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Article

pH-Dependent Protein Binding Properties of Uremic Toxins In Vitro

1
Division of Clinical Nephrology and Rheumatology, Niigata University Graduate School of Medical and Dental Sciences, Niigata 951-8510, Japan
2
Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan
*
Author to whom correspondence should be addressed.
Received: 18 December 2020 / Revised: 30 January 2021 / Accepted: 1 February 2021 / Published: 4 February 2021
(This article belongs to the Special Issue New Strategies for the Reduction of Uremic Toxins)
Protein-bound uremic toxins (PBUTs) are difficult to remove using conventional dialysis treatment owing to their high protein-binding affinity. As pH changes the conformation of proteins, it may be associated with the binding of uremic toxins. Albumin conformation at pH 2 to 13 was analyzed using circular dichroism. The protein binding behavior between indoxyl sulfate (IS) and albumin was examined using isothermal titration calorimetry. Albumin with IS, and serum with IS, p-cresyl sulfate, indole acetic acid or phenyl sulfate, as well as serum from hemodialysis patients, were adjusted pH of 3 to 11, and the concentration of the free PBUTs was measured using mass spectrometry. Albumin was unfolded at pH < 4 or >12, and weakened interaction with IS occurred at pH < 5 or >10. The concentration of free IS in the albumin solution was increased at pH 4.0 and pH 11.0. Addition of human serum to each toxin resulted in increased free forms at acidic and alkaline pH. The pH values of serums from patients undergoing hemodialysis adjusted to 3.4 and 11.3 resulted in increased concentrations of the free forms of PBUTs. In conclusion, acidic and alkaline pH conditions changed the albumin conformation and weakened the protein binding property of PBUTs in vitro. View Full-Text
Keywords: pH; uremic toxins; albumin; indoxyl sulfate; isothermal titration calorimetry pH; uremic toxins; albumin; indoxyl sulfate; isothermal titration calorimetry
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MDPI and ACS Style

Yamamoto, S.; Sasahara, K.; Domon, M.; Yamaguchi, K.; Ito, T.; Goto, S.; Goto, Y.; Narita, I. pH-Dependent Protein Binding Properties of Uremic Toxins In Vitro. Toxins 2021, 13, 116. https://0-doi-org.brum.beds.ac.uk/10.3390/toxins13020116

AMA Style

Yamamoto S, Sasahara K, Domon M, Yamaguchi K, Ito T, Goto S, Goto Y, Narita I. pH-Dependent Protein Binding Properties of Uremic Toxins In Vitro. Toxins. 2021; 13(2):116. https://0-doi-org.brum.beds.ac.uk/10.3390/toxins13020116

Chicago/Turabian Style

Yamamoto, Suguru, Kenichi Sasahara, Mio Domon, Keiichi Yamaguchi, Toru Ito, Shin Goto, Yuji Goto, and Ichiei Narita. 2021. "pH-Dependent Protein Binding Properties of Uremic Toxins In Vitro" Toxins 13, no. 2: 116. https://0-doi-org.brum.beds.ac.uk/10.3390/toxins13020116

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