Category Archives: Spermatozoa

A Possible Role for the Pentose Phosphate Pathway: DISCUSSION(7)

Alternatively, NADPH has been postulated to be a cofactor for a putative NADPH oxidase that would be responsible for the production of ROS in human sperm. One of these ROS, H2O2, exerts a physiological function in controlling the levels of protein tyrosine phosphorylation. In the mouse, the phosphorylation of tyrosine residues is important for sperm functions such as capacitation and acrosome reaction. In addition, glucose … Continue reading

A Possible Role for the Pentose Phosphate Pathway: DISCUSSION(6)

An intracellular effect of exogenously added NADPH would be consistent with intracellular production of NADPH by the PPP. In the case of an extracellular effect of NADPH, it may be speculated that the reduction of NADP to NADPH by glucose 6-phosphate dehydrogenase and 6-phospho-gluconate dehydrogenase takes place at the membrane level and that NADPH is released at the external face of the plasma membrane. Cheap Diskus Advair

A Possible Role for the Pentose Phosphate Pathway: DISCUSSION(5)

The inhibitory effect of cytochalasin B has been interpreted as the result of its inhibition of glucose uptake and the consequent decrease in PPP activity. The influence of a cyto-skeletal destabilization of the spermatozoa by a long exposure to cytochalasin B cannot be totally excluded. Maro et al., however, have shown that in vitro fertilization of mouse cumulus-enclosed oocytes was not affected by cytochalasin D, … Continue reading

A Possible Role for the Pentose Phosphate Pathway: DISCUSSION(4)

As demonstrated previously, glucose must be metabolized to exert its positive effect on fusion. Although glycolysis is important for sperm functions such as hyperactivated motility, this metabolic pathway does not appear to be responsible for successful gamete fusion since its inhibition by phloretin or by iodoacetate (inhibitor of the glycolytic enzyme glyceraldehyde phosphate dehydrogenase ) in capacitated spermatozoa before insemination of zona-free oocytes and during … Continue reading

A Possible Role for the Pentose Phosphate Pathway: DISCUSSION(3)

As in rats and humans, we have shown the presence of the high-affinity glucose transporter GLUT3 in mouse sperm, indicating the immense need of sperm for glucose. Interestingly, the presence of cytochalasin B but not phloretin inhibited the PPP activity, although both are able to bind to facilitative glucose transporters (GLUT1, GLUT3) and to inhibit glucose uptake by sperm in different species. Cytochalasin B has … Continue reading

A Possible Role for the Pentose Phosphate Pathway: DISCUSSION(2)

However, evaluation of the PPP by using the ratios of 14CO2 produced from [1-14C]glucose and [6-14C]glucose is not appropriate, and the absence of a difference in yields of 14CO2 does not prove that the PPP is absent or inactive. 14CO2 can be released from [1-14C]glucose by metabolism through the PPP or in the Krebs cycle after glycolytic metabolism to [3-14C]pyruvate. In the presence of unlabeled … Continue reading

A Possible Role for the Pentose Phosphate Pathway: DISCUSSION(1)

In this study, we have presented data that further characterize the glucose metabolism of mouse spermatozoa and emphasize its importance in fertilization. We have shown 1) that mouse epididymal spermatozoa have a functional PPP, and 2) that NADPH can substitute for glucose in gamete fusion. These results strongly indicate that sperm need to generate NADPH via the PPP in order to achieve fertilization. ampicillin antibiotic

A Possible Role for the Pentose Phosphate Pathway: RESULTS(2)

Glucose metabolism was measured in the presence of phloretin and cytochalasin B (Fig. 3), which are inhibitors of facilitative glucose transport. Blocking glucose uptake by 50 ^M cytochalasin B induced an inhibition of both glycolysis and PPP activity by 36% and 46%, respectively. The PPP activity was diminished by 80% in the presence of 200 ^M cytochalasin B (data not shown). In contrast, 0.5 mM … Continue reading

A Possible Role for the Pentose Phosphate Pathway: RESULTS(1)

Glucose Metabolism of Capacitated Spermatozoa In a first series of experiments, identification of the glucose transporter and metabolic studies were undertaken in a population of capacitated sperm. Using Western blot analysis (Fig. 1), we found that a band migrating at 45 kDa was recognized by anti-GLUT3, indicating that this transporter was expressed in mouse spermatozoa. Mouse sperm proteins did not react with anti-GLUT1, but mouse … Continue reading

A Possible Role for the Pentose Phosphate Pathway: MATERIALS AND METHODS(6)

Immunoblotting Western analysis was performed using procedures similar to those described for the detection of GLUT in preimplantation embryos by Aghayan et al.. Briefly, 0.25 X 106 spermatozoa or 30 mouse blastocysts were lysed in 10 ^l of lysis buffer and stored at-20°C. Before electrophoresis, the samples were diluted in a double-strength solution of Laemmli’s sample buffer. Electrophoresis was performed under reducing conditions using a … Continue reading