52 Difference of Seminal Plasma Proteins in Good- and Poor-Freezability Boar Ejaculates

Abstract

Seminal plasma is the semen components that maintain sperm metabolism, pH and osmolality. Fibronectin (FN1) and glutathione peroxidase (GPX5) are the seminal plasma proteins that play an important role on the boar sperm functions. The purpose of the present study was to determine the differences in GPX5 and FN1 contents in the boar semen having good, moderate, and poor freezability. A total of 38 ejaculates from 25 boars with proven fertility were included in the experiment. All the ejaculates included in the study had >70% subjective motility, >75% normal morphology, >75% sperm viability, and volume >100 mL per ejaculate. The semen was collected through semen collection bag with filter and split into 2 portions. The first portion was prepared for the evaluation of seminal plasma proteins (i.e. GPX5 and FN1) and the second portion was cryopreserved and evaluated for post-thaw semen qualities. The seminal plasma samples were collected in cryotube and plug into liquid nitrogen. The samples was stored at –80°C before protein extraction. After thawing, the ejaculates were classified into 3 groups according to their post-thawed sperm motility: poor (14.6 ± 3.9%), modersate (28.5 ± 4.1%), and good (64.0 ± 8.7%) freezability. The amounts of GPX5 and FN1 proteins were evaluated through Western blot analysis. The normalized quantity of proteins was compared among groups by one-way ANOVA. The normalized level of FN1 in seminal plasma was higher in good- than in poor-freezability groups (8.0 ± 0.8% v. 5.7 ± 0.7%, respectively; P < 0.05), but did not differ significantly compared with that of the moderate-freezability group (7.5 ± 0.8%; P > 0.05). The levels of GPX5 in good-, moderate-, and poor-freezability groups were 14.7 ± 3.0%, 16.8 ± 3.2%, and 10.9 ± 3.0%, respectively (P > 0.05). The level of FN1 in seminal plasma was significantly correlated with the post-thaw sperm progressive motility (r = 0.38, P = 0.01), total motility (r = 0.37, P = 0.02), and the proportion of bent tail sperm (r = –0.33, P = 0.04). The level of GPX5 was not correlated with any of the post-thaw sperm qualities (P > 0.05). However, the levels of GPX5 was positively correlated with FN1 (r = 0.40, P = 0.01, n = 38). It can be concluded that FN1 in seminal plasma can be used as a marker of sperm freezability in boar.