Etiopathogenesis of equine intrauterine fluid accumulation
Beitrag zur Ätiopathogenese der intrauterinen Flüssigkeitsansammlung (IUF, Hydromucometra) beim Pferd
Özgen S, Schoon H A, Aupperle H, Sieme H, Klug E
DOI: 10.21836/PEM20020614
Year: 2002
Volume: 18
Issue: 6
Pages: 594-599
In order to achieve further information on the etiology and the pathogenesis of intrauterine fluid accumulations in mares eight mares with fluid accumulations and seven mares with no known reproductive pathology were observed throughout an entire estrous cycle. Examinations were performed using palpation and ultrasonography via the rectum. Blood was taken throughout the cycle for 17b-estradiol and progesterone determination. In addition biopsy samples were obtained from each mare on day 0 (day of ovulation) 5, 10, 13, 16, 19 and 21 postovulation and examined with different histological methods (light microscopy, morphometry, immunohistochemistry: ER, PR, Ki-67 antigen) and enzyme immunoassay (PGF2a). Uterine swabs for microbiological evaluation were taken before first biopsy. Ultrasonographically detected fluid accumulations were more often in old barren mares than in young mares. In most cases uterine free fluid appeared at the end of the luteal phase and disappeared around ovulation. Maximal volumes of fluid were estimated during early estrus. Histomorphometrical results indicate hypersecretory activity of the endometrial glandular structures. The length of interovulatory interval of IUF-mares (mares with intrauterine fluid accumulation) was reduced. Progesterone concentrations in mares accumulating fluid were significantly lower than in control mares during the entire luteal phase. In both groups the amount of PGF2a in the endometrium at the early stage of diestrus was low. Bacteria were significantly more often cultured from endometrial swab samples taken from mares with detectable uterine fluid than from mares with no fluid indicating „susceptibility“ to bacterial contamination of the uterus. Estrogen and progesterone receptor immunoreactivity in IUF-mares was higher than in control mares. The progesterone profile and endometrial PGF2a of mares with fluid collections support the hypothesis that the shortened length of interovulatory interval was due to primary luteal insufficiency rather than uterine-induced luteolysis. Probably due to the lacking of luteal progesterone in IUF-mares the progesterone mediated suppression of the steroid receptors is impeded and glandular cell differentiation is affected to secretion.