Oxidative stress during the interaction of gametes

Oxidative stress, commonly defined as a disturbance in the prooxidant and antioxidant levels, may be causatively involved in the etiology of defective sperm function. To mimic the physiological situation, in this study xenogeneic activators of the oxidative burst of sperm were excluded. In addition, transition metal-driven production of reactive oxygen species was avoided by chelation of Fenton catalysts. On average, 28 +/- 4 U of superoxide dismutase (SOD) and 375 +/- 105 mumol/L of sulfhydryls were found in normozoospermic ejaculates from 10 healthy men. The in vitro inhibition of superoxide dismutase by diethyldithiocarbamate caused the rapid oxidation of seminal plasma sulfhydryls, suggesting a pivotal role for SOD in maintaining the antioxidant defense system and protecting against oxidant-induced injury. The production of superoxide by hamster sperm as well as hamster oocytes was examined by lucigenin-mediated chemiluminescence both prior to and following the addition of sperm to oocytes for in vitro fertilization. During fusion, the generation of superoxide from both sperm and oocytes was markedly suppressed. This inhibition was partially due to the superoxide dismutase released during gamete interactions.