Tissue distribution and regulation of insulin-like growth factor (IGF)-binding protein-3 messenger ribonucleic acid (mRNA) in the rat: comparison with IGF-I mRNA expression.
Insulin-like growth factor-binding protein-3 (IGFBP-3) is the most abundant IGFBP in rat and human sera. The present study demonstrates the expression of the rat IGFBP-3 gene in a large number of tissues and coexpression, but not necessarily equal expression, with IGF-I mRNA. Tissues with a major abundance of IGFBP-3 were kidney, antrum of stomach, placenta, uterus, and liver. Changes in hepatic and renal levels of IGFBP-3 mRNA were analyzed after hypophysectomy (with and without GH treatment) and in the developing postnatal rat. These results were compared to changes in IGF-I mRNA levels under the same physiological conditions. Using S1 nuclease analysis, IGFBP-3 mRNA was present in the kidney and liver of 1-day-old rats and rose significantly in both organs by week 1. Thereafter, levels remained relatively constant, particularly in the liver. This is in marked contrast to the hepatic IGF-I pattern, which showed a continual rise up to 8 weeks. Hepatic IGFBP-3 gene expression was partially GH dependent, with IGFBP-3 mRNA levels falling (approximately 50%) after hypophysectomy and rising slightly after GH treatment. These changes were much less dramatic than those in IGF-I mRNA. In contrast, the renal levels of IGFBP-3 mRNA increased after hypophysectomy, (approximately 100%), but did not decrease with GH treatment. These data suggest that IGFBP-3 mRNA abundance is regulated differently in different tissues, and in at least some tissues is less sensitive to regulation than is IGF-I mRNA.
Prince Henry's Institute of Medical Research, Melbourne, Victoria, Australia.
A L
AL
Albiston
A C
AC
Herington
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics*; D005786:Gene Expression Regulation; D013006:Growth Hormone / Q000494:pharmacology; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D012333:RNA, Messenger / Q000032:analysis*; D051381:Rats; D011919:Rats, Inbred Strains; D013002:Somatomedins / Q000378:metabolism*; D014018:Tissue Distribution
D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone