CACO-2 CELL IRON UPTAKE FROM MEAT AND CASEIN DIGESTS PARALLELS IN-VIVO STUDIES - USE OF A NOVEL IN-VITRO METHOD FOR RAPID ESTIMATION OF IRON BIOAVAILABILITY

We developed a model for assessing iron bioavailability from foods whi ch combines simulated peptic and intestinal digestion with measurement of iron uptake by Caco-2 cell monolayers. Our objective was to furthe r validate this model by determining if meat enhances Caco-2 cell iron uptake relative to casein. Caco-2 cell monolayers were covered with I -lank's balanced salt solution (HBSS) buffered with HEPES, pH 7.4. An upper chamber was created over the cells by fitting the bottom of a Co star Transwell(R) insert with a 12,000-14,000 molecular weight cut-off dialysis membrane. This membrane allowed low molecular weight iron co mplexes to diffuse into the media bathing the cells and prevented dama ge to the cells from the digestive enzymes. Prior to digestion, each s ample (homogenate of beef, chicken, fish or casein) was mixed with (Fe Cl3)-Fe-59 to achieve an iron concentration of 10 mu mol/L. Following pepsin digestion (pH 2), pH was adjusted to 7.4, pancreatic enzymes an d bile extract were added to each digest, and an aliquot was then intr oduced into the upper chamber of the culture dish. During this intesti nal digestion period, Fe-59 uptake occurred from iron that dialyzed in to the Lower chamber. The Fe-59 uptake from beef, chicken and fish dig ests was 300-400% of the Fe-59 uptake from a casein digest. Our result s parallel human absorption studies indicating that meat enhances iron absorption. The results suggest that digestion products of the meat p roteins were at least partially responsible for the enhancement of iro n uptake. Overall, this study supports the usefulness of our model as a means of assessing iron bioavailability.