Reproduction Abstracts

Introduction: Seminal PDC-109, most abundant protein in bulls, destabilizes sperm membrane by causing efflux of cholesterol. This detrimental effect is minimized to some extent by addition of egg yolk (EY) in extender. Knocking-down of free floating PDC-109 protein by antibodies (Ab) can be another method not yet reported. Therefore, a study was designed to assess the effect of antibodies-mediated sequestration of PDC-109 protein as compared to EY on minimization of cryoinjury to bull sperm.

Materials and methods: Anti-PDC-109 raised in rabbits were isolated, purified, and added in ejaculates. Cholesterol content, viability, and cryoinjury as manifested by chlortetracycline assay at different stages of cryopreservation as progressive series, were evaluated (n=6). Three groups were: Gr I, control, ejaculates processed in EY+tris-glycerol (TG) -extender (EYTG); Gr II, ejaculates collected directly in EY+TG; efficacy of EY was tested from this group; Gr III, Ab+EY+TG, processed for cryopreservation.

Results and discussion: The pre-freeze and post-thaw cholesterol content (μg/100 million spermatozoa) and viability were significantly higher in antibodies treated group as compared to Gr I and II. The chlortetracycline assay revealed significantly higher non capacitated spermatozoa in Gr III and conversely, mean values for pre-freeze spermatozoa showing pattern B and AR were significantly lower in Gr III than other two groups. It can be concluded that sequestration of PDC-109 protein by antibodies and EY increases tolerance of spermatozoa to cryoinjury. This study underlines that cryoprotection of spermatozoa can be achieved much more efficiently by addition of antibodies at processing.