Capacity of the mucosal transfer system and absorption of iron after oral administration in rats.

1. The dose dependence of the iron absorption shows a saturation characteristic if iron (0.25--5 mumoles Fe/kg body weight) is administered in tied-off intestinal segments of normal and iron-deficient rats. 2. If the iron doses (2.1--570 mumoles Fe/kg body weight) are administered by stomach tube only in normal rats a similar dose dependence curve has been obtained as after administration in tied-off intestinal segments. In iron-deficient rats the shape of the dose dependence curve is changed and shows no clear-cut saturation characteristic. 3. The differences of these dose dependence curves are discussed with respect to the differences of the methodological conditions. A saturation type kinetic for absorption cannot be expected under all experimental conditions despite of the existence of a transfer system with limited capacity for the transport of iron.