Abstract
Neonatal dogs 2 to 18 days had volume expansion (VE) with either NaCl (n=7) or NaHC03 (n=8) to determine the role of the anion in VE natriuresis. In VE with NaCl, Fractional Excretion (FE) of sodium, FENa, = 1.1%, FEK = 41.8%, FECl = 3.0%, FEHCO3 = .03%. In VE with NaHCO3, plasma HCO3 was elevated (37.3 mM) and FENa = 2.8% (p<.05), FEK = 84.7% (p<.01), FECl = 0.6% (p<.01), FEHCO3 = 7.3% (p<.01). When plasma HCO3 was elevated (32.7 mM) without VE by exchange transfusion with high HCO3, low Cl blood in 15 puppies, FENa = .4%, FEHCO3 = .7%, FEK = 47.1%. Without VE in 14 puppies with normal plasma HCO3, receiving ethacrynic acid and amiloride to block Henle's Loop (HL) and distal tubular function, FENa = 27%, FEHCO3 = 2%, FEK = 30%, FECl = 37%, but with saline VE and these diuretics FENa = 55% (p<.01), FECl = 64.2% (p<.01), FEHCO3 = 2.4% (N.S.), FEK = 68% (p<.01). We conclude that without VE almost all HCO3 is reabsorbed in the proximal tubule (PT) even with high plasma HCO3. VE, due either to NaCl or NaHCO3, inhibits PT Na reabsorption, resulting in increased loads of Na, HCO3 and Cl to HL. However, with VE due to NaCl relatively more Cl and less HCO3 is delivered to HL than during VE with NaHCO3. Thus, in the saline group HL reabsorbs more Na (as Cl) than in the HCO3 group so that in the latter group, more Na is presented to the distal tubule (as HCO3), resulting in greater distal K secretion. The net effect is greater Na, K and HCO3 and less Cl excretion during VE with NaHCO3 than with NaCl.
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Lorenz, J., Kleinman, L. & Disney, T. 1519 ROLE OF THE ANION IN VOLUME EXPANSION NATRIURESIS IN NEWBORN DOGS. Pediatr Res 15 (Suppl 4), 696 (1981). https://doi.org/10.1203/00006450-198104001-01542
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DOI: https://doi.org/10.1203/00006450-198104001-01542