Changes in protein synthesis during maturation of sheep oocytes in vivo and in vitro

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Abstract
The qualitative profiles of the proteins synthesized by sheep oocytes at various stages of maturation were determined by electrophoretic separation in 1 dimension on polyacrylamide SDS [sodium dodecyl sulfate] gels. No change in protein synthetic pattern was observed in oocytes removed before or up to 6 h after the release of LH [luteinizing hormone] in vivo. By 9 h intermediate changes had taken place in at least 12 separate protein bands. Marked alterations in the synthesis of some proteins were apparent 15 h after LH; formation of proteins in 5 of the original bands was either reduced or not detectable, while new synthesis was evident from the appearance of 7 additional bands. The pattern of proteins produced by oocytes cultured within the follicle corresponded closely with that observed in vivo: changes in synthesis were initiated about 9 h after addition of gonadotrophin and were completed by 15 h. Oocytes cultured outside the follicle in a gonadotrophin-containing medium did not exhibit a change in protein synthesis, and at 15 h only those proteins produced during the early stages of maturation were being synthesized.