title: Regulation of expression of somatostatin genes by sex steroid hormones in goldfish forebrain.
abstract: Recently, our laboratory has identified three distinct pre-pro-somatostatin (PSS) genes in goldfish brain: PSS-I encodes for somatostatin (SRIH)-14, PSS-II encodes SRIH-28, which contains [Glu(1), Tyr(7), Gly(10)] SRIH-14 at its C-terminus, and PSS-III encodes [Pro(2)] SRIH-14. In goldfish, increasing levels of the sex steroid estradiol increase the plasma levels of growth hormone (GH). However, whether sex steroids act at the level of the brain to regulate GH release is unclear. In the present study, the effects of sex steroids on the expression of the three PSS genes in goldfish forebrain were examined. The results demonstrate that treatment with estradiol significantly increases the expression of PSS-I and PSS-III genes in both male and female fish. The effects of estradiol were evident after only 2.5 days of treatment. Testosterone treatment increased the expression of PSS-I and PSS-III genes in female but not male fish, and only at the highest dose used. In addition, the effects of testosterone were evident only after treatment for 5 or 10 days and were blocked by an aromatase inhibitor, suggesting that testosterone must be converted to estradiol to exhibit the effect. Neither estradiol nor testosterone treatment had effects on the expression of the PSS-II gene. These results suggest that sex steroids can act either directly or indirectly on the brain to regulate PSS-I and PSS-III gene expression, influencing in turn the regulation of GH secretion.
authors.affiliation: Biological Sciences Department, University of Alberta, Edmonton, Alta., Canada.
authors.forename: Luis Fabián
authors.initials: LF
authors.lastname: Canosa
authors.forename: Xinwei
authors.initials: X
authors.lastname: Lin
authors.forename: Richard E
authors.initials: RE
authors.lastname: Peter
mesh_terms: D000818:Animals; D047072:Aromatase Inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D006054:Goldfish / Q000235:genetics / Q000378:metabolism*; D013006:Growth Hormone / Q000097:blood; D007700:Kinetics; D008297:Male; D016548:Prosencephalon / Q000378:metabolism*; D011498:Protein Precursors / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D012621:Seasons; D013004:Somatostatin / Q000235:genetics*; D013739:Testosterone / Q000494:pharmacology*
chemical_list: D047072:Aromatase Inhibitors; D004791:Enzyme Inhibitors; D011498:Protein Precursors; D012333:RNA, Messenger; D013739:Testosterone; D004958:Estradiol; D013004:Somatostatin; C028456:prosomatostatin; D013006:Growth Hormone