ON THE KINETICS OF IRON ABSORPTION IN MICE*

Abstract

Iron absorption was studied in mice using single doses of iron labeled with Fe59. iron ab-sorption appears to be mediated by at least 2 different mechanisms which operate simultaneously: (1) a process with kinetics that suggests an enzymatic or carrier reaction in which the amount of enzyme or carrier present is the limiting factor for the maximum amount of iron absorbed by this mechanism, and (2) a process with first-order kinetics in which the concentration of absorbable iron in the gastrointestinal lumen which is presented to the absorbing surface is the limiting factor to the amount of iron absorbed by this mechanism, and the maximum amount absorbed is determined by the size of the lethal dose. Each of these 2 processes is influenced by a different degree by the state of the body iron stores, absorption being inhibited by an increase or enhanced by a decrease in body iron.