| Summary: | The growth hormone (Gh)/insulin‐like growth‐factor (Igf) system is a key regulator of growth in teleost fishes, including salmonids. Igfs interact with a suite of binding proteins, termed Igf binding proteins (Igfbps), which modify their biological activities. Atlantic salmon ( Salmo salar ) express an expanded array of igfbp gene transcripts in liver, the primary site of Igfbp production. While gonadal steroids are known to impact the growth of fishes, there is little information on how androgens and estrogens affect the expression of various igfbps . In the current study, we characterized how 14‐day implants of adrenosterone (OA), testosterone (T) or 17 β ‐estradiol (E 2 ) affected the Gh/Igf/Igfbp network in Atlantic salmon smolts. OA did not affect any of the parameters studied. There were no effects of T or E 2 on body mass, plasma levels of Igf1, or hepatic igf1 , igf2 or gh receptor mRNA levels. E 2 stimulated hepatic estrogen receptor α mRNA levels by 17‐fold, while E 2 and T stimulated hepatic vitellogenin mRNA levels by 140‐ and 19‐fold, respectively. Hepatic igfbp1b1 and igfbp4 mRNA levels were diminished by E 2 but not T, whereas igfbp2a was diminished by T, but not E 2 . Alternatively, both T and E 2 stimulated igfbp5a . igfbp2b2 , igfbp5b2 and igfbp6b were not impacted by any of the tested steroids. Our findings suggest that steroid‐specific effects on the gene expression of various igfbps provide a means for gonadal steroids to modulate the Gh/Igf system. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .
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