title: Rat intestinal and hepatic ferritin subunit expression during development and after dietary iron feeding.
abstract: Ferritin consists of 24 heavy (H) and light (L) subunits in varying proportions in different tissues and plays a significant role in iron metabolism. We studied rat ferritin subunit expression in the duodenum and liver during early life, when a cycle of iron depletion and repletion occurs. In both tissues, ferritin contents decreased to low levels from day 3 to day 12. The ferritin on day 3 had an H/L mRNA ration of 0.9 and an H/L subunit ratio of 0.6. The decrease of tissue ferritin levels, but not mRNA, on day 12 suggests translational repression consistent with iron depletion. In the duodenum, a twofold increase in both H and mRNA and subunit protein occurred on day 18. The subsequent increase of H mRNA was accompanied by a 50% decrease in L mRNA, resulting in the increase of H/L mRNA and subunit ratios to 7.9 and 9, respectively, by day 32. In contrast, liver H/L mRNA and subunit ratios were similar throughout development. The possibility that dietary iron regulates duodenal ferritin subunit expression was investigated. When day 12 rats were fed 6 ml of a milk formula containing 56 microgram/ml iron for 18 h, dietary iron increased the duodenal levels of L mRNA but not H mRNA. In contrast, hepatic H and L mRNA levels did not change. Dietary iron promoted greater increases in ferritin protein than mRNA in both tissues. Thus a shift from L-rich to H-rich ferritin isoforms occurs in the duodenum but not in the liver during neonatal development. This change is regulated at the pretranslational level and is independent of dietary iron.
authors.affiliation: Department of Medicine, Louisiana State University Medical Center, Shreveport, 71130-3932, USA.
authors.forename: K Y
authors.initials: KY
authors.lastname: Yeh
authors.forename: X
authors.initials: X
authors.lastname: Alvarez-Hernandez
authors.forename: J
authors.initials: J
authors.lastname: Glass
authors.forename: M
authors.initials: M
authors.lastname: Yeh
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D015152:Blotting, Northern; D004032:Diet; D004386:Duodenum / Q000254:growth & development / Q000378:metabolism*; D005260:Female; D005293:Ferritins / Q000096:biosynthesis* / Q000737:chemistry; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D007408:Intestinal Absorption; D007501:Iron / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology*; D008099:Liver / Q000254:growth & development / Q000378:metabolism*; D046911:Macromolecular Substances; D008297:Male; D009928:Organ Specificity; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D046911:Macromolecular Substances; D005293:Ferritins; D007501:Iron