Influence of estrogen on antibacterial and immunoglobulin secretory activities of uterine fluids from ovariectomized mares.

The research focused on the impact of hormones estrogen and progesterone on the antibacterial activity and immunoglobulin concentrations within the uterus of mares. Surprisingly, neither of the hormones demonstrated an increase in the activity of uterine and blood serum fluids against a specific bacteria, differing from previous studies on sexually intact mares.

Research Procedure

• The study was performed on 6 mixed-breed mares which were ovariectomized (their ovaries were removed).
• Two in vitro experiments were conducted, examining uterine fluid and blood serum.
• The fluids collected were analyzed on days 3, 5, and 8 of hormonal treatment while blood serum was analyzed only on day 8 of treatment.
• Antibacterial assays were employed to determine the inhibitory impacts on Streptococcus zooepidemicus, a bacteria commonly affecting horses.
• Single radial immunodiffusion methods were used to quantify amounts of IgA and IgG immunoglobulins in uterine fluid and blood serum on several treatment days.

Findings and Observations

• Contrary to expectations, neither estrogen nor progesterone heightened the antibacterial activity of uterine fluid or serum against S zooepidemicus bacteria.
• The control solution (Hanks’ balanced salt solution with 1.0% gelatin (HBSSG)) had significantly fewer bacteria than the uterine fluids.
• Bacterial numbers in uterine fluids and serum outpaced HBSSG controls for both treatments by 50%.
• Both fluids, particularly serum, facilitated significantly more growth of S zooepidemicus compared to HBSSG when incubated for 0, 2, and 4 hours.
• The results contradicted previous observations of antibacterial activity in the uterus of sexually intact mares during an estrous cycle, wherein bacterial count was significantly reduced in the uterine fluid during diestrus.
• Comparisons between serum and uterine fluid immunoglobulin A (IgA) and immunoglobulin G (IgG) concentrations were insignificant, although overall, IgA concentration in the uterus surpassed the concentration in serum.

Conclusions

• This research contributes to the understanding of hormonal effects on the protective measures of the uterus against bacterial infections, specifically in mares.
• However, the results raised questions about the role of estrogen and progesterone, as they did not enhance the antibacterial activity as expected.
• Be it that, more research is needed to clarify these effects, especially given the contrasting findings from past research with sexually intact mares.