IRON-TRANSFERRIN BINDING TO ISOLATED GUINEA-PIG ENTEROCYTES AND THE REGIONAL LOCALIZATION OF INTESTINAL IRON TRANSFER DURING ONTOGENY

Neonatal animals are iron replete but in comparison with adults they display increased intestinal iron absorption. In order to examine possible mechanisms for this developmental adaptation we have measured the appearance of iron in peripheral blood following 30 min exposure of duodenal and ileal segments of adult and neonatal guinea pigs in vivo to Fe-59-ascorbate. Parallel experiments have determined the kinetics of I-125-labelled diferric transferrin binding to villus enterocytes isolated from duodenum and ileum. In adult animals the rate of appearance of Fe-59 in peripheral blood was 11-fold greater following duodenal, compared to ileal exposure to the radioligand. No such regional difference was detected in the neonate. Isolated cells showed saturable binding of [I-125]transferrin which was maximal between 30 and 60 min. The kinetics of specific transferrin binding by adult duodenal and ileal enterocytes were similar and were also not significantly different to respective values in neonatal duodenal and ileal cells. Thus, it is likely that increased iron absorption in the neonate is due in part to enhanced ileal iron transfer. The interaction of transferrin with its receptor, however, is not involved in this developmental change in uptake.