Comparison of binding by concentrated peritoneal dialysate and serum
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Published on: July 21, 2015
P F Gulyassy1, T A Depner, G C Shearer
1Department of Internal Medicine, University of California, Davis.
Abstract:
Major advances in dialysis therapy have occurred over the last decade, yet various abnormalities persist in end-stage renal disease (ESRD) patients. The etiology of these residual defects remains largely unknown. We are currently testing the hypothesis that some of these abnormalities are due to retention of small molecular weight, protein bound toxins, which are poorly dialyzable. We sought an alternative to blood as a source of bound toxins. Spent peritoneal dialysate (PD) was tested as a source. With use of a series of filtration devices, PD albumin content was increased about 35-fold. Evidence of bound ligands was shown by two methods. Salicylate binding by patients' sera and concentrated PD (n = 8) were markedly reduced, unbound salicylate being 14.9 +/- 5.1% (SD) and 15.8 +/- 4.9% at albumin concentrations of 3.30 +/- 1.04 and 3.23 +/- 0.84 g/dl. Serum from eight normal subjects, diluted to 2.95 g/dl albumin, had 7.4 +/- 1.1% unbound salicylate. HPLC analysis of deproteinized concentrated dialysate was compared to ultrafiltrates of the same fluid. Numerous bound peaks were seen, particularly in the late eluting peaks. Spent PD is a rich source of protein bound ligands for further study.
Insights
Dialysis patients often have persistent abnormalities due to retained toxins. Researchers found that spent peritoneal dialysate is a rich source of these protein-bound toxins, suggesting a new avenue for studying end-stage renal disease defects.
Area of Science:
- Nephrology
- Biochemistry
Background:
- Despite advances in dialysis, end-stage renal disease (ESRD) patients exhibit persistent abnormalities.
- The underlying causes of these residual defects are not fully understood.
- Protein-bound toxins, poorly removed by dialysis, are hypothesized to contribute to these abnormalities.
Purpose of the Study:
- To investigate the hypothesis that retained small molecular weight, protein-bound toxins cause persistent abnormalities in ESRD patients.
- To identify spent peritoneal dialysate (PD) as an alternative source for studying these toxins, avoiding the need for blood samples.
Main Methods:
- Spent PD was concentrated using filtration devices to increase albumin content.
- Salicylate binding assays were performed on concentrated PD and patient sera to assess toxin binding.
- High-Performance Liquid Chromatography (HPLC) was used to analyze deproteinized dialysate and ultrafiltrates for bound ligands.
Main Results:
- Concentrated PD showed reduced salicylate binding capacity, similar to patient sera, indicating the presence of bound ligands.
- HPLC analysis revealed numerous bound peaks in concentrated dialysate, particularly in late-eluting fractions.
- Normal serum, diluted to comparable albumin levels, demonstrated significantly lower unbound salicylate.
Conclusions:
- Spent peritoneal dialysate is a viable and rich source of protein-bound toxins for further investigation.
- These findings support the hypothesis that poorly dialyzable, protein-bound toxins contribute to residual defects in ESRD patients.
- Further research using spent PD can elucidate the role of these toxins in ESRD pathophysiology.
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