Effect of FSH infusion on follicle development in GnRH agonist-treated gilts.
The aim was to investigate the effect of infusion of purified FSH alone on follicle development in hypogonadotrophic GnRH agonist-treated gilts. Large-White hybrid gilts (n = 12) were treated during the mid-luteal phase and again after 28 days (day 0) with a potent slow releasing GnRH agonist. On day 3, seven gilts were infused for 168 h with 1.5 S1 units oFSH h-1 (equivalent to 1.5 units of bioactivity of NIH-FSH-S1 standard) and blood samples were collected. Ovaries were then recovered and all follicles > or = 1 mm in diameter were dissected and incubated for 2 h in 1 ml Eagle's minimum essential medium. The ovaries were recovered from the remaining five GnRH agonist-treated gilts on day 10 and also from five cyclic gilts during the late follicular phase (controls). Plasma FSH concentrations in GnRH agonist-treated gilts were lower (P < 0.01) than in follicular phase controls, increased (P < 0.001) after 1 h of FSH infusion and reached a plateau similar (P > 0.1) to that of controls after 8 h. Basal LH concentrations were similar (P > 0.1) between GnRH agonist-treated and control gilts and remained unchanged (P > 0.1) throughout the infusion period. GnRH agonist treatment reduced (P < 0.01) basal oestradiol concentrations compared with control gilts. Infusion with FSH alone increased (P < 0.001) plasma oestradiol concentrations after 96 h compared with those before infusion; when the animals were killed oestradiol concentrations were higher (P < 0.01) in GnRH agonist-treated gilts infused with FSH than in controls. This was also apparent by vulval swelling and behavioural oestrus. There were more follicles > or 1 mm in diameter in the GnRH agonist-treated groups than in the controls (184, 153 and 86 per animal; P < 0.01). Infusion with FSH increased the maximum follicle diameter (GnRH agonist: < 4 mm; FSH infused: < 12 mm; controls: < 10 mm) and tended to increase (P < 0.07) the mean number of follicles > or = 6 mm diameter per animal (FSH infused: 53; controls: 21). Total oestradiol production in vitro by follicles > or = 1 mm was higher (P < 0.01) in GnRH agonist-treated gilts infused with FSH and in follicular phase controls than in animals treated with GnRH agonist alone. However, oestradiol and testosterone secretion in vitro per follicle > or = 6 mm in diameter was lower (P < 0.05) in FSH-infused animals than in controls. In summary, although infusion of FSH alone stimulated the growth of multiple follicles of preovulatory size in GnRH agonist-treated gilts, steroidogenic output by individual follicles was impaired.
Picton
H M
HM
Division of Animal Physiology, School of Biological Sciences, University of Nottingham, Loughborough, UK.
Miller
A T
AT
Hunter
M G
MG
D000704:Analysis of Variance; D000818:Animals; D046508:Culture Techniques; D004958:Estradiol / Q000097:blood / Q000378:metabolism; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood / Q000494:pharmacology*; D005498:Follicular Phase; D012739:Gonadal Steroid Hormones / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000097:blood; D008186:Luteolytic Agents / Q000494:pharmacology*; D006080:Ovarian Follicle / Q000187:drug effects* / Q000378:metabolism; D010053:Ovary / Q000187:drug effects; D011897:Random Allocation; D013552:Swine; D013739:Testosterone / Q000378:metabolism; D017329:Triptorelin Pamoate / Q000494:pharmacology*; D014599:Uterus / Q000187:drug effects
D012739:Gonadal Steroid Hormones; D008186:Luteolytic Agents; D017329:Triptorelin Pamoate; D013739:Testosterone; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone