Oxytocin-induced PGF2alpha release in mares with and without post-breeding delayed uterine clearance

The aim of the present study was to evaluate within 24 h post-ovulation oxytocin-induced PGF(2alpha) release in mares with and without post-breeding delayed uterine clearance (DUC). Twenty-one of 34 mares with a variable amount of intrauterine fluids accumulation were considered to be affected by delayed uterine clearance (DUC group), while the other 13 mares did not show any uterine fluid accumulation, and were considered as controls (WDUC group). Both DUC and WDUC mares were administered with 20 IU oxytocin i.m. 90 min after the ultrasound examination performed 24 h after breeding. Immediately before, 5 and 10 min after oxytocin administration, blood samples were collected for 15-ketodihydro-PGF(2alpha) (PG-metabolite), 17beta-estradiol, and progesterone analysis. Ultrasonography performed 24 h after oxytocin treatment showed a complete uterine clearance in all DUC mares. The oxytocin-induced PG-metabolite increase was detected in 71.4% DUC mares compared with 38.5% in WDUC group, with a positive trend of release, as evidenced from 5 min after oxytocin administration. In WDUC mares, no significant differences in oxytocin-induced PG-metabolite trend of release were observed. In conclusion, the results of the present study showed the importance of PGF(2alpha) involvement in the pathogenesis of post-breeding DUC in the mare.