Meeting Abstract
P1.128 Monday, Jan. 4 Regulation of the Growth Hormone-Insulin-like Growth Factor System by Cortisol and Thyroxin in Rainbow Trout NORBECK, L.A.*; SHERIDAN, M.A.; North Dakota State Univ. Lindsey.Norbeck@ndsu.edu
Previously, it was shown that cortisol and thyroxine (T4) modulate the growth of teleost fish. In this study we used rainbow trout (Oncorhynchus mykiss) to examine the influence of cortisol and T4 on the growth hormone (GH)-insulin-like growth factor (IGF) system. The direct effects of cortisol and T4 were examined in liver pieces (ca. 1 mm3) and isolated gill filaments incubated in vitro. Expression of mRNAs encoding GH receptor 1 (GHR1), GHR2, IGF-1, IGF-2, IGF type 1 A receptor (IGFR1A), and IGFR1B were determined by quantitative real-time PCR. Cortisol up-regulated GH-IGF system components in a time- and concentration-related manner. In liver, cortisol increased steady-state levels of mRNAs encoding GHR1 and GHR2. Cortisol also increased hepatic expression of both IGF-1 and IGF-2 mRNAs. In gill, cortisol increased levels of GHR1 and GHR2 mRNAs as well as levels of IGFR1A and IGFR1B mRNAs. T4 also up-regulated components of the GH-IGF system in a time- and concentration-related manner. In liver, T4 increased levels of mRNAs encoding GHR1, GHR2, IGF-1, and IGF-2. In gill, T4 increased the expression of both GHR1 and GHR2 mRNAs as well as of both IGFR1A and IGFR1B mRNAs. These results indicate that cortisol and T4 affect growth by modulating the GH-IGF system at several levels, including increasing sensitivity to GH, increasing IGF production, and increasing peripheral sensitivity to IGF. (Supported by NSF IOS 0920116)
