EXPRESSION OF GENES INVOLVED IN IRON-METABOLISM IN MOUSE INTESTINE

Intestinal nonheme iron levels and mRNA levels of genes implicated in iron metabolism were measured in mice with altered iron metabolism [ch ronic (4 wk) and acute (4 days) dietary iron deficiency; iron overload and hypoxia] to investigate their role in the process and regulation of intestinal iron absorption. Mucosal nonheme iron levels were decrea sed by both chronic and acute iron deficiency and increased by iron ov erload but were not affected by hypoxia. There was evidence of a gradi ent of mucosal nonheme iron along the small intestine (duodenum, jejun um > ileum). There were also regional differences in H-ferritin (duode num > ileum) and transferrin receptor (ileum > duodenum) mRNA levels. Iron overload produced a decrease in transferrin receptor (TfR) mRNA i n the duodenum, with ferritin mRNA levels unaffected in both the duode num and ileum. Chronic iron deficiency induced a twofold increase in T fR mRNA levels in both the duodenum and ileum, whereas H- and L-ferrit in mRNA levels did not change significantly. The ratio of H- to L-ferr itin mRNA decreased significantly during exposure to hypoxia; however, individual ferritin and TfR mRNA levels were not significantly altere d. Calreticulin (mobilferrin), cysteine-rich intestinal protein, and H +-adenosinetriphosphatase mRNA levels were virtually unchanged in all models. A comparison with previously published data on changes in iron absorption leads us to conclude that 1) iron absorption can be altere d independently of effects on transcripts of genes for iron-related pr oteins, and 2) it is not essential for iron absorption to be coordinat ed with regulation of mucosal iron metabolism.