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

This study investigated effects of adding hypotaurine (HT), beta -merocapto ethanol (beta -ME), or both into a chemically defined maturation medium (TC M-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 eithe r beta -ME (1.11 +/-0.05 nM) or HT plus beta -ME (0.97 +/- 0.03 nM) was sig nificantly (P < 0.05) higher than that in the medium containing PVA alone ( 0.75 +/- 0.03 nM). Adding <beta>-ME showed a significantly (P < 0.05) highe r rate of the second metaphase stage (93.6 +/- 3.3%) than in the medium con taining PVA alone (single-control) (65.2 +/- 7.9%). Adding both HT and <bet a>-ME showed significantly (P < 0.05) higher rates (92.6 +/- 2.7%) of norma l fertilization than did adding Hi alone (63.5 +/- 4.6%). Also, adding both HT and <beta>-ME significantly (P < 0.05) lowered the polyspermy rate than did adding HT alone. Adding either <beta>-ME or both HT and beta -ME showe d no significant difference in cleavage. Blastocyst development did not imp rove significantly adding either HT, beta -ME or both, although beta -ME al one 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 resu lts show that adding beta -ME to a chemically defined maturation medium inc reased the intracellular GSH level of bovine oocytes cultured individually, and can improve the maturation rate leading to the blastocyst stage throug hout in vitro production. (C) 2001 by Elsevier Science Inc.