Active transport of iron by intestine: effects of oral iron and pregnancy

The active transport of iron has been studied further with everted gut sacs and loops of duodenum in the rat. The two-step absorptive mechanism appears to be one of the cellular processes which regulates iron absorption. A single dose of iron by mouth decreases both the net mucosal uptake and the net serosal transfer of iron, as studied with gut sacs in vitro. As little as 0.1 mg Fe is effective; the inhibition observed with 4.0 mg Fe persisted for approximately 17 hr. The reduction in transport appears to result, in part at least, from a direct effect of Fe on the intestine. The active transport mechanism also responds adaptively to the level of Fe in the diet. Late pregnancy increases the Fe transport, as observed with gut sacs in vitro and duodenal loops in vivo, and the effect is primarily on the serosal transfer step.