Age-related dynamics of follicles and hormones during an induced ovulatory follicular wave in mares.
An ovulatory follicular wave was induced by ablation of follicles > or =6mm and treatment with prostaglandin F2alpha (PGF) on Day 10 (ovulation=Day 0). Follicle and hormone dynamics of the induced waves were compared among three age groups: young (5-6 y, n=14 waves), intermediate (10-14 y, n=16), and old (> or =18, n=15). During the common-growth phase of the induced wave (Days 12-17), diameter of the future ovulatory follicle was not different among ages, but the young group had more (P<0.05) follicles that reached > or =10mm. The number was correlated (r=+0.7; P<0.0001) within mares between consecutive interovulatory intervals, indicating repeatability. Concentrations of LH increased in all age groups during Days 12-17, but were greatest (P<0.002) in the young group and continued to be greater (P<0.0001) throughout the ovulatory LH surge. During several days before Day-1, there were no age-related effects on systemic estradiol concentrations, diameter of the preovulatory follicle, or B-mode echotexture or color-Doppler signals of blood flow in the follicle wall. Interpretations were: (1) greater number of follicles in the young group reflected a greater follicle reserve, (2) greater LH concentrations throughout the ovulatory surge in the young group reflected a more positive response to an extraovarian/environmental influence after removal of the negative effect of progesterone, and (3) lower LH concentrations in the older groups were adequate for the preovulatory changes in the follicle.
Ginther
O J
OJ
Eutheria Foundation, Cross Plains, WI 53528, USA. ginther@svm.vetmed.wisc.edu
Gastal
M O
MO
Gastal
E L
EL
Jacob
J C
JC
Beg
M A
MA
D000375:Aging / Q000502:physiology*; D000818:Animals; D015237:Dinoprost / Q000008:administration & dosage*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood*; D006736:Horses / Q000502:physiology*; D007986:Luteinizing Hormone / Q000097:blood*; D006080:Ovarian Follicle / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology*; D010060:Ovulation / Q000502:physiology; D010062:Ovulation Induction / Q000662:veterinary; D018615:Ultrasonography, Doppler, Color / Q000662:veterinary
D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D015237:Dinoprost