Secretion of LH, FSH and oestradiol-17 beta during the follicular phase of the oestrous cycle in the ewe.
Plasma concentrations of LH, FSH and oestradiol-17 beta were measured in blood samples taken at 15 min intervals for 48 h during the follicular phase of four Merino ewes. The amplitude of pulses of LH and the mean concentration of LH were higher at the beginning of the follicular phase, 36-24 h before the preovulatory surge of LH (amplitude 2.4 ng ml-1, mean concentration 3.9 ng ml-1), than at the end, 24-0 h before the preovulatory surge (amplitude 1.2 +/- 0.1 ng ml-1; mean concentration 1.4 +/- 0.1 ng ml-1). There was no change in the inter-pulse interval during this time (mean 74 +/- 5 min). Over the same period, oestradiol levels increased from 7-8 pg ml-1 to a peak of 10-15 pg ml-1. Mean FSH concentrations declined (36-24 h: 3.6 ng ml-1 vs 24-0 h: 1.8 +/- 0.3 ng ml-1) before rising at the time of the preovulatory surge of LH and again 24 h later. It was concluded that the biphasic response of LH to oestrogen that is seen in ovariectomized ewes may also operate during the follicular phase of the oestrous cycle in entire ewes.
Thomas
G B
GB
Animal Science Group, School of Agriculture, University of Western Australia, Nedlands.
Martin
G B
GB
Ford
J R
JR
Moore
P M
PM
Campbell
B K
BK
Lindsay
D R
DR
D000818:Animals; D004958:Estradiol / Q000097:blood* / Q000378:metabolism; D004971:Estrus / Q000097:blood* / Q000502:physiology; D004973:Estrus Synchronization; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood* / Q000378:metabolism; D005498:Follicular Phase / Q000502:physiology; D007986:Luteinizing Hormone / Q000097:blood* / Q000378:metabolism; D012756:Sheep / Q000502:physiology*; D013997:Time Factors
D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone