Rat intestinal and hepatic ferritin subunit expression during
development and after dietary iron feeding.
Yeh, Kwo-Yih, Xavier Alvarez-Hernandez, Jonathan Glass, and Mary Yeh.
Sections of Gastroenterology and Hematology/Oncology, Department of
Medicine and Center for Excellence in Cancer Research, Treatment and
Education, Louisiana State University Medical Center, Shreveport,
LA
APStracts 2:0179G, 1995.
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 the 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 ratio of 0.9 and 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 two-fold increase in both H mRNA and subunit protein had
occurred on day 18. The subsequent increase of H 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 [mu]g/ml iron for 18 h,
dietary iron increased the duodenal L but not H mRNA levels. 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.
Received 6 October 1994; accepted in final form 28 August 1995.
APS Manuscript Number G404-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.