Compared to male mitochondria, those of females have higher levels of superoxide dismutase, glutathione peroxidase and reduced glutathione due to estrogen-mediated expression of the antioxidant enzymes. Thus, female mitochondria are better protected against adverse effects of reactive oxygen species. A number of studies found differences of baseline oxidative status/ oxidative stress in males and females. Ide et al. reported significantly higher levels of malonic dialdehyde and higher excretion of a marker of lipid peroxidation urinary 8-isoprostaglandin F2a in healthy young men compared to age-matched women. Catalase is one of the three most important antioxidant enzymes, the other two being superoxide dismutase and glutathione peroxidase. It mediates detoxification of endogenous hydrogen peroxide. Augmented catalase expression may possibly correlate with life span and improves the ability of mitochondria to synthesize ATP. In the present study, we observed a highly significant rise of catalase activity in whole saliva of young people upon exposure to an acute psychosocial stressor. We did not find baseline difference between men and women in catalase levels in saliva. Likewise, no significant sex-specific differences in levels of total SOD and catalase in blood plasma and in erythrocytes were found in a study of 860 men and 922 women. Consistently, Ide et al. reported no difference in activity of the enzymes in blood plasma of men and women. Thus, baseline antioxidant activity in women does not differ from that in men. However, we demonstrated that stress-induced increase of catalase activity in saliva is much greater in women than in men and is related to reduced oxidative damage. The underlying molecular mechanisms that augment catalase activity in women are unknown. Similarly, there is no unified concept of possible sources of catalase in saliva. A study by Nickerson et al. in 1957 presumed that catalase origin in stimulated saliva was bacterial, while an earlier report by Eggers-Lura claimed, that catalase was present in the parotid gland secretion. To the best of our knowledge, no other findings have provided a conclusive proof of any of the notions by the present moment. However, several studies investigated catalase activity in saliva. A significant increase in activity of catalase, superoxide dismutase and peroxidase was found in saliva of young women after one month course of aerobic training, while decreased activity of the three antioxidant enzymes was reported in vegetarians. We believe that salivary catalase in women is a part of intrinsic antioxidant defense. An argument in favor of the hypothesis is the fact that all subjects of our study reported good oral health and oral hygiene, and it is therefore highly unlikely that impaired Carfilzomib hygienic habits at stressful circumstances could bring about increased catalase activity from bacteria in women but not in men. One of common measures of oxidative stress is the amount of the end products of lipid peroxidation. The TBARS assay collectively measures lipid peroxidation products, of which malondialdehyde is the most abundant constituent.