Studies on the composition and antibacterial activity of uterine fluid from mares.

This article discusses a research on the composition and antibacterial properties of uterine fluid in mares during oestrus and dioestrus. Forty samples from infection-resistant mares were examined for their influence on phagocytosis by neutrophils and peroxidase activity.

Objective and Methodology

• The objective of this study was to explore the composition and antibacterial activity of uterine fluid from mares.
• 40 samples of uterine fluid were taken during oestrus and dioestrus of successive cycles from 4 mares, chosen because they had shown resistance to bacterial infection of the uterus.
• The fluid samples were analysed for peroxidase activity, ability to influence phagocytosis by polymorphonuclear neutrophils, fluid volumes, protein concentrations and serum oestrogen values.

Findings

• It was found that uterine fluid volumes, protein concentrations, and serum oestrogen values were similar during oestrus and dioestrus.
• Serum progesterone concentrations were found to be lower during oestrus.
• When equine neutrophils were exposed to a genital strain of Streptococcus zooepidemicus, neutrophil phagocytosis was significantly higher when cells were incubated with oestrous uterine fluid compared to dioestrous fluid.
• The addition of 5% serum to the incubation medium increased the rates of in vitro phagocytosis, but these did not differ between oestrus and dioestrus.
• However, rates of phagocytosis with and without serum were not correlated with serum oestrogens or progesterone, or with protein content of uterine fluid.
• In the absence of infection, the peroxidase activity of uterine fluid was negligible throughout the oestrous cycle.
• Peroxidase levels did not significantly correlate with serum oestrogens or progesterone, but a significant correlation was found between peroxidase and protein concentration of uterine fluid.
• Bacterial or fungal infections led to an increased protein content in the uterine fluid, and usually marked increases in peroxidase, which probably derived from the visibly obvious populations of leucocytes.