Effect of natural GnRH variants on gonadotropin secretion in two rat anterior pituitary cell models.

LUX-LANTOS VA; MONGIAT LA; BIANCHI MS; MONTANER AD; SOMOZA GM; LIBERTUN C

Sidney, Australia

Congreso; 11th International Congress of Endocrinology.; 2000

Gonadotropin-releasing-hormone (GnRH) regulates reproduction physiology. Several isoforms of GnRH have been described in different species. More than one variant are expressed in the brain of different vertebrates. We compare the potency of five natural variants: mammalian (mGnRH), guinea-pig (gpGnRH), chickenII (cGnRH-II), lampreyIII (lGnRH-III) and salmon (sGnRH), on two rat anterior pituitary cell models: adult males (M) and 15 day-old females (F). Cells were cultured 4d and incubated 1h in serum-free medium containing the variants (1.10-11 to 1.10-7M). LH and FSH were analyzed by RIA. In F, at 1.10-7M, mGnRH increased LH release 2,9 and FSH 2,7 times (p<0,01). cGnRH-II augmented LH 2,6 times (p<0,01) and did not modify FSH. LH was also stimulated at 1.10-9M by mGnRH and cGnRH-II, and FSH by mGnRH at 1.10-11 and 1.10-9M. Only at 1.10-7M, gpGnRH and sGnRH increased LH by 1,81 and 2,12 (p<0,01) respectively, and FSH by 1,96 and 1,97 (p<0,05) respectively. lGnRH-III was devoid of effect. In M mGnRH and cGnRH-II released LH and FSH only at 1.10-7M. gpGnRH and lGnRH-III  had no effect. We show that mGnRH is the most potent variant, followed by cGnRH-II. This is the first time that the biologic activity of gpGnRH has been demonstrated. lGnRh-III did not modify gonadotropin levels. Supported by CONICET, UBA,  ANPCYT.