Appearance of insulin-like growth factor mRNA in the liver and pyloric ceca of a teleost in response to exogenous growth hormone

Michael J. Shamblott, Clara M. Cheng, Douglas Bolt, Thomas T. Chen

Research output: Contribution to journalArticlepeer-review

Abstract

Augmentation of vertebrate growth by growth hormone (GH) is primarily due to its regulation of insulin-like growth factor I (IGF I) and IGF II levels. To characterize the effect of GH on the levels of IGF I and IGF II mRNA in a teleost, 10 μg of bovine GH (bGH) per g of body weight was administered to juvenile rainbow trout (Oncorhynchus mykiss) through i.p. injection. The levels of IGF I and IGF II mRNA were determined simultaneously, by using RNase protection assays, in the liver, pyloric ceca, kidney, and gill at 0, 1, 3, 6, 12, 24, 48, and 72 hr after injection. In the liver, IGF I mRNA levels were significantly elevated at 6 and 12 hr (≃2-to 3-fold, P ≤ 0.01), while IGF II mRNA levels were significantly elevated at 3 and 6 hr (≃3- fold, P ≤ 0.01). In the pyloric ceca, IGF II mRNA levels were significantly elevated at 12, 24, and 48 hr (≃3-fold, P ≤ 0.01), while IGF I mRNA was below the limits of assay accuracy. GH-dependent IGF mRNA appearance was not detected in the gill and kidney. Serum bGH levels, determined by using a radioimmunoassay, were significantly elevated at 3 and 6 hr (P < 0.005). In primary hepatocyte culture, IGF I and IGF II mRNA levels increased in a bGH dose-dependent fashion, with ED50 values of ≃45 and ≃6 ng of bGH per ml, respectively. The GH-dependent appearance of IGF II mRNA in the liver and pyloric ceca suggests important roles for this peptide hormone exclusive of IGF I.

Original languageEnglish (US)
Pages (from-to)6943-6946
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Volume92
Issue number15
DOIs
StatePublished - Jul 18 1995

Keywords

  • 18S rRNA
  • RNase protection assay
  • amino acid uptake
  • bovine growth hormone
  • hepatocyte

ASJC Scopus subject areas

  • General

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