Kinetics of meiotic progression, M-phase promoting factor (MPF) and mitogen-activated protein kinase (MAP kinase) activities during in vitro maturation of porcine and bovine oocytes: species specific differences in the length of the meiotic stages

The kinetics of nuclear maturation, hi-phase promoting factor (MPF) and mit ogen-activated protein kinase (MAP kinase) activities during in vitro matur ation of porcine and bovine oocytes were examined. A further objective was to determine the duration of the meiotic stages during the maturation proce ss. Porcine and bovine cumulus-oocyte complexes (COCs) were incubated in TC M 199 supplemented with 20% (v/v) heat inactivated fetal calf serum (FCS), 0.05 mug/ml gentamycin, 0.02mg/ml insulin, 2.5 mug/ml FSH and 5 mug/ml LH. COCs were removed from the culture media in hourly intervals starting immed iately after recovery from the follicle until 24 (bovine) or 48 h (porcine) of culture. Oocytes were either fixed to evaluate the maturation status or the activity of MPF, assessed by its histone H1 kinase activity, and MAP k inase were determined by a radioactive assay simultaneously. In oocytes of both species, the MPF activity oscillated during the culture period with tw o maxima corresponding with the two metaphases: between 27-32 and after 46 h (porcine) and between 6-9 and after 22h (bovine), There was a temporary d ecline in activity after 33-38 (porcine) and after 19h (bovine), which corr esponded with anaphase I and telophase I. MAP kinase activity increased dur ing the whole culture period and reached maximum levels after 47 (porcine) and after 22 h (bovine), In porcine oocytes, the h;IAP kinase was activated before GVBD and MPF activation. In bovine oocytes, MPF and MAP kinase were activated at approximately the same time as the GVBD (8-9 h of incubation) . In average porcine, oocytes remain 23.4 h in the germinal vesicle (GV) st age (13 h in GV I, 5.7 h in GV II, 3.2 h in GV III and 1.5 h in GV IV), 0.9 h in diakinese, 9,6 h in the metaphase I, 2.8 h in anaphase I and 1.9 h in telophase I of the first meiotic division. In bovine oocytes, the temporal distribution of the meiotic stages were 8.5 h for the GV stage, 1.2 h for diakinese, 8.3 h for metaphase I, 1.6 h for anaphase I and 1.9 h for teloph ase I. These results indicate that the duration of the meiotic stages diffe rs between the species and that MAP kinase is activated before MPF and GVBD in porcine oocytes. (C) 2001 Elsevier Science B.V. All rights reserved.