Follicle-stimulating hormone stimulates circulating gonadotropin surge-attenuating/inhibiting factor bioactivity in cows.
This study aimed to determine whether superovulation in cattle stimulates gonadotropin surge-attenuating/inhibiting factor (GnSAF/IF) bioactivity, as it does in humans. Blood samples were collected from cows (n = 7 per treatment) at -4, 8, 20, 32, 44, 56, and 68 h after injections of saline, eCG, or FSH. Equal volumes of plasma at each treatment and time point were pooled, and GnSAF/IF and inhibin bioactivities were measured using an established rat pituitary cell culture bioassay. Plasma from saline- and eCG-treated cows had little effect on GnRH-induced LH secretion (116.3 +/- 8.3%-81.6 +/- 6.0% of control), while plasma from FSH-treated cows produced a time-dependent suppression of GnRH-induced LH secretion, falling to 64.6 +/- 4.0% of the control value at 56 h after first FSH injection (p < 0.001). The GnSAF/IF bioactivity from the 56-h plasma eluted at pH 5.73 by pseudochromatofocusing-similar to the GnSAF/IF isoelectric point value of 5.81 determined using serum from superovulated women. Plasma from FSH-treated cows reduced basal FSH secretion more than plasma from eCG-treated cows (to 55.5 +/- 5.7% and 63.2 +/- 6.6% of the control value, respectively, p < 0.01) although immunoreactive inhibin concentrations were similar between the two groups. We conclude that FSH, but not eCG, treatment causes a time-dependent production of circulating GnSAF/IF bioactivity in cattle.
Fowler
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PA
Department of Obstetrics & Gynaecology, University of Aberdeen, Scotland, United Kingdom. p.a.fowler@abdn.ac.uk
Price
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CA
D000818:Animals; D001681:Biological Assay; D002417:Cattle; D002478:Cells, Cultured; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology*; D042341:Gonadal Hormones; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D006801:Humans; D007265:Inhibins / Q000097:blood; D007986:Luteinizing Hormone / Q000378:metabolism; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism; D011506:Proteins / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013480:Superovulation
D006063:Chorionic Gonadotropin; D042341:Gonadal Hormones; D011506:Proteins; C080538:attenuin; D007987:Gonadotropin-Releasing Hormone; D007265:Inhibins; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone