Ethylene Glycol Dimethacrylate Cross-linking Anion Exchange Resin as Phosphate Binder: Effects on Rat gut and Digestion by Small Intestine Contents

In the present study, ethylene glycol dimethacrylate cross-linking 4-vinylpyridinium anion exchange resin (EGDMA-4VP) effectively bound dietary phosphate in normal rats. However, EGDMA-4VP induced more adverse effects in rat gut than cellulose or Dowex 1X2 (both of which have higher water content), and caused damage to the intestine. In order to resolve this seeming paradox, digestion of EGDMA-4VP with rat small intestine content (S-9 fraction) and carboxyl esterase was investigated in vitro to examine the stability of the resin under conditions it would be subjected to as an orally administered medicine. EGDMA-4VP was digested by small intestinal enzymes, with the exception of carboxyl esterase, and the degradation product ethylene glycol (EG) caused reversible relaxation of longitudinal muscle (but not circular muscle) in rat small intestine. Degradation products increased uptake of 3H2O into primary cultured rat small intestinal muscle cells, but the increase was not significant.