OVARIAN OESTROGEN LEVELS IN THE NON- PREGNANT MARE: RELATIONSHIP TO HISTOLOGICAL APPEARANCE OF THE UTERUS AND TO CLINICAL STATUS

Summary. The oestrogen levels in follicular contents have been esti¬ mated for thirty-two non-pregnant mares in different phases of the oestrous cycle, and for three sterile mares with ovarian dysfunction. The estimations were made by use of a highly specific chemical method, which permitted the separate determination of oestrone and oestradiol-17 ß. The phases of the oestrous cycle for each mare were determined by clinical observations, post-mortem examinations of the genital organs and histological investigations of the uterus. In pro-oestrus, circum¬ scribed groups of glandular ducts which are typical for this phase, but which do not seem to have been reported previously, have now been described. In the oestrous group of mares, the levels of both oestrone and oestradiol-17ß found were highly significantly elevated when com¬ pared with the values for the mares in the other phases of the cycle taken together (P<0-0005). In the anoestrous group, a significantly elevated level of oestradiol-17ß was recorded for animals with autumn follicles, when compared with the other mares in this group (P<0-05). Two mares which had persistent follicles and were placed in the metoestrous group showed elevated oestrogen values. In two cases diagnosed as cystic glan¬ dular endometritis, high oestrogen levels were encountered. In a single mare with a follicle present for a continuous period of at least 3 months(probably for more than 1 year), no oestrogens were demonstrated in the follicular fluid in spite of clinical signs of heat. In all mares except the last, oestradiol-17ß was present in large amounts, relatively to oestrone. The mean values for the total amount of follicular contents analysed were 33-8 \xg oestradiol-17ß and 2-3 ug oestrone per 100 ml(uncorrected values)