Seminal carnitine and acetylcarnitine content and carnitine acetyltransferase activity in young Maremmano stallions.

This study documents the reproductive traits, seminal carnitine and acetylcarnitine content, and the activity of the enzyme carnitine acetyltransferase in young Maremmano stallions. The research points to a potential role for carnitine in male fertility, with significant correlations observed between levels of these metabolites and sperm count and quality.

Research Objectives and Methods

• The study measured the reproductive characteristics, seminal carnitine and acetylcarnitine content, and carnitine acetyltransferase activity of 25 young Maremmano stallions.
• Semen was collected from these stallions twice, once in November and once in January, with two ejaculates collected an hour apart each time.
• Several parameters were evaluated, such as the total number of motile and morphologically normal sperm cells (TMMNS) and the number of progressively motile sperm cells at the time of collection and during storage at 4°C.
• Seminal carnitine (LC), acetylcarnitine (AC), pyruvate, and lactate levels were measured using spectrophotometric methods, while carnitine acetyltransferase activity was measured using radioenzymatic methods.

Results

• The researchers found no significant differences in the reproductive and biochemical characteristics between the November and January collections. Consequently, they combined data from the first and second ejaculates.
• Significant differences were observed between the first and second ejaculates in several parameters, including sperm count, total number of sperm cells per ejaculate, the proportion of progressively motile sperm cells, and TMMNS.
• LC and AC were significantly higher in the first ejaculate than the second, while the pyruvate and the ratio of pyruvate to lactate were higher in the second ejaculate.
• Seminal plasma AC and LC concentrations were higher in the first ejaculate, while the pyruvate to lactate ratio was higher in the second ejaculate.

Correlation and Pointers

• The study also found positive correlations between LC, AC, and sperm concentration, and between AC and TMMNS. Additionally, lactate levels in raw semen were linked to progressively motile spermatozoa after storage.
• In the second ejaculate, significant correlations were observed between the AC/LC ratio in raw semen and progressively motile spermatozoa after 48 and 72 hrs of refrigeration.
• AC levels were also correlated with lactate concentration.
• The positive correlation between LC, AC, and sperm count, and between AC and TMMNS, suggests that carnitine could potentially serve as a marker for semen quality.
• The correlation between the AC/LC ratio and progressive sperm motility after refrigeration suggests that carnitine may play a role in preserving sperm viability during in vitro storage.