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Abstract: FR-PO292

Non-Osmotic Sodium Storage Capacity in Patients with Glycosaminoglycan Alterations

Session Information

Category: Fluid and Electrolytes

  • 902 Fluid and Electrolytes: Clinical

Authors

  • Besseling, Stijn, Amsterdam Cardiovascular Sciences, Amsterdam Medical Center, University of Amsterdam, Amsterdam, Netherlands
  • Wenstedt, Eliane, Amsterdam Cardiovascular Sciences, Amsterdam Medical Center, University of Amsterdam, Amsterdam, Netherlands
  • Olde Engberink, Rik Hg, Academic Medical Center, Amsterdam, Netherlands
  • Rorije, Nienke M.G., Amsterdam Cardiovascular Sciences, Amsterdam Medical Center, University of Amsterdam, Amsterdam, Netherlands
  • Vogt, Liffert, Amsterdam Cardiovascular Sciences, Amsterdam Medical Center, University of Amsterdam, Amsterdam, Netherlands
Background

In the 2-compartment model the kidneys are believed to be solely responsible for matching Na+ intake and excretion. Recent observations that Na+ can accumulate in the body without concurrent water retention, via binding to negatively charged glycosaminoglycans (GAG), challenge this model. Type 1 diabetic (DM1) patients are characterized by acquired GAG loss while hereditary multiple exostosis (HME) patients have defective heparan sulfate GAG polymerization due to mutations in either EXT1 or EXT2 genes. We questioned whether non-osmotic sodium storage is impaired in DM1 and HME patients as compared to healthy controls (HC).

Methods

Eight DM1, 7 HME patients and 11 HC were included, all non-smoking males with normal kidney function, BMI and blood pressure. Non-osmotic storage capacity was estimated after acute infusion of 0.54±0.1L hypertonic saline (2.4±0.2%) by measuring plasma [Na+] and urinary Na+ and K+ excretion at various time points during 4-hr follow-up. We compared the observed changes in plasma [Na+] with the expected changes that were estimated by Adrogue-Madias (AM) and Nguyen-Kurtz formulas, which are based on the 2-compartment model.

Results

Maximum increase (mean (SE)) of plasma [Na+] was reached 5 minutes after infusion in all 3 groups (DM1, 5.4±0.6; HME, 4.1±0.5, HC 3.5±0.4 mmol/L). The plasma [Na+] rise 5 minutes after infusion in DM1 was significantly higher than in HC (p=.01), without differences between HC and HME patient (p=.42). The formulas poorly predicted plasma [Na+] 5 minutes after infusion, with observed changes in plasma [Na+] exceeding expected changes. When using AM, DM1 showed the biggest discrepancy between observed and expected change in plasma [Na+] (DM1, -1.98±0.6, p=.01; HME, -0.87±0.5, p=.12; HC -0.31±0.4 mmol/L, p=.46). In all groups, the observed Na+ and K+ excretion were significantly lower compared to the expected excretion, but no differences between groups were observed. Blood pressure was not affected by infusion.

Conclusion

DM1 patients have reduced ability for non-osmotic sodium storage, possibly due to a reduced amount of GAGs. HME patients do not show a reduced ability for non-osmotic sodium storage, perhaps by compensatory synthesis GAGs other than heparan sulfate.