Characterization of alkaline phosphatase activity in seminal plasma and in fresh and frozen-thawed stallion spermatozoa.

The research investigates the behaviour and impact of alkaline phosphatase (AP) in horse semen, assessing its activity in fresh ejaculate and frozen-thawed sperm. Findings reveal seminal plasma is the main source of AP activity, and the enzyme’s activity may correlate with sperm quality. They also observed a decrease in AP activity in sperm after freezing and thawing.

Objective of the Research

• The research aimed at understanding the activity and role of alkaline phosphatase (AP) in horse reproductive physiology. The research thus investigated AP activity in fresh ejaculate and frozen-thawed horse sperm and examined any possible relationship between AP activity and sperm quality parameters.

Main Findings

• The main source of AP activity is seminal plasma, with sperm extracts showing significantly less AP activity.
• AP activity at a physiological pH (7.0) was found to be significantly lower than at pH 8.0, including the optimal AP pH (pH 10.0).
• AP does not affect the ability of sperm to bind to oocytes (a critical interaction for successful fertilization).
• Seminal plasma AP exhibited thermal stability, similar behavior to AP isoforms found in bones.
• Positive correlations were identified between AP activity in seminal plasma and sperm concentration, implying a possible role of AP in sperm production or movement.
• Negative correlations were found between both seminal plasma AP activity and AP activity from spermatozoa extracts with seminal plasma protein content, suggesting a competitive or inverse relationship between the components.

Significance on Frozen-Thawed Samples

• There was a significant decrease in AP activity from sperm extracts in frozen-thawed samples compared to fresh samples. A concurrent decrease in sperm quality parameters was also noted.
• The researchers identified a positive correlation between seminal plasma AP activity (measured at pH 10) and the viability of frozen-thawed sperm. This suggests that the AP activity could serve as a predictor of sperm survival rates after freezing and thawing – a common practice in animal breeding and assisted reproduction techniques.
• These findings provide valuable insights into the behavior of AP in semen, its impact on sperm quality, and potential implications for the successful preservation of sperm in the veterinary and animal breeding sectors.