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
The NADPH produced via the PPP appears to work at two levels that are finely balanced. Overactivity of this pathway may damage the sperm, whereas underactivity may render the sperm unable to fertilize. Excessive G6PDH activity has been found to be associated with defective sperm function in humans, suggesting that an appropriate regulation of the PPP is important for the fertilizing capacity of sperm. NADPH could activate the glutathione (GSH)-dependent scavenger system to decrease the levels of ROS; however, this system is probably not efficient in human spermatozoa since they contain very low quantities of GSH peroxidase. In the mouse, despite a significant amount of both GSH and GSH peroxidase, the efficiency of this scavenger system is abolished in case of oxidative stress.