Effect of three seminal plasma proteins on pig semen freezability

The results of fertility with the application of frozen-thawed boar semen are not consistent due to between-boar variation in freezability. The objective of this work was to determine the effect of three seminal plasma proteins on freezability of boar semen: Nieman-pick disease type C2 (NPC2), cholesterol transfer in cell membrane; heat shock protein 90 alpha A1 (HSP90AA1) and Lipocalin-Type prostaglandin D synthase (PGDS-L) involves in capacitation and acrosome reaction.

Semen of six boars was frozen three times in a row and evaluated after thawing to ascertain freezability through measurement of the percentage of sperm functionally competent (SFC). One boar was selected with the highest freezability (BHF) and one with the lowest freezability (BLF) for semen collection and immediate separation of sperm from seminal plasma (SP). Four combinations of sperm and SP were incubated during three hours lowering the temperature to 17ºC before freezing, and evaluated post-thawing for morphology, membrane structural integrity, total and progressive motility, acrosome integrity, functional integrity of membrane and SFC. Protein identification was performed through SDS-PAGE and Western blot to quantify at zero and three hours of incubation time, based in volume and density band. 2x2x2 factorial arrangement in completely randomized design was performed. ANOVA and correlation analysis were performed.

two isoforms of the protein NPC2 (16 and 19 KDa) were detected. The interaction sperm x incubation time had an effect on HSP90AA1 (P < 0.01), and PGDSL (P < 0.05) levels, and did not (P > 0.05) on the levels of isoforms NPC2; SP x incubation time interaction only affected (P < 0.01) NPC2 of 19 KDa levels; SP factor did not affect the PGDS-L and HSP90AA1 levels, and the sperm factor did not affect the NPC2 of 19KDa (P > 0.05). The NPC2 of 16 KDa was affected (P < 0.01) only by incubation time, with a reduction after three hours. NPC2 of 19 KDa concentration was highest in SP of BHF combinations (P < 0.01) and it concentration decreased at the end incubation time. After of the incubation, the HSP90AA1 concentration increased (P < 0.01) in greater amounts in sperm of BLF combinations; and PGDSL concentration declined most in these same combinations. Only there was a negative correlation between the levels of HSP90AA1 and progressive motility (-0.6, P > 0.05).

The type of sperm or seminal plasma, whether high or low freezability, affected the concentration of the three seminal plasma proteins, indicating an association of these with freezability of boar semen.

Disclosure of Interest: None Declared.