Effects of platelet-activating factor and platelet-activating factor: acetylhydrolase on in vitro post-thaw boar sperm parameters

Cryopreservation of boar sperm compromises fertility after thawing by reducing sperm longevity and inducing acrosome reaction-like changes. In an attempt to improve the post-thaw motility and acrosome integrity of boar sperm, semen was frozen using a modified Westendorf method in which the medium was supplemented with either platelet-activating factor (PAF) or a recombinant platelet-activating factor:acetylhydrolase (PAF:AH; Pafase) before or after freezing. Platelet-activating factor is a phospholipid that is present in boar semen and PAF:AH is the naturally occurring enzyme that converts PAF to biologically inactive Lyso-PAF. Addition of PAF to the cryopreservation medium improved post-thaw motility immediately after thawing and after 3h incubation at 37 degrees C (60.0+/-0.0% and 25.0+/-2.9%; mean+/-S.E.M.) compared to the control sperm (41.7+/-1.7% and 10.0+/-2.9%; P<0.05). Acrosome integrity was higher immediately after thawing and after 3 and 6h incubation at 37 degrees C when sperm were frozen in the presence of Pafase (55.7+/-3.2%, 45.7+/-3.7% and 23.0+/-3.1%), compared to the control sperm (42.7+/-1.5%, 25.7+/-5.7% and 12.3+/-2.7%) and sperm frozen in the presence of PAF (33.0+/-3.7%, 26.3+/-2.2% and 11.7+/-0.3%; P<0.05). Addition of PAF to sperm after thawing improved motility immediately post-thaw (41.6+/-2.6%), compared with addition of Pafase (23.3+/-2.2%) or the control sperm with no supplementation of the medium (26.7+/-2.2%; P<0.05). However, this beneficial effect was lost by 3h post-thaw. Supplementation of boar semen cryopreservation medium with PAF and Pafase appeared to have beneficial effects on the in vitro quality of the sperm post-thaw.