Abstract
Even if mares continue to breed up to an advanced age, in aging mares reproductive failure is quite common. Subclinical endometritis, which occurs more often in aging mares than in younger counterparts, may cause prolongation or shortening of the inter-estrus period or the corpus luteum lifespan. We hypothesized that during subclinical endometritis the secretion of selected arachidonic acid metabolites may differ in aging mares compared to younger females. To verify this thesis, ex vivo organ cultures of endometrium were established with subsequent measurements of concentrations of prostaglandin E2 (PGE2), 6-keto-PGF1α and both leukotrienes (LTs), LTB4 and LTC4 in the culture supernatants. The endometrial biopsies were obtained from 82 mares of known breeding history. This study revealed that the concentrations of the selected arachidonic acid metabolites, which act both as immunological mediators and endocrine modulators in the reproductive organs, depends on the mares' ages. Spontaneous endometrial secretion of PGE2, 6-keto-PGF1α and LTC4 was increased in mares aged 16-23 years that suffered from subclinical endometritis, compared with control counterparts. Moreover, secretion of these metabolites was higher in endometritis-positive mares aged 16-23 years than in younger females. We conclude that advanced age in mares further disturbs the immuno-endocrine balance in endometritis-positive mares.