title: Iron-responsive element-binding protein in hemochromatosis liver and intestine.
abstract: Iron-responsive element-binding protein (IRE-BP) activity was studied in liver and intestinal samples of hemochromatosis and control patients using a short 32P-IRE-RNA probe on "retardation" nondenaturing polyacrylamide gels. IRE-BP activity was assessed in liver biopsy specimens in 36 patients--16 hemochromatosis homozygotes, 4 hemochromatosis heterozygotes, 6 patients with secondary iron overload, and 10 control patients with normal hepatic iron concentrations. Intestinal IRE-BP activity was assessed in 14 hemochromatosis homozygotes and 16 normal subjects. Endogenous IRE-BP activity was determined from 32P retarded on the gel, and total IRE-BP activity was assessed after reducing tissue samples with 2-mercaptoethanol. Hepatic endogenous IRE-BP activity was inversely related to hepatic iron concentration (r = .59, P < .0002). Mean hepatic endogenous IRE-BP activity in the hemochromatosis homozygotes, 0.25 +/- 0.04 pmol/mg protein, was significantly decreased compared with values in the normal controls, 0.45 +/- 0.06 pmol/mg protein, P < .05. Hepatic total IRE-BP was also significantly decreased in the hemochromatosis patients by gel retardation assay and Western blotting with anti-IRE-BP antibody. Intestinal endogenous IRE-BP activity, total IRE-BP activity, and iron concentration did not significantly differ between hemochromatosis patients and normal control subjects. This suggests that both endogenous IRE-BP activity and the total amount of the protein are downregulated in the liver by tissue iron. Intestinal IRE-BP activity that regulates intestinal transferrin receptor expression is normal in hemochromatosis and appropriate for the intracellular iron concentration.
authors.affiliation: Department of Medicine, University Hospital, University of Western Ontario, London, Canada.
authors.forename: P R
authors.initials: PR
authors.lastname: Flanagan
authors.forename: A
authors.initials: A
authors.lastname: Hajdu
authors.forename: P C
authors.initials: PC
authors.lastname: Adams
mesh_terms: D000328:Adult; D000368:Aged; D015153:Blotting, Western; D005260:Female; D006432:Hemochromatosis / Q000378:metabolism*; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D035925:Iron-Regulatory Proteins; D008099:Liver / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D016601:RNA-Binding Proteins / Q000378:metabolism*; D011990:Receptors, Transferrin / Q000378:metabolism; D012016:Reference Values
chemical_list: D035925:Iron-Regulatory Proteins; D016601:RNA-Binding Proteins; D011990:Receptors, Transferrin