ALKALINE PHOSPHATASE ACTIVITY IN STALLION SEMINAL PLASMA AND SPERM EXTRACTS

Alkaline phosphatase (AP) is an ubiquitous enzyme active in many tissues; it is also present in the male genital tract and seminal fluids. This work aimed to determine the activity of AP in stallion seminal plasma (SP) and spermatozoa extracts (SE) as well as possible relationships with sperm quality parameters. Semen was collected from nine fertile stallions by a Missouri artificial vagina; semen handling and AP activity assay were performed as described by Bucci et al. (Andrology, 2014, 2, 100). An ANOVA test was used to define differences between horses and a Pearson’s test was used to establish the correlations among parameters. Our results show that AP activity in SP is significantly higher than in SE (63.81 +-48 lmol/mg protein/ min and 4.24 +- 1.9, respectively, p < 0.05); no differences among stallions were found on SP AP activity (except for one subject that differed from all the others), while some stallions differed in SE AP activity (p < 0.05). AP activity in SE and total motility, progressive motility, viability and mitochondrial sperm activity were negatively correlated (p < 0.05). Sperm concentration and AP activity in SP were not correlated with the other parameters. In conclusion our data suggest that AP activity in SP is not indicative of sperm quality; in contrast, AP activity in SE could be an indicator of the quality (in terms of motility, viability and mitochondrial activity) of stallion spermatozoa. Further studies could determine the physiological role of AP in SP and SE and would assess its value as a predictor of fertility in stallion.