Effects of gonadotrophin surge-attenuating factor on the two pools of gonadotrophin-releasing hormone-induced luteinizing hormone secretion in vitro.
In order to study the in-vitro mechanism of action of gonadotrophin surge-attenuating factor (GnSAF), ovine pituitary monolayers were incubated for 48 h either with steroid-free follicular fluid from women in whom ovulation had been induced or oestradiol or progesterone. Monolayers were also incubated with 10-30 and > 30 kDa follicular fluid fractions. The effect of these preparations on gonadotrophin-releasing hormone (GnRH)-induced luteinizing hormone (LH) secretion was then determined by incubation with GnRH for between 15 and 240 min. Incubation with steroid-free follicular fluid resulted in the significant attenuation of both the acutely releasable LH pool (LH 54.3 +/- 3.0% of control secretion at 15 min of GnRH incubation) and the reserve LH pool (LH 36.8 +/- 1.6% of control secretion at 240 min GnRH incubation). The 10-30 kDa follicular fluid fraction had similar effects while the > 30 kDa follicular fluid fraction significantly stimulated GnRH-induced LH secretion, with concentrations up to 134.0 +/- 8.6% of controls. Oestradiol or progesterone at doses of 1000 nmol/l/well did not significantly reduce any aspect of GnRH-induced LH secretion (never < 95.1 +/- 15.1% of controls). These results demonstrate that GnSAF markedly attenuates both the acutely releasable and reserve pools of GnRH-induced LH secretion. Inhibin, oestradiol and progesterone are not responsible for the marked attenuation of either the initial or reserve pools of GnRH-induced LH secretion.
Fowler
P A
PA
Department of Obstetrics and Gynaecology, University of Aberdeen, Foresterhill, UK.
Messinis
I E
IE
Cunningham
P
P
Fraser
M
M
Templeton
A A
AA
D000818:Animals; D001481:Basal Metabolism; D001790:Blood Physiological Phenomena; D002478:Cells, Cultured; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D015571:Follicular Fluid / Q000502:physiology; D042341:Gonadal Hormones; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology*; D006801:Humans; D007265:Inhibins / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000378:metabolism*; D008297:Male; D008970:Molecular Weight; D010062:Ovulation Induction / Q000379:methods; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism; D011374:Progesterone / Q000494:pharmacology; D011506:Proteins; D012756:Sheep
D042341:Gonadal Hormones; D011506:Proteins; C080538:attenuin; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D004958:Estradiol; D007265:Inhibins; D007986:Luteinizing Hormone