Resumption of meiosis in pig oocytes cultured with cumulus and parietal granulosa cells: The effect of protein synthesis inhibition

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Abstract
In denuded and cumulus‐enclosed pig oocytes, puromycin at concentrations 5, 10, and 25 μg/ml did not lower the rate of germinal vesicle breakdown (GVBD) after 24 h of culture. GVBD was prevented in 50, 75, and 100 μg/ml of puromycin. After 40 h of culture, 5 and 10 μg puromycin/ml impaired significantly incidence of metaphase II (42 and 30%), respectively. Concetrations of 25 and 50 μg puromycin/ml absolutely prevented the first polar body (I PB) expulsion. The results indicated that GVBD in pig oocytes is far less sensitive to puromycin than I PB expulsion. Culture of cumulus‐enclosed pig oocytes isolated with a piece of membrana granulosa (C+P oocytes) did not allow GVBD after 24 and 32 h in control medium. After 24 h of culture, GVBD occurred in 43 and 56% of C + P oocytes in the medium supplemented with 17 and 25 μg puromycin/ml. GV was broken down in 80 and 68% of C + P oocytes cultured in 17 and 25 μg puromycin/ml for 32 h. It is concluded that inhibition of protein synthesis by puromycin released pig oocytes from the block exerted by granulosa cells.