title: Characterization of alkaline phosphatase activity in seminal plasma and in fresh and frozen-thawed stallion spermatozoa.
abstract: Alkaline phosphatase (AP) has been studied in several situations to elucidate its role in reproductive biology of the male from different mammalian species; at present, its role in horse sperm physiology is not clear. The aim of the present work was to measure AP activity in seminal plasma and sperm extracts from freshly ejaculated as well as in frozen-thawed stallion spermatozoa and to verify whether relationship exists between AP activity and sperm quality parameters. Our data on 40 freshly ejaculated samples from 10 different stallions demonstrate that the main source of AP activity is seminal plasma, whereas sperm extracts contribution is very low. In addition, we found that AP activity at physiological pH (7.0) is significantly lower than that observed at pH 8.0, including the optimal AP pH (pH 10.0). Alkaline phosphatase did not exert any effect on sperm-oocyte interaction assessed by heterologous oocyte binding assay. Additionally, we observed a thermal stability of seminal plasma AP, concluding that it is similar to that of bone isoforms. Positive correlations were found between seminal plasma AP activity and sperm concentration, whereas a negative correlation was present between both spermatozoa extracts and seminal plasma AP activity and seminal plasma protein content. A significant decrease in sperm extract AP activity was found in frozen-thawed samples compared with freshly ejaculated ones (n = 21), concomitantly with the decrease in sperm quality parameters. The positive correlation between seminal plasma AP activity measured at pH 10 and viability of frozen-thawed spermatozoa suggests that seminal plasma AP activity could be used as an additional predictive parameter for stallion sperm freezability. In conclusion, we provide some insights into AP activity in both seminal plasma and sperm extracts and describe a decrease in AP after freezing and thawing.
authors.affiliation: Department of Veterinary Medical Sciences (DIMEVET), Ozzano dell'Emilia, Bologna, Italy. Electronic address: diego.bucci3@unibo.it.
authors.forename: Diego
authors.initials: D
authors.lastname: Bucci
authors.affiliation: Department of Veterinary Medical Sciences (DIMEVET), Ozzano dell'Emilia, Bologna, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Giaretta
authors.affiliation: Department of Veterinary Medical Sciences (DIMEVET), Ozzano dell'Emilia, Bologna, Italy.
authors.forename: Marcella
authors.initials: M
authors.lastname: Spinaci
authors.affiliation: National Institute of Assisted Reproduction (INFA), Cadriano, Bologna, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Rizzato
authors.affiliation: Department of Veterinary Medical Sciences (DIMEVET), Ozzano dell'Emilia, Bologna, Italy.
authors.forename: Gloria
authors.initials: G
authors.lastname: Isani
authors.affiliation: National Institute of Assisted Reproduction (INFA), Cadriano, Bologna, Italy.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Mislei
authors.affiliation: Department of Veterinary Medical Sciences (DIMEVET), Ozzano dell'Emilia, Bologna, Italy; National Institute of Assisted Reproduction (INFA), Cadriano, Bologna, Italy.
authors.forename: Gaetano
authors.initials: G
authors.lastname: Mari
authors.affiliation: Department of Veterinary Medical Sciences (DIMEVET), Ozzano dell'Emilia, Bologna, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Tamanini
authors.affiliation: Department of Veterinary Medical Sciences (DIMEVET), Ozzano dell'Emilia, Bologna, Italy.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Galeati
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism*; D000818:Animals; D015925:Cryopreservation / Q000662:veterinary*; D006736:Horses; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008297:Male; D012661:Semen / Q000201:enzymology*; D012662:Semen Preservation / Q000379:methods / Q000662:veterinary*; D013076:Sperm Count; D013081:Sperm Motility; D013084:Sperm-Ovum Interactions / Q000502:physiology; D013094:Spermatozoa / Q000201:enzymology* / Q000502:physiology
chemical_list: D000469:Alkaline Phosphatase
keywords: Alkaline phosphatase; Freezing and thawing; Horse sperm; Seminal plasma; Sperm extract