Reduction of iron/zinc interactions using metal bound to the caseinophosphopeptide 1-25 of beta-casein

We used the isolated, perfused rat duodenal loop system to assess the influ ence of binding iron (Fe) to soluble 1-25 caseinophosphopeptide (beta-CN (1 -25)), produced by the hydrolysis of beta casein, against the inhibition of its absorption by Zinc (Zn). Fe (100 mu M) was perfused as Fe gluconate (F e Glue) or bound to the beta-CN (1-25) (Fe-CN), alone (controls) or in pres ence of Zn as Zn sulfate (Zn SO4) or as (Zn-CN) at Fe:Zn ratios ranging fro m 2:1 to 1:5. Zn SO4 reduced significantly disappearance from the lumen (Q1 ) and net Fe absorption (FeAbs) at Fe:Zn ratios from 1:1.5 to 1:5 (p < 0.00 1). Fe mucosal retention (Q2) did not change significantly. When Zn was pro vided as Zn-CN, Q1, Q2 and Fe Abs did not significantly differ from control group for Fe Glue. Zn SO4 and Zn-CN did not reduce significantly Q1, Q2 no r FeAbs for Fe-CN whatever ratios considered. Binding Fe to beta-CN (1-25) prevented Zn from inhibiting its absorption by Zn and could have therapeuti c applications in dietary supplementation of trace-elements. (C) 1999 Elsev ier Science Inc.