[Importance of free radicals during the reproduction cycle]

The peroxidation products, the free radicals, and the antioxidants compounds notable increase during ovulation, implantation, and pregnancy evolution. Superoxide anion (O2-) rise six time more on the proestrous, than on other stages, while its regulation enzyme, the superoxide dismutase (SOD), decreases. The presence of superoxide anion is related with the edema and the cellular proliferation on the estrous. Superoxide anion is also connected with the increase of fluidity and polarity of the membranes during the implantation. As the pregnancy elapse the lipoperoxides products and the antioxidant compounds augment suggesting that lipoperoxides evoke defense mechanism in a way that, at the end of the pregnancy, the antioxidants exceed peroxidative phenomena. By the other hand, the nitric oxide radical has gained great importance during the pregnancy because it is considered one of the most powerful relaxants of smooth muscle. The inhibition of its synthesis provokes similar signs to the preeclampsia and tis administration can revert many vascular alterations. The role of free radicals is not limited to dangerous effects, but it also, in adequate concentrations, includes the as stimulators of grown factors, and participants of the membranes fluidity.