The secretogranin II-derived peptide secretoneurin stimulates luteinizing hormone secretion from gonadotrophs.

ZHAO E; BASAK A; WONG AOL; KO W; CHEN A; LÓPEZ GC; GREY CL; CANOSA LF; SOMOZA GM; CHANG JP; TRUDEAU VL

ENDOCRINOLOGY

ENDOCRINE SOC

Año: 2009 vol. 150 p. 2273 - 2282

0013-7227

Secretoneurin (SN) is a 33- to 34-amino acid neuropeptide derived from secretogranin-II, a memberof the chromogranin family. We previously synthesized a putative goldfish (gf) SN and demonstratedits ability to stimulate LH release in vivo. However, it was not known whether goldfishactually produced the free SN peptide or whether SN directly stimulates LH release from isolatedpituitary cells. Using a combination of reverse-phase HPLC and mass spectrometry analysis, weisolated for the first time a 34-amino acid free gfSN peptide from the whole brain. Moreover,Western blot analysis indicated the existence of this peptide in goldfish pituitary. Immunocytochemicallocalization studies revealed the presence of SN immunoreactivity in prolactin cells ofrostral pars distalis of the anterior pituitary. Additionally, we found that magnocellular cells of thegoldfish preoptic region are highly immunoreactive for SN. These neurons send heavily labeledprojections that pass through the pituitary stalk and innervate the neurointermediate and anteriorlobes. In static 12-h incubation of dispersed pituitary cells, application of SN antiserum reduced LHlevels, whereas 1 and 10 nM gfSN, respectively, induced 2.5-fold (P
0.001) and 1.9-fold (P
0.01)increments of LH release into the medium, increases similar to those elicited by 100 nM concentrationsof GnRH. Like GnRH, gfSN elevated intracellular Ca2in identified gonadotrophs. Whereaswedo not yet know the relative contribution of neural SN or pituitary SN to LH release,weproposethat SN could act as a neuroendocrine and/or paracrine factor to regulate LH release from theanterior pituitary.