Myeloperoxidase as an indicator of endometritis in the mare: preliminary results

Diagnosis of endometritis in the mare is routinely based on the presence of polymorphonuclear cells (PMNs) on endometrial smears. Studies show a relation between PMNs and myeloperoxidase (MPO), an enzyme released by PMNs during degranulation or after cell lysis, in many fluids and tissues. The aims of this study were to assess the presence and concentration of MPO in the mare’s uterus, and to investigate its relation with PMNs. Thirty-six cycles from 28 mares (ages ranging from 6 to 22 years) were used. Endometrial cytological samples were obtained with a small volume uterine flush and either a uterine cotton swab or a cytobrush, when a follicle >35 mm was observed by ultrasound. The smears were stained with Diff-QuickÒ and one or more PMNs per field (400·) was diagnosed as endometritis. The supernatant of the flushes was used to measure MPO concentration with a specific equine MPO ELISA assay. Our results showed the presence of MPO in the equine uterus during oestrus (mean = 2839 + 2785). MPO concentrations were signifi- cantly (p < 0.05) higher in samples with positive cytological results. Occasionally, some samples with negative cytological results showed high MPO concentration, but the opposite was never observed. Clinical signs of endometritis are not always present, or they may be delayed. An early diagnostic improves the success of treatment. Our results show that high quantities of MPO in endometrial samples indicate the presence of PMNs. Further studies are needed to determine if MPO concentration could be routinely used as a tool of early detection of endometritis.