STEROID CONTENT OF THE EQUINE OVARY DURING THE REPRODUCTIVE CYCLE

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Abstract
SUMMARY Follicular fluid from individual follicles was collected from nine mares in oestrus and the concentration of the following steroids determined by gas—liquid chromatography: progesterone, 17α-hydroxyprogesterone, androstenedione, 19-norandrostenedione, epitestosterone, oestrone and oestradiol. The most vascular follicles, which were probably those destined to ovulate, tended to have the highest steroid concentrations. In these vascular follicles oestradiol was the main steroid found with an average concentration of 151 μg/100 ml. In two out of three samples of follicular fluid taken from the mares with recent ovulations, oestradiol was present in large quantities. The corpora lutea from these mares contained the following steroids: progesterone (average: 1973 μg/100 g), 17α-hydroxyprogesterone (average: 65 μg/100 g), 20α-dihydroprogesterone (average: 249 μg/100g), pregnenolone (average: 33 μg/100 g). Pregnenolone was not detected in any of the samples of follicular fluid examined. A pool of eight mid-cycle corpora lutea contained the same four steroids as those in newly formed corpora lutea but, in addition, oestradiol was detected in the order of 4 μg/100 g.

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