Abstract: 29

CRYOPRESERVATION OF BOVINE SEMEN DECREASES ANTIOXIDANT DEFENSES IN SPERMATOZOA.

Jean-François Bilodeau¹ , Suvro Chatterjee¹ , Marc-André Sirard^{2 *}, Claude Gagnon^{1 *}
Urology Research Laboratory, Royal Victoria Hospital and McGill University, Montreal, PQ, Canada. ¹
Département des sciences animales, Université Laval, PQ, Canada. ²

Cryopreservation of bovine semen by the artificial insemination industry for delayed insemination lead to a decreased sperm viability and fecundity when compared to fresh semen. In this work, we have investigated the combined effects of extending the semen several hundred-folds and freezing / thawing on the level of antioxidants in spermatozoa. We have found that bovine spermatozoa have low enzymatic defenses against H₂O₂. Indeed, very low levels of glutathione peroxidase (< 6 mU/mg protein) and no catalase were detected, while significant levels of GSH (560 pmol/mg) and superoxide dismutase (SOD) (284 U/mg) were measured. Spermatozoa were isolated using a Percoll gradient to avoid contamination from seminal plasma. In contrast to spermatozoa, seminal plasma showed relatively high levels of GPx and catalase activity. Then, we have studied the effect of cryopreservation of semen diluted in Tris-citrate egg Yolk glycerol (EYTG) on the level of SOD and the level of total GSH, two very important antioxidant defenses in bovine spermatozoa. We have clearly shown that the freeze/thaw process reduces significantly GSH level by 78% and SOD activity by 50 % in spermatozoa (n=5). This reduction of the level of GSH was indirectly associated with oxidative metabolism since an incubation of spermatozoa under aerobic condition in EYTG extender decreased rapidly intracellular levels of GSH when compared to an incubation under limited oxygen supply. Therefore the latter results strongly suggests the occurrence of an oxidative stress during the cycle of freeze/thaw that may partly explain the observed deleterious effect on fecundity of cryopreserved semen. This work was supported by NSERC and Semex Canada.

    This abstract is being presented on Sunday, August 1 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.