Abstract
Secretoneurin (SN) is a 33–34 amino acid neuropeptide derived from secretogranin-II (SgII), a member of the chromogranin family. GnRH increases anterior pituitary SgII messenger RNA levels concomitant with luteinizing hormone (LH) release in goldfish (gf). Synthetic gfSN stimulates LH release in vivo. Our previous study demonstrated for the first time that gfSN had a direct effect to increase LH release and production in vitro, using static incubation of goldfish pituitary tissues. Recent experiments of primary dispersed gf pituitary cell culture also showed that 1 nM and 10 nM of gfSN respectively induced 2.5-fold (p<0.001) and 1.9-fold (p<0.01) increments of LH secretion after 12 hours. Using a western blot analysis with an anti-gfSN antiserum, two SgIIderived proteins (~57 kDa and ~30 kDa) were detected in the gf pituitary, as well as one ~20-kDa protein in the gf brain. In order to detect SgII processing to generate free gfSN (3.66 kDa), we utilized a reversed-phase high-performance liquid chromatography to separate and isolate low molecular weight proteins contained in gf brain and pituitary. Mass spectrum and dot blot analyses were established for characterizing SNrelated peptides. We have potentially identified free gfSN in the brain and pituitary. Salmon GnRH (sGnRH) decreased the levels of the major SgIIderived protein (~57 kDa), by 76% (p<0.05) after 12-hour static treatment of dispersed gf pituitary cells, suggesting GnRH stimulates the generation free gfSN peptide from SgII. Immunohistochemistry revealed that SNreactive peptides are produced only in prolactin cells of the anterior pituitary. SN is found in the pituitary and hypothalamus, and is a potential new hormone or paracrine factor regulating reproductive hormone secretion. Supported by NSERC-Canada and the University of Ottawa. (platform)
Published Version
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