Intrafollicular effect of IGF1 on development of follicle dominance in mares.
The effect of an injection of a supraphysiologic dose of rhIGF1 into the second-largest ovarian follicle (F2) at the expected beginning of deviation (F1, > or =20 mm; Day 0) on development of dominance by F2 was studied in mares (n=16; controls, n=8). F1 became dominant (> or =28 mm) in 8 of 8 and 15 of 16 follicles in the controls and treated groups, respectively. The incidence of dominance (P<0.001) and ovulation (P<0.02) for F2 was greater for the IGF1 group (13 of 16 and 10 of 16) than for the controls (1 of 8 and 1 of 8). There were day effects but no group effects or group-by-day interactions for systemic FSH, LH, estradiol, or ir-inhibin during the 4 days after treatment. In another experiment, treatment of every follicle, excluding F1, when it reached > or =20mm after the expected beginning of deviation resulted in dominance by 8 of 12 follicles treated with rhIGF1 on Days 1-3 (n=8 mares). Results demonstrated that the IGF1 system plays a pivotal intrafollicular role in the deviation mechanism without altering systemic concentrations of the gonadotropins and ovarian follicular hormones.
Ginther
O J
OJ
Eutheria Foundation, Cross Plains, WI 53528, USA. ginther@svm.vetmed.wisc.edu
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D000818:Animals; D004958:Estradiol / Q000097:blood; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D006736:Horses / Q000097:blood / Q000502:physiology*; D007265:Inhibins / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007986:Luteinizing Hormone / Q000097:blood; D006080:Ovarian Follicle / Q000187:drug effects* / Q000502:physiology; D010060:Ovulation / Q000187:drug effects* / Q000502:physiology; D018709:Statistics, Nonparametric
D004958:Estradiol; D007265:Inhibins; D007334:Insulin-Like Growth Factor I; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone