title: Effect of protein synthesis inhibition before or during in vitro maturation on subsequent development of bovine oocytes.
abstract: The overall objective of this study was to assess the effect of maintaining meiotic arrest in bovine oocytes in vitro on developmental competence. In Experiment 1 the effect of inhibition of meiotic resumption using cycloheximide (CX), on subsequent was examined. Immature cumulus oocyte complexes (COCs, n = 804) were cultured in the absence (24 h) or presence of CX for 6, 12, 18 or 24 h. The control was inseminated 24 h later, while CX-treated oocytes were cultured for a further 24 h before insemination. In Experiment 2 the effect of exposing the oocyte (n = 1239) during meiotic arrest to putative stimulatory substances (pFSH and FCS) was examined. In Experiment 3, to study the importance of protein synthesis during maturation, synthesis was blocked for a 6-h period at various times (6, 12, 18 h) after start of culture (n = 1117). In Experiment 1, there was no difference in cleavage rate between treatments. However, the percentage of 5 to 8 cell embryos at 72 h post insemination was significantly lower after CX treatment (64 vs 42 to 51%; P < 0.05). This was reflected in a lower rate of blastocysts at Day 6 (9 to 15 vs 31%, P < 0.002). While the blastocyst rate at Day 8 was lower in CX-treated oocytes, the effect was only significant when CX was present for longer than 12 h. A marked decrease in development was noted following inhibition for 18 h or more compared with the control (17 to 19 vs 40%; P < 0.0002). In Experiment 2, addition of either FSH or FCS to oocytes in the presence of CX had no effect on any of the parameters studied, even though there was a positive effect in control oocytes. In Experiment 3, treatment with CX after the oocytes had matured for varying periods resulted in decreased blastocyst rates at Days 6 and 8 of culture. The most significant drop in development occurred when oocytes were cultured for 12 h before exposure to CX (15 vs 40%; P < 0.0001). In conclusion, CX-blocked oocytes retained their developmental competence, although final blastocyst yields were reduced.
authors.affiliation: INRA-PRMD, Nouzilly, France. lonergan@pop3.ucd.ie
authors.forename: P
authors.initials: P
authors.lastname: Lonergan
authors.forename: T
authors.initials: T
authors.lastname: Fair
authors.forename: H
authors.initials: H
authors.lastname: Khatir
authors.forename: G
authors.initials: G
authors.lastname: Cesaroni
authors.forename: P
authors.initials: P
authors.lastname: Mermillod
mesh_terms: D000818:Animals; D002417:Cattle; D046508:Culture Techniques; D003513:Cycloheximide / Q000494:pharmacology; D005260:Female; D005312:Fetal Blood; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D008540:Meiosis / Q000187:drug effects*; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D014176:Protein Biosynthesis; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology*
chemical_list: D011500:Protein Synthesis Inhibitors; D005640:Follicle Stimulating Hormone; D003513:Cycloheximide