Somatostatin inhibits basal and growth hormone-stimulated hepatic insulin-like growth factor-I production

Nicole M. Very, Jeffrey D. Kittilson, Sarah E. Klein, Mark A. Sheridan

Research output: Contribution to journalArticle

27 Scopus citations

Abstract

Growth of vertebrates is controlled by the growth hormone (GH)-insulin-like growth factor-I (IGF-I) system, and somatostatins (SSs) have been shown to inhibit growth by reducing the release of growth hormone (GH) from the pituitary. In this study, we used rainbow trout to assess the effects of SSs on the production of IGF-I. Somatostatin-14 (SS-14-I) implantation for 15 days significantly reduced steady-state levels of IGF-I mRNA in liver and lowered IGF-I concentration in plasma compared to control animals. The direct effects of SSs were examined on hepatocytes incubated in vitro. SS-14-I inhibited basal and GH-stimulated IGF-I mRNA expression. SS-14-I inhibition of GH-stimulated IGF-I expression was concentration- and time-dependent; the ED50 was ca. 40 ng/ml and the maximum response was observed after 6 h. All SS isofoms tested, including the N-terminally extended form of SS-14-I, SS-28-I, and the [Tyr7, Gly10]-substituted forms of SS, SS-14-II, SS-25-II and SS-28-II, inhibited GH-stimulated IGF-I mRNA expression. The inhibitory effects of SS-14-I on steady-state levels of IGF-I mRNA resulted from reduced IGF-I mRNA transcription and not from altered mRNA stability. SS-14-I also reduced basal and GH-stimulated release of IGF-I into culture medium. These results indicate that SSs regulate growth in an extrapituitary manner by reducing hepatic IGF-I biosynthesis and secretion.

Original languageEnglish
Pages (from-to)19-26
Number of pages8
JournalMolecular and Cellular Endocrinology
Volume281
Issue number1-2
DOIs
StatePublished - Jan 16 2008

Keywords

  • Growth
  • IGF-I expression
  • Rainbow trout

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