Mechanisms of absorption of caseinophosphopeptide bound iron

Binding iron (Fe) to the 1-25 caseinophosphopeptide obtained from enzyme hy drolysis of beta casein (beta CPP) improves Fe bioavailability in the rat. To assess the mechanisms involved in its absorption, a perfused, vasculariz ed duodenal rat loop model was used in controls and in Fe-deficient (bleedi ng of 25% blood volume) rats. Inhibitors of oxidative phosphorylation [2-4 dinitrophenol (DNP)] and/or of endocytosis [phenylarsine oxide (PAO)] were added to the perfusion solution containing 50 mu M Fe as beta CPP bound Fe (Fe-beta CPP) or gluconate (Fe Gluc). Fe-beta CPP enhanced Fe uptake, reduc ed mucosal storage, and improved net absorption both in controls and in def icient animals. DNP reduced uptake, mucosal storage, and net absorption by the same percentage in Fe-beta CPP and Fe Glue perfused rats in both contro l and Fe-deficient animals. PAO decreased uptake, mucosal storage, and net absorption of Fe-beta CPP but not of Fe Glue. At the end of the experiment Fe serum levels were increased only in Fe Glue animals. These results confi rm the improved bioavailability of beta CPP bound Fe. They suggest that at least part of its absorption can occur by a different pathway than usual Fe salts. Fe-beta CPP can be taken up by endocytosis and absorbed bound to am ino acids or peptides. (C) Elsevier Science Inc, 1999, All rights reserved.