Influence of mare uterine tubal fluids on the metabolism of stallion sperm.

This research article focuses on the effect of mare uterine tubal fluids on the metabolism of stallion sperm, using three different experiments under various conditions and setups for aerobic and anaerobic incubation plus controlled additions of glucose and lactic acid. Conclusions drawn include how sperm motility and respiratory rates are influenced by the presence of uterine tubal fluids and the concentration of metabolic substrates.

Experiments and Methods

• Three experiments were conducted to test stallion sperm metabolism.
• In the first experiment, sperm was incubated in both aerobic and anaerobic conditions and then analyzed for motility, pH, lactic acid, glucose, fructose, and oxygen consumption.
• In the second experiment, this process was repeated with and without the addition of mare’s uterine tubal fluid.
• The third experiment was an extension of the second, with added substrates of glucose and lactic acid.

Results of Experiments

• In all experiments, sperm motility declined during incubation, with the most significant decline seen with whole semen where only minute traces of substrate (fructose) were present.
• It was found that the addition of glucose and uterine tubal fluid resulted in better maintenance of sperm motility compared to the addition of lactate.
• Paradoxically, sperm respiration rates were highest when lactate was the only substrate in the incubation medium.
• The addition of uterine tubal fluid in the incubation medium led to an increase in lactic acid accumulation and also enhanced oxygen utilization.
• When washed spermatozoa were incubated with glucose and uterine tubal fluid, less glucose was consumed in comparison to sperm incubated only in the glucose medium.

Interpretations and Conclusions

• The increase in oxygen utilization and reduction of glucose consumption when uterine tubal fluid was added suggests that there is a probable utilization of a substrate contained in the uterine tubal fluid.
• The addition of uterine tubal fluid yielded an increased oxygen consumption in both whole and washed semen samples.
• Washed spermatozoa exhibited higher respiration rates than intact sperm, and these rates were further increased when lactic acid was supplied as the sole substrate.

Significance

• The study provides an expanded understanding of equine sperm metabolism in relation to the presence of uterine tubal fluid.
• The results might shed light on the substrates sperm employ for energy, their physiological processes during fertilization and provide insights for advancements in equine artificial insemination practices.