Secretion of prostaglandins and leukotrienes by endometrial cells in cows with subclinical and clinical endometritis

Abstract

The aims of this study were (1) to measure the secretion of prostaglandin F2α (PGF2α), prostaglandin E2 (PGE2), leukotriene B4 (LTB4), and leukotriene C4 (LTC4) by endometrial cells collected by a cytobrush from healthy cows and cows with subclinical and clinical endometritis in the fourth week postpartum, and (2) to evaluate the relationship between the mediators' levels of secretion and the number of polymorphonuclear neutrophils (PMNs) in the uterine smears of cows with subclinical endometritis. The study included cows without any signs of clinical endometritis (n = 63) and cows with clinical endometritis as a positive control (ENDOM, n = 12). Two different threshold ratios (>5% and >18% of PMNs) were used to categorize the cows without clinical signs as with or without cytologic endometritis (CE). Considering the first or second threshold, the animals with CE were included in group CE POS I or CE POS II, whereas the healthy cows were assigned to group CE NEG I or CE NEG II, respectively. The prevalence of CE was 68.25% (42/63) and 57.14% (36/63) according to the first and second thresholds, respectively. The highest level of secretion of all of the measured mediators occurred in the ENDOM group and differed significantly (P < 0.05) from the CE POS and CE NEG groups, regardless of the threshold. PGF2α secretion in the CE POS II group (1629 pg/mL) was significantly lower (P < 0.05) when compared with the CE NEG II group (2797 pg/mL), whereas there was no significant difference between the CE POS I and CE NEG I groups. PGE2 secretion differed between both groups with CE; higher concentrations were measured in the CE POS II group (6.68 ng/mL) when compared with the CE POS I (2.4 ng/mL) and CE NEG II (2.37 ng/mL) groups (P < 0.05). No significant differences were observed in the LTB4 and LTC4 secretion between the CE POS and CE NEG groups, considering both thresholds. It seems that CE does not fully mimic the inflammatory cascade associated with clinical signs. The response in the subclinical cases was limited to enhanced production of PGE2, which was particularly well-pronounced in cows with high numbers of PMNs (>18%) in the endometrial scrapings.

Keywords: Cattle; Endometritis; Leukotrienes; Prostaglandins.