title: Hypophosphaturia impairs the renal defense against metabolic acidosis.
abstract: It is known that Pi normally provides the major source of non-NH3 urinary buffer and that Pi-buffered renal H+ excretion (titratable acidity, TA) accounts for a large fraction of daily renal net acid excretion (NAE). Whether the presence of luminal non-NH3 buffers is a prerequisite to normal renal regulation of systemic acid-base equilibrium under any conditions has not been investigated. Accordingly, I investigated whether chronic renal regulation of plasma (p) [HCO3] might be impaired under conditions of normophosphatemic hypophosphaturia (NHP) produced by short-term dietary Pi restriction. During a steady-state of HCl-induced acidosis in NaCl-replete NHP dogs (group 1A, N = 6), [HCO3-]p averaged 14.1 +/- 0.6 mEq/liter and arterial (a) [H+] averaged 54 +/- 2 nEq/liter. Substitution K+ 2.5 mEq/kg as neutral Pi for equivalent dietary KCl for 7 to 8 days resulted in significant amelioration of acidosis (delta [HCO3-]p + 2.2 +/- 0.5 mEq/liter, P less than 0.01; delta [H+]a -6 +/- 2 nEq/liter, P less than 0.01) in association with a cumulative increment (sigma delta) in TA excretion (+ 103 mEq, P less than 0.001) and NAE (+ 22 mEq). To investigate whether Pi-induced amelioration of acidosis was related to enhanced urinary buffer capacity, an additional group (group 1B, N = 5) with NHP and chronic HCl acidosis was administered the non-Pi buffer, neutral creatinine (5.0 mmoles/kg daily). As with Pi, acidosis was ameliorated by creatinine administration and sigma delta NAE increased.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000136:Acid-Base Equilibrium / Q000187:drug effects; D000138:Acidosis / Q000503:physiopathology*; D000818:Animals; D001639:Bicarbonates / Q000097:blood; D002712:Chlorides / Q000008:administration & dosage; D003404:Creatinine / Q000008:administration & dosage; D004195:Disease Models, Animal; D004285:Dogs; D005260:Female; D006851:Hydrochloric Acid / Q000008:administration & dosage / Q000652:urine; D007668:Kidney / Q000503:physiopathology*; D010710:Phosphates / Q000008:administration & dosage / Q000097:blood / Q000652:urine*; D011189:Potassium Chloride / Q000652:urine; D012965:Sodium Chloride / Q000652:urine
chemical_list: D001639:Bicarbonates; D002712:Chlorides; D010710:Phosphates; D012965:Sodium Chloride; D011189:Potassium Chloride; D003404:Creatinine; D006851:Hydrochloric Acid