IRON UPTAKE FROM LACTOFERRIN BY INTESTINAL BRUSH-BORDER MEMBRANE-VESICLES OF HUMAN NEONATES

It is uncertain to what extent the binding of human lactoferrin (LF) to its receptor in the intestinal brush-border membrane affects iron uptake in infants. The purpose of this study was to investigate iron uptake from human LF by brush-border membrane vesicles (BBMV) obtained from the small intestine of human neonates. LF was purified from pooled human colostrum. Uptake experiments were performed by incubation of Fe-55-citrate or Fe-55-LF with BBMV, followed by rapid filtration through microporous filters. Fe-55 uptake from LF by BBMV was dependent on pH, with a maximum at 7.5, and increased with incubation time, reaching a maximum at 1 min. When Fe-55 was bound to citrate, uptake was slower (maximum at 5 min) and not dependent on pH. In both experiments, the maximum uptake of iron bound to LF was about twice that of iron bound to citrate (230 pmol and 105 pmol/mg microvillus protein, respectively). Partial degradation of LF in two fragments resulted in the loss of its capacity to increase iron uptake by BBMV. From these preliminary results we conclude that LF may increase iron absorption during the neonatal period, contributing to the high bioavailability of this mineral in human milk.