Meeting Abstract

11.4  Thursday, Jan. 3  Growth Hormone Receptor Signal Transduction in Rainbow Trout Hepatocytes REINDL, K.M.*; SHERIDAN, M.A.; North Dakota State Univ., Fargo katie.reindl@ndsu.edu

Growth hormone (GH) initiates many of its growth-promoting actions by binding to growth hormone receptors (GHR) and stimulating the synthesis and release of insulin-like growth factor-1 (IGF-1) from the liver and other sites. While the signaling mechanisms initiated by growth hormone have been elucidated in mammals, little is known about GH transduction events in fish. The aim of this research was to determine the molecular signaling events of GH in rainbow trout, which we previously found to express two distinct GHRs. Trout hepatocytes were isolated and treated with salmon growth hormone (sGH) for 12 hours. Total RNA was isolated and reverse transcribed into cDNA and IGF-1 levels were determined by real-time PCR. Growth hormone treatment of trout hepatocytes resulted in a significant increase in IGF-1 mRNA. Further, hepatocytes were treated with sGH for various times and doses and protein extracts were collected. Western blots were performed to determine the signal transduction pathways initiated in response to growth hormone treatment. Growth hormone rapidly stimulated the Jak/STAT pathway with maximal phosphorylation of Jak2 within 10 minutes. Growth hormone also triggered the Erk1/2 and Akt pathways. These results indicate that GH signal transduction in rainbow trout is similar to that in mammals where GH activates the Jak/STAT, Erk, and Akt pathways. Future studies will be conducted to elucidate which effector pathways link to IGF-1 expression and to determine whether the distinct GHRs use the same or different effector pathways. (Supported by NSF grant IOB 0444860 to M.A.S.)