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 [Glu¹, Tyr⁷, Gly¹⁰] SRIH-14 at its C-terminus, and PSS-III encodes [Pro²] 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.

Profiling neuroendocrine gene expression changes following fadrozole-induced estrogen decline in the female goldfish

“…We identified numerous candidate estrogen-responsive genes and confirmed the expression change of calmodulin, activin-␤A, and ODC1 by real-time PCR. Some other genes, for example MMP9 (31) and preprosomatostatin-14 (13), have also been shown to be E2-regulated in the goldfish brain. We also identified additional genes whose homologs are subjected to E2 regulation in other species.…”

Prolactin-releasing peptide, food intake, and hydromineral balance in goldfish

“…Total RNA used for each tissue was selected so as to fall in the midrange of the curve under normal (control) conditions, giving optimal resolution for experimentally induced modulation of transcript abundance (for details, see Ref. 5). For pituitary PRL mRNA analysis, a partial fragment (ϳ700 bp) of [␣Ϫ 32 P]dCTP-labeled goldfish PRL cDNA (GenBank accession no.…”

Periprandial changes in growth hormone release in goldfish: role of somatostatin, ghrelin, and gastrin-releasing peptide

“…Goldfish ghrelin (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) with an octanoyl modification in the Ser 3 residue was synthesized in the laboratory of Dr. Jean E. Rivier (Clayton Foundation Laboratories for Peptide Biology, The Salk Institute of Biological Sciences, San Diego, CA). Stock solutions were made in fish physiological saline (0.65% NaCl) or Milli-Q water, aliquoted, and stored at Ϫ20°C.…”

“…The labeled probes were purified through a silica cartridge using the QIAquick nucleotide removal kit (Qiagen, Santa Clarita, CA). The specificity of the probes and the quantitative relationship between amount of total RNA and the measured signal were previously demonstrated (10,73). Hybridization was performed as previously described (10).…”

“…The specificity of the probes and the quantitative relationship between amount of total RNA and the measured signal were previously demonstrated (10,73). Hybridization was performed as previously described (10). Briefly, the membranes were prehybridized in hybridization solution (0.5 M Na 2HPO4, 7% SDS, 1 mM EDTA, 1% BSA) for 3 h. The hybridization solution was then replaced with fresh hybridization solution, and 10 6 counts ⅐ min Ϫ1 ⅐ ml Ϫ1 of labeled probe were added.…”