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, which is a more efficient inhibitor of the cytoskeleton than cytochalasin B and does not interfere with glucose transport across the plasma membrane. The results of Maro et al., points 1 and 2 above, and the observation that spermatozoa pretreated for 30 min with cytochalasin B did not alter penetration rate into the oocytes indicate that a cytoskeletal effect was most likely not responsible for our observation. In the event that cytochalasin B does not acting via destabilization of cytoskeletal elements, we can speculate that its role as an inhibitor of glucose uptake and PPP activity was responsible. ventolin 100 mcg
In this context, the observation that exogenously added NADPH can support gamete fusion in the absence of glucose is particularly relevant to the implication of the PPP in the fusing capacity of the sperm. Exogenous addition of NADPH to human spermatozoa has been shown to induce reactive oxygen species (ROS) and tyrosine protein phosphorylation. Although NAdPh has limited membrane permeability, the diffusion of a small proportion of the molecules through the plasma membrane has been suggested.