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Embryo development, oocyte morphology, and kinetics of meiotic maturation in bovine oocytes exposed to 6‐dimethylaminopurine prior to in vitro maturation
Author(s) -
Avery Birthe,
HaySchmidt Anders,
Hyttel Poul,
Greve Torben
Publication year - 1998
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/(sici)1098-2795(199807)50:3<334::aid-mrd10>3.0.co;2-4
Subject(s) - biology , oocyte , meiosis , microbiology and biotechnology , embryo , embryogenesis , in vitro , andrology , in vitro maturation , oocyte activation , genetics , gene , medicine
The developmental competence of bovine follicular oocytes that had been meiotically arrested with the phosphokinase inhibitor 6‐dimethylaminopurine (6‐DMAP) was studied. After 24 h in vitro culture with 2 mM 6‐DMAP, 85 ± 12% of the oocytes were at the germinal vesicle stage compared to 97 ± 3% at the start of culture ( P > 0.05). After release of the 6‐DMAP inhibition, followed by 24 h IVM, 82 ± 18% were at MII stage, compared with 93 ± 7% in the control group ( P > 0.05). The 6‐DMAP oocytes displayed a much higher frequency of abnormal MII configurations than the control oocytes (67% vs 23%; P < 0.0001). In addition spontaneous oocyte activation was more frequent than among control oocytes (5% vs 0.3%; P 0.0006). After IVF of 6‐DMAP oocytes, normal fertilization was lower (76 ± 8% vs 89 ± 7%; P < 0.01), oocyte activation higher (11 ± 5% vs 2 ± 2%; P < 0.01), and polyspermy slightly but not significantly higher (8 ± 7% vs 4 ± 4%; P > 0.05), compared with the control group. Cleavage was lower (61 ± 13% vs 81 ± 6%; P < 0.001), as well as day 8 blastocyst formation (17 ± 7% vs 36 ± 8%; P < 0.001). The MII kinetics was different for 6‐DMAP and control oocytes. Maximum MII levels were reached at 22 h IVM in both groups, but 50% MII was reached at 17 h in 6‐DMAP oocytes, compared to 20 h in control oocytes. Ultrastructure of MII oocytes was similar in the two groups, but in 6‐DMAP oocytes the ooplasmic vesicle pattern at GV was at a more advanced stage than in control oocytes. In conclusion, 6‐DMAP exposure of GV oocytes prior to IVM induce asynchronous cytoplasmic maturation, leading to aberrant MII kinetics. Thus, at the time of insemination a smaller cohort of oocytes will be at the optimal stage for normal fertilization and subsequent blastocyst development. Mol. Reprod. Dev. 50:334–344, 1998. © 1998 Wiley‐Liss, Inc.