Effect of adding reduced glutathione during insemination on the development of porcine embryos in vitro

This study evaluated the effect of adding reduced glutathione (GSH)during sperm washing and insemination on the subsequent fertilization dynamics and development of IVM porcine oocytes. Follicular oocytes were matured in vitro in NCSU 23 medium with porcine follicular fluid, cysteine and hormone supplements for 22 h. They were then matured in the same medium but without hormones for another 22 h. Matured oocytes were stripped of cumulus cells and co-incubated with frozen-thawed spermatozoa for 5 h. Putative embryos were cultured in NCSU 23 with BSA for either 7 h to examine fertilization parameters or 6 d to evaluate cleavage (2 d) and blastocyst rates. In Experiment 1, GSH was added to the insemination medium at 0, 0.125, 0.25 or 0.5 mM. The presence of GSH during insemination did not affect (P > 0.05) rates of penetration, polyspermy, male pronuclear formation or cleavage, but did increase (P < 0.05) blastocyst formation rates when added at concentrations of 0.125 (36%) and 0.25 mM (34%) compared with that of the control (0 mM; 19%). However, the numbers of inner cell mass and trophectoderm cells of blastocysts were unaffected by GSH treatment (P > 0.05). The presence of GSH during insemination was found not to significantly increase intracellular glutathione concentrations of oocytes (P > 0.05). In Experiment 2, addition of GSH (0.25 mM) during sperm washing did not affect cleavage or blastocyst formation rates or cell numbers (P > 0.05). In conclusion, the presence of GSH during insemination improves the developmental competence of IVM pig oocytes in a dose-dependent manner. (C) 1999 by Elsevier Science Inc.