Selection of the dominant follicle in cattle: role of two-way functional coupling between follicle-stimulating hormone and the follicles

• Published in: Biology of reproduction Vol. 62; no. 4; pp. 920 - 927
• Main Authors: Ginther, O.J, Bergfelt, D.R, Kulick, L.J, Kot, K
• Format: Journal Article
• Language: English
• Published: Madison, WI Society for the Study of Reproduction 01-04-2000
• Subjects: Animals; Biological and medical sciences; Cattle; diameter; estradiol; Estradiol - blood; estrous cycle; Female; follicle dominance; Follicle Stimulating Hormone - blood; Follicle Stimulating Hormone - metabolism; Follicle Stimulating Hormone - physiology; follicle-stimulating hormone; follicular deviation; follicular wave; Fundamental and applied biological sciences. Psychology; Graafian follicles; growth; heifers; hormonal regulation; Hormone metabolism and regulation; hormone secretion; luteinizing hormone; Luteinizing Hormone - blood; Mammalian female genital system; Ovarian Follicle - anatomy & histology; Ovarian Follicle - diagnostic imaging; Ovarian Follicle - physiology; Ultrasonography; Vertebrates: reproduction; Ovary; Vertebrata; Mammalia; Adenohypophyseal hormone; Female genital system; Ox; Dominance; Artiodactyla; Gonadotropin; Ovarian follicle; Ungulata; Follicle stimulating hormone
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod62.4.920

The functional coupling between the declining portion of the FSH surge and the growing follicles of a wave was studied by
treating heifers with a minimal dose of estradiol to decrease FSH concentrations without an associated change in LH concentrations.
Estradiol treatment when the largest follicle reached ≥ 6.0 mm (Hour 0) resulted in depression of both FSH concentrations
and diameter of the largest follicle by Hour 8. The smaller follicles were also inhibited. These results supported the hypothesis
that FSH continues to be needed by the growing follicles even when the FSH concentrations are decreasing during the declining
portion of the FSH surge. Estradiol treatment when the largest follicle was ≥ 8.5 mm (expected time of follicular deviation)
also resulted in a transient decrease in both FSH concentrations and diameter of the largest follicle, but the diameters of
the smaller follicles were not affected. These results supported the hypothesis that the low concentrations of FSH at the
expected time of deviation, although inadequate for the smaller follicles, were required for continued growth of the largest
follicle.
In another study, ablation (Hour 0) of the largest follicle was done at ≥ 7.5 mm vs. ≥ 8.5 mm. The mean FSH concentrations
for the 8.5-mm groups were greater for the ablation group than for the control group at Hours 8 and 12, but there was no difference
between the 7.5-mm groups at any hour. These results supported the hypothesis that by the time the largest follicle reaches
the expected beginning of deviation it has developed a greater capacity for suppressing FSH.
It is postulated that the essence of the selection of a dominant follicle is a close two-way functional coupling between changing
FSH concentrations and follicular growth.