THE SOURCE OF OVARIAN OESTRADIOL AND ANDROSTENEDIONE IN THE SHEEP DURING THE LUTEAL PHASE

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Abstract
The secretion of estradiol and androstenedione was investigated in sheep by cannulating both ovarian veins in situ. The mean ovarian blood flow (ml/min .+-. SE) was significantly higher on the side containing the corpus luteum (7.67 .+-. 1.36) than on the contralateral side (4.93 .+-. 0.85). The mean secretion (ng/min .+-. SE) of estradiol (1.09 .+-. 0.36) and androstenedione (1.52 .+-. 0.16) was higher on the side containing at least one large follicle (diameter > 4 mm) than on the contralateral side (0.19 .+-. 0.05 and 0.62 .+-. 0.21, respectively). The secretion of estradiol was unchanged following enucleation of the corpus luteum but fell to very low levels (0.062 .+-. 0.022 ng/min) after enucleation of follicles diameter > 4 mm. The secretion of androstenedione fell significantly after enucleation of both corpus luteum and large follicles. During the luteal phase in the sheep estradiol is secreted virtually exclusively by the largest non-atretic Graafian follicle. Androstenedione in contrast arises from both follicle, corpus luteum and possibly stroma.