Controlling interrelationships of progesterone/LH and estradiol/LH in mares.
The interrelationships of progesterone, estradiol, and LH were studied in mares (n=9), beginning at the first ovulation (Day 0) of an interovulatory interval. An increase in mean progesterone concentrations began on Day 0 and reached maximum on Day 6, with luteolysis beginning on Day 14. A common progesterone threshold concentration of about 2 ng/ml for a negative effect on LH occurred at the beginning and end of the luteal phase. Progesterone and LH concentrations decreased at a similar rate from Day 6 until the onset of luteolysis on Day 14, consistent with a decreasing positive effect of LH on progesterone. Concentrations of LH during the increase in the ovulatory surge consisted of two linear regression segments involving a rate of 0.4 ng/ml/day for Days 14-22 and 1.8 ng/ml/day for Day 22 to 1 day after the second ovulation. The end of the first segment and beginning of the second segment was 2 days before ovulation and was the day the ovulatory estradiol surge was at a peak.
Ginther
O J
OJ
Eutheria Foundation, Cross Plains, WI 53528, USA. ginther@svm.vetmed.wisc.edu
Utt
M D
MD
Bergfelt
D R
DR
Beg
M A
MA
D000818:Animals; D004958:Estradiol / Q000097:blood*; D005260:Female; D006736:Horses / Q000097:blood* / Q000502:physiology*; D016014:Linear Models; D007986:Luteinizing Hormone / Q000097:blood*; D003341:Luteolysis / Q000502:physiology; D010060:Ovulation / Q000502:physiology*; D010061:Ovulation Detection / Q000662:veterinary; D011374:Progesterone / Q000097:blood*
D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone