Pulsatile Release of LH and Secretion of Ovarian Steroidsin Sheep During the Luteal Phase of the Estrous Cycle

Publisher Website
Google Scholar
Abstract
The concentration of LH [luteinizing hormone] and progesterone in jugular venous plasma and the secretion of steroids by the ovary were measured every 10 min for 2 h on days 12, 14 and 16 of the estrous cycle in 5 ewes with utero-ovarian autotransplants. A pulse of LH occurred about once every 2 h, when the concentration rose from a basal level of 0.57 .+-. 0.08 ng/ml to a peak of 2.97 .+-. 0.57 ng/ml. Within 5 min of the pulse of LH, the secretion of estradiol (an exclusive product of the follicle) rose rapidly from a basal level of 0.75 .+-. 0.12 ng/min to reach a peak value of 2.16 .+-. 0.33 ng/min in about 30 min. In contrast, the secretion of progesterone from the corpus luteum, and the concentration of progesterone in the peripheral plasma changed very little following the pulse of LH. The secretion of androstenedione, which arises from the follicle and corpus luteum, increased from 3.03 .+-. 0.75 ng/min to 7.85 .+-. 1.78 ng/min by 30 min after the pulse of LH. The follicle, and possibly the stroma, respond rapidly to episodic fluctuations in the concentration of LH and are probably involved in the negative feedback loop between the ovary and the hypothalamic pituitary system. The fluctuations in the secretion of progesterone from the corpus luteum, on the other hand, are unrelated to pulses of LH.