Meeting Abstract

95.1  Saturday, Jan. 7  Environmental Estrogens Inhibit the Expression of Insulin-like Growth Factors 1 and 2 in the Liver and Gill of Rainbow Trout in vitro. HANSON,, A.M.*; SHERIDAN,, M.A.; North Dakota St. Univ.

The increasing production, use, and disposal of an expanding array of chemicals that enter the environment pose a serious threat to terrestrial and aquatic animals, as well as to humans. Fish in aquatic habitats are exposed to an increasing array and concentration of environmental contaminants, including environmental estrogens (EE). Previously, we observed that in vivo exposure of juvenile rainbow trout (ca. 50 g) to varying concentrations of 17β-estradiol (E2), β-sitosterol (βS), and 4-n-nonylphenol (NP) for 28 days (14 C; 12L:12D) depressed growth and altered the expression of various elements of the growth hormone (GH)-insulin-like growth factor (IGF) system. In this study, we assessed the direct effects of EE on GH sensitivity as assessed by mRNA expression of GH receptors (GHR) and on IGF production as assessed by expression of IGF-1 and IGF-2 mRNAs in selected tissues. None of the EE tested affected the expression of GHRs in either liver or gill. By contrast, E2, βS and NP inhibited the expression of both IGF-1 and IGF-2 in a time- and concentration-related manner in liver. Although the response evoked by all of the EE was similar for hepatic IGF-1 and IGF-2 mRNA expression, the potency and efficacy varied with EE; the rank order of potency/efficacy was as follows: E2=NP> βS. E2, βS and NP also inhibited the expression of IGF-1 and IGF-2 mRNAs in a time- and concentration-related manner in gill; patterns for efficacy and potency similar to those in liver also were observed in gill. These findings indicate that selected EE can directly influence the growth of post-embryonic rainbow trout by inhibiting the synthesis of IGFs (Supported by NSF IOS 0920116 to MAS).