Follicle-stimulating hormone stimulates circulating gonadotropin surge-attenuating/inhibiting factor bioactivity in cows

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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.

Original languageEnglish
Pages (from-to)278-285
Number of pages8
JournalBiology of Reproduction
Issue number2
Publication statusPublished - Aug 1997


  • equine chorionic-gonadotropin
  • human menopausal gonadotropin
  • luteinizing-hormone
  • superovulated women
  • factor GNSAF
  • ovarian hyperstimulation
  • preovulatory follicles
  • invitro fertilization
  • plasma-concentrations
  • pituitary-response


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