Adsorption of Dietary Phosphate in Gut with Anion Exchange Resin

Hiroyoshi INOUE

Radioisotope Institute for Basic and Clinical Medicine, Kurume University School of Medicine; 67 Asahi-machi, Kurume-shi 830-0011 Japan

In order to study the characteristics of anion exchange resin that may effectively bound the dietary phosphate in digestive system, in vitro and in vivo studies in phosphate binding were carried out by comparing anion exchange resins, PAA-B, WA 10, and Dowex 1×8, with calcium carbonate. In vitro phosphate binding experiments, the anion exchange resins used bound lesser phosphate than calcium carbonate at pH 7. The binding equilibrium of resins, however, was reached within 1 hour and was more rapidly than that of calcium carbonate without pretreatment of acid solution. In vivo phosphate binding experiments, the fecal phosphorus excretions of rats with PAA-B, WA 10, Dowex 1×8, or calcium carbonate were increased by 77.4, 38.4, 8.4, or 57.7%, respectively. While the uric phosphorus excretions were decreased by 73.9, 42.7, 20.5, or 66.9%, respectively. Famotidine, histamine H2 receptor antagonist, significantly reduced phosphate binding of calcium carbonate ( P<0.01) while it had no influence on anion exchange resins. These results suggest that anion exchange resin, especially in which the primary and secondary amino type anion exchange groups are maximally introduced, has a bright prospect of an effective drug for treating hyperphosphatemia in patients with chronic renal disease of end stage and with hemodialysis.

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