ROLE OF GERMINAL VESICLE ON PROTEIN-SYNTHESIS IN RAT OOCYTE DURING IN-VITRO MATURATION

To investigate the role of the germinal vesicle (GV) on in vitro matur ation (IVM) of rat oocytes, we examined protein synthesis during IVM b y comparing polypeptide patterns in control and enucleated oocytes usi ng one and two-dimensional sodium dodecyl sulfate-polyacrylamide gel e lectrophoresis (SDS-PAGE). Separation of polypeptides extracted from t he cytoplasm of GV by one-dimensional SDS-PAGE revealed that a 55 kDa polypeptide was present only in the GVs of rat oocytes. At 0, 12, 24, 36, and 44 hr after PMSG injection, prior to the initiation of maturat ion, enucleated oocytes synthesized the same major polypeptides as cum ulus intact (CI) oocytes. During meiotic maturation, no major changes were detected in protein synthesis from prophase (GV stage) to prometa phase 1 (0-6 hr IVM). However, after entry into prometaphase 1 (7 hr I VM), striking changes were seen; a 24 kDa polypeptide disappeared and expression of a 34 kDa polypeptide became stronger. This pattern laste d until metaphase II. We detected no major differences in the pattern of protein synthesis between CI and enucleated oocytes using two-dimen sional PAGE. These results indicate that protein synthesis in the matu ring rat oocyte is controlled by cytoplasmic regulators rather than in trinsic nuclear components. (C) 1996 Wiley-Liss, Inc.