Fertilizability and developmental capacity of bovine oocytes cultured individually in a chemically defined maturation medium

This study investigated effects of adding hypotaurine (HT), beta -merocaptoethanol (beta -ME), or both into a chemically defined maturation medium (TCM-199 containing 0.1% polyvinyl alcohol: PVA) on maturation, fertilization and development of individually (single) cultured bovine oocytes. Mean GSH concentration in the oocytes cultured in the medium supplemented with either beta -ME (1.11 +/-0.05 nM) or HT plus beta -ME (0.97 +/- 0.03 nM) was significantly (P < 0.05) higher than that in the medium containing PVA alone (0.75 +/- 0.03 nM). Adding -ME showed a significantly (P < 0.05) higher rate of the second metaphase stage (93.6 +/- 3.3%) than in the medium containing PVA alone (single-control) (65.2 +/- 7.9%). Adding both HT and -ME showed significantly (P < 0.05) higher rates (92.6 +/- 2.7%) of normal fertilization than did adding Hi alone (63.5 +/- 4.6%). Also, adding both HT and -ME significantly (P < 0.05) lowered the polyspermy rate than did adding HT alone. Adding either -ME or both HT and beta -ME showed no significant difference in cleavage. Blastocyst development did not improve significantly adding either HT, beta -ME or both, although beta -ME alone or HT plus beta -ME tended to result in a higher rate of blastocysts (6.4 and 6.8%, respectively) than resulted without additives (1.6%). Our results show that adding beta -ME to a chemically defined maturation medium increased the intracellular GSH level of bovine oocytes cultured individually, and can improve the maturation rate leading to the blastocyst stage throughout in vitro production. (C) 2001 by Elsevier Science Inc.