RESUMO
The aim of this work was to study the regulation of PFK 1 and G6PDH, two key enzymes involved in glucose metabolism in cumulus oocyte-complexes (COCs), and its relationship with the oocyte maturation process. It was observed that the activity of PFK 1 in the presence of ATP was inhibited whereas the addition of AMP increased the activity (P < 0.05). To verify the effect of the physiological modulators on the COC glycolytic pathway, the lactate production during IVM and the maturation rate were evaluated. In accordance with the enzymatic activity, the glycolytic activity evaluated by lactate production and the maturation rate diminished (P < 0.05) with the addition of ATP. While the AMP had a dose response effect on the lactate production, the maturation rate remained unaltered. It was observed that NADPH inhibited the activity of the G6PDH and the addition of NADP increased the activity of the enzyme (P < 0.05). To verify the effect of the physiological modulators on the COC pentose phosphate pathway (PPP), the proportion of colourless oocytes evaluated by brilliant cresyl blue (BCB) and the maturation rate were carried out. In presence of NADPH an inhibition (P < 0.05) on PPP and maturation rate was observed. On the other hand, NADP had no effect on PPP activity and maturation rate. The present study shows that the regulation of key enzymes of glucose metabolism in bovine COCs are regulated mainly by the energetic charge and the redox status. We also reported a tight relation between the activity of the PFK 1 and G6PDH enzymes, glycolytic and PPP activities and the oocyte maturation process.
Assuntos
Animais , Bovinos , Bovinos/metabolismo , Fosfofrutoquinase-1 , Glucosefosfato DesidrogenaseRESUMO
The aim of this work was to study the regulation of PFK 1 and G6PDH, two key enzymes involved in glucose metabolism in cumulus oocyte-complexes (COCs), and its relationship with the oocyte maturation process. It was observed that the activity of PFK 1 in the presence of ATP was inhibited whereas the addition of AMP increased the activity (P < 0.05). To verify the effect of the physiological modulators on the COC glycolytic pathway, the lactate production during IVM and the maturation rate were evaluated. In accordance with the enzymatic activity, the glycolytic activity evaluated by lactate production and the maturation rate diminished (P < 0.05) with the addition of ATP. While the AMP had a dose response effect on the lactate production, the maturation rate remained unaltered. It was observed that NADPH inhibited the activity of the G6PDH and the addition of NADP increased the activity of the enzyme (P < 0.05). To verify the effect of the physiological modulators on the COC pentose phosphate pathway (PPP), the proportion of colourless oocytes evaluated by brilliant cresyl blue (BCB) and the maturation rate were carried out. In presence of NADPH an inhibition (P < 0.05) on PPP and maturation rate was observed. On the other hand, NADP had no effect on PPP activity and maturation rate. The present study shows that the regulation of key enzymes of glucose metabolism in bovine COCs are regulated mainly by the energetic charge and the redox status. We also reported a tight relation between the activity of the PFK 1 and G6PDH enzymes, glycolytic and PPP activities and the oocyte maturation process.(AU)
Assuntos
Animais , Bovinos , Bovinos/metabolismo , Fosfofrutoquinase-1 , Glucosefosfato DesidrogenaseRESUMO
Porcine immature oocyte quality (i.e., that of live oocytes at the germinal vesicle stage) was evaluated according to features of the surrounding cumulus, aiming to establish maturational competence of different subpopulations of such cumulus-oocyte complexes. Six subpopulations were identified: A1 (with a dense cumulus), A2 (with a translucent cumulus), B1 (with the corona radiata), B2 (partly naked oocytes), C (naked oocytes), D (with a dark cumulus). The percent incidence of live oocyte in these subpopulations changed significantly as related to cumulus features, however the occurrence of oocytes in the germinal vesicle stage was lower in class D only. Similar metaphase II rates achieved in A1, A2, B1 and B2 classes after in vitro maturation suggest that the nucleus may in fact mature in vitro, in spite of the different accompanying cumulus features which are typical of these classes. In contrast, a higher cytoplasmic maturation rate obtained in class A may indicate a stronger dependence of this variable upon cumulus features than that shown by nuclear maturation. When different types of cumulus expansion after in vitro maturation were considered (i.e., fully expanded cumulus, partly expanded cumulus, and partly naked oocyte), no differences were found in the percent of oocytes reaching metaphase II or cytoplasmic maturation. It is concluded that morphological features of the collected porcine cumulus-oocyte complexes (rather than cumulus behavior during culture) may be useful for selection of potentially competent oocytes for in vitro fertilization and embryo production.
Assuntos
Animais , Feminino , Fertilização in vitro , Folículo Ovariano/citologia , Metáfase/fisiologia , Oócitos/citologia , Suínos/fisiologiaRESUMO
Porcine immature oocyte quality (i.e., that of live oocytes at the germinal vesicle stage) was evaluated according to features of the surrounding cumulus, aiming to establish maturational competence of different subpopulations of such cumulus-oocyte complexes. Six subpopulations were identified: A1 (with a dense cumulus), A2 (with a translucent cumulus), B1 (with the corona radiata), B2 (partly naked oocytes), C (naked oocytes), D (with a dark cumulus). The percent incidence of live oocyte in these subpopulations changed significantly as related to cumulus features, however the occurrence of oocytes in the germinal vesicle stage was lower in class D only. Similar metaphase II rates achieved in A1, A2, B1 and B2 classes after in vitro maturation suggest that the nucleus may in fact mature in vitro, in spite of the different accompanying cumulus features which are typical of these classes. In contrast, a higher cytoplasmic maturation rate obtained in class A may indicate a stronger dependence of this variable upon cumulus features than that shown by nuclear maturation. When different types of cumulus expansion after in vitro maturation were considered (i.e., fully expanded cumulus, partly expanded cumulus, and partly naked oocyte), no differences were found in the percent of oocytes reaching metaphase II or cytoplasmic maturation. It is concluded that morphological features of the collected porcine cumulus-oocyte complexes (rather than cumulus behavior during culture) may be useful for selection of potentially competent oocytes for in vitro fertilization and embryo production.(AU)
Assuntos
Animais , Feminino , Fertilização in vitro , Metáfase/fisiologia , Oócitos/citologia , Folículo Ovariano/citologia , Suínos/fisiologiaRESUMO
Porcine immature oocyte quality (i.e., that of live oocytes at the germinal vesicle stage) was evaluated according to features of the surrounding cumulus, aiming to establish maturational competence of different subpopulations of such cumulus-oocyte complexes. Six subpopulations were identified: A1 (with a dense cumulus), A2 (with a translucent cumulus), B1 (with the corona radiata), B2 (partly naked oocytes), C (naked oocytes), D (with a dark cumulus). The percent incidence of live oocyte in these subpopulations changed significantly as related to cumulus features, however the occurrence of oocytes in the germinal vesicle stage was lower in class D only. Similar metaphase II rates achieved in A1, A2, B1 and B2 classes after in vitro maturation suggest that the nucleus may in fact mature in vitro, in spite of the different accompanying cumulus features which are typical of these classes. In contrast, a higher cytoplasmic maturation rate obtained in class A may indicate a stronger dependence of this variable upon cumulus features than that shown by nuclear maturation. When different types of cumulus expansion after in vitro maturation were considered (i.e., fully expanded cumulus, partly expanded cumulus, and partly naked oocyte), no differences were found in the percent of oocytes reaching metaphase II or cytoplasmic maturation. It is concluded that morphological features of the collected porcine cumulus-oocyte complexes (rather than cumulus behavior during culture) may be useful for selection of potentially competent oocytes for in vitro fertilization and embryo production.