The phagocytic function of blood-derived polymorphonuclear neutrophils after administration of dexamethasone for the modulation of post-breeding endometritis in the mare

Persistent breeding-induced endometritis is a major cause of subfertility in the mare. Most widely applied treatment strategies involve mechanical removal of accumulated uterine fluid via lavage and administration of ecbolic agents such as oxytocin. Recently, corticosteroids administered at the time of breeding have been reported to increase fertility rates in mares susceptible to persistent breeding-induced endometritis by reducing the degree of uterine edema and intraluminal fluid accumulation. Few studies, however, have examined the potential negative effects of corticosteroids in this context, particularly those associated with impaired immunity by altering the function of polymorphonuclear neutrophils (PMNs). The objective of this study was to examine the effect of corticosteroids on the phagocytic ability of PMNs. In this study, six mares, each serving as their own control, were administered 50 mg dexamethasone IV when their ovary contained a 30-35 mm follicle in the presence of uterine edema. A blood sample was obtained before and 24 hours after treatment. The function of PMNs was examined by flow cytometry, measuring the ability of PMNs to bind and phagocytose bacteria in vitro. Results showed no significant difference (P >0.05) in the ability of PMNs to phagocytose bacteria following treatment with dexamethasone versus the control samples. It was concluded that corticosteroids can be administered as adjunctive treatment for the modulation of breeding-induced endometritis, with no significant alteration of PMN function that could predispose the mare to secondary infections. The efficacy of dexamethasone treatment to modulate breeding-induced endometritis was not investigated.