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Iron Absorptive Function of Neonatal Pig Intestine

National Institute of Animal Industry, 959 Aoba-cbo, Chiba-shi, Cbiba 280, Japan

³ Request for reprints should be sent to K. Furugouri.

Abstract

To define the iron absorptive phase across the intestinal mucosa of neonatal pigs, the final ⁵⁹Fe concentration ratio of serosal to mucosal medium of everted gut sac at 1 hr incubation was measured. With .2 jug 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, whereas ⁵⁹Fe 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 µg iron per milliliter of the respective medium, however, ⁵⁹Fe 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, ⁵⁹Fe concentration ratio of the serosal to mucosal medium under .2 µg 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 ng 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, ⁵⁹Fe 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 jug carrier iron per centimeter of tied-off small intestine eliminated regional variations of intestinal absorption for iron. Although jejunum of neonatal pigs did not exhibit the iron transport against concentration gradient from the mucosa to serosa under the low iron concentration of both the mucosal and serosal medium, iron absorptive function of the jejunum was high. Movement of iron across the mucosa to serosa of the everted gut sac increased in all portions of intestine with the elvated iron concentration of mucosal medium. However, net transfer of ⁵⁹Fe per gut sac from the mucosal uptake to the serosal medium was relatively lower in duodenum than in the jejunum and ileum, irrespective of the iron concentration in the mucosal medium. The data indicate that the neonatal pig intestine fully provides active and passive transport function for iron and that the serosal site as well as the surface of the mucosal epithelium regulates the iron transfer from the lumen into the body.

¹ Present address: Laboratory of Growth Physiology, Hokkaido National Agr. Exp. Sta., Sapporo 061-01, Japan.

² Department of Animal Physiology.

⁴ The authors thank Dr. Y. Yoshino, Nippon Medical School, Tokyo for his suggestion.