Iron absorptive function of neonatal pig intestine.

To define the iron absorptive phase across the intestinal mucosa of neonatal pigs, the final SgFe concentration ratio of serosal to mucosal medium of everted gut sac at 1 hr incubation was measured. With .2 btg carrier iron (ferric citrate with molecular weight of 1,500) per milliliter of both the serosal and mucosal medium, the duodenum transported the iron against the concentration gradient from the mucosa to the serosa, wtaereas SgFe concentration ratio of the serosal to mucosal medium of the jejunum and ileum decreased from the initial value 1.0 to less than 1.0. With 100 #g iron per milliliter of the respective medium, however, SgFe concentration gradients of the serosal to mucosal medium of all portions of the intestine were reduced to less than 1.0. When iron concentration of the serosal medium was zero, SgFe concentration ratio of the serosal to mucosal medium under .2/~g iron per milliliter of the mucosal incubation fluid was much higher in the duodenum and jejunum than in the ileum from birth to 7 days of age. With 100 /ag iron per milliliter of the mucosal medium, however, the iron transfer from the mucosal to the serosal medium decreased markedly in the duodenum and jejunum. Accordingly, SgFe concentration ratio of serosal to mucosal medium was similar in all segments of the small intestine under the increased dose. Also, the elevated dose of 300 ~tg carrier iron per centimeter of t ied-off small intestine eliminated regional variations of