) mice, on either a wild-type or Nhe3 heterozygous mutant (Nhe3(+/-)) background, did not exhibit excess urinary Na+ excretion. After 15 days of Na+ restriction, blood pressure, fractional excretion of Na+, and the glomerular filtration rate (GFR) of Nhe2(-/-)Nhe3(+/-) mice were similar to those of Nhe2(+/+) and Nhe3(+/-) mice, and no metabolic disturbances were observed. Nhe3(-/-) mice maintained on a Na+-restricted diet for 3 days exhibited hyperkalemia, urinary salt wasting, acidosis, sharply reduced blood pressure and GFR, and evidence of hypovolemic shock. These results negate the hypothesis that NHE2 plays an important renal function in sodium-fluid volume homeostasis; however, they demonstrate that NHE3 is critical for systemic electrolyte, acid-base, and fluid volume homeostasis during dietary Na+ restriction and that its absence leads to renal salt wasting.
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