Meiotic progression, mitochondrial features and fertilisation characteristics of porcine oocytes with different G6PDH activities

• Published in: Reproduction fertility and development Vol. 22; no. 5; pp. 830 - 838
• Main Authors: Egerszegi, István, Alm, Hannelore, Rátky, József, Heleil, Bassiouni, Brüssow, Klaus-Peter, Torner, Helmut
• Format: Journal Article
• Language: English
• Published: Australia Collingwood, Victoria: CSIRO Publishing 2010
• Subjects: Animals; Cell Nucleus - physiology; Chromatin - ultrastructure; Coloring Agents; Cytoplasm - ultrastructure; Female; Fertilization in Vitro - veterinary; Glucosephosphate Dehydrogenase - metabolism; Meiosis; Microscopy, Fluorescence; mitochondria; Mitochondria - physiology; Mitochondria - ultrastructure; Oocytes - enzymology; Oocytes - physiology; Oocytes - ultrastructure; Oxazines; Swine
• ISSN: 1031-3613
• DOI: 10.1071/RD09140

The aim of the present study was to investigate the developmental competence, mitochondrial characteristics and chromatin status of immature follicular porcine oocytes selected for their glucose-6-phosphate dehydrogenase (G6PDH) activity by brilliant cresyl blue (BCB) staining. In Experiment 1, the oocyte parameters were determined in parallel right after BCB staining (T₀), after 22 h of in vitro maturation (IVM) (T₂₂) and after 44 h of IVM (T₄₄) (n = 496). BCB-stained oocytes (BCB+) at T₀ were characterised by fibrillated chromatin filaments in their germinal vesicles (GV) and diakinesis stages whereas unstained (BCB-) oocytes at T₀ contained in their GV mainly condensed stages of chromatin (P < 0.05). After 22 h of IVM BCB+ oocytes showed a prominent chromatin configuration of metaphase I and after 44 h the majority developed a M II nuclear configuration in contrast to the BCB- group (P < 0.0001). Differences were also observed between the two oocyte populations in their mitochondrial activity (P < 0.05). At the beginning of IVM BCB+ oocytes were characterised by high mitochondrial activity in their cytoplasm. The BCB+ oocytes showed clear visible homogenous distributions of mitochondria (P < 0.005) and contained more aggregated clusters of mitochondria in contrast to BCB- oocytes (P < 0.005). In Experiment 2, 318 oocytes were tested for their G6PDH activity and introduced to IVM and IVF. Only oocytes from the BCB+ group, which were matured after 44 h up to the stage of M II (81.6%) were fertilised (17.4%), penetrated (46%) or activated (15.6%) after IVF. These results indicate a relationship between the G6PDH activity of porcine oocytes before IVM and their subsequent nuclear development, mitochondrial activity and aggregation.