BACKGROUND: Endometriosis is known to be linked with altered activities of antioxidant enzymes and with their gene polymorphisms. Progestins are known to induce glutathione peroxidase activity in the endometrium and promote reduction of endometrial lesions. It could be useful to estimate the correlation between the activity of glutathione peroxidase within endometrial lesions and their degree of reduction. AIM: The present study was aimed at estimating glutathione peroxidase activity in surgically induced endometrial-like lesions of different degree of reduction in rat model of endometriosis. MATERIALS AND METHODS: The method for determining glutathione peroxidase activity using hydrogen peroxide as a substrate and 5,5-dithiobis(2-nitrobenzoic acid) for estimation of residual reduced glutathione was applied for quantitative analysis of the enzyme activity in endometriotic foci, surgically induced in female Wistar rats. An assay of glutathione peroxidase activity in tissue homogenates was performed at 37C in a reaction medium containing Tris-HCl buffer supplemented with tetrasodium ethylenediaminetetraacetate and sodium azide (pH 8.5) in the presence of 0.55 mM reduced glutathione and 0.192 mM hydrogen peroxide. Before adding trichloroacetic acid, 40-second incubation was used. The correlation between the specific activity of the enzyme and protein amount in endometriotic foci was estimated. RESULTS: In a rat model of endometriosis, there was a high, well-determined glutathione peroxidase activity in endometriotic foci. For the same endometriotic tissue sample, the enzymatic activity was proportional to the amount of protein in the reaction mixture. The range of specific glutathione peroxidase activity was 2.436.45 micromoles of consumed glutathione per minute per milligram of protein (n = 7). In most reduced endometriotic foci (with the minimum amount of endometriotic tissue), the highest specific activity of glutathione peroxidase was found (the Spearmans rho of 0.93 with p = 0.0067). CONCLUSIONS: The method for determining glutathione peroxidase activity using hydrogen peroxide and 5,5-dithiobis(2-nitrobenzoic acid) is convenient for working with the endometriotic tissue in a rat model of endometriosis. We can accept, with p 0.01, that weight of endometriotic foci is negatively linked with specific glutathione peroxidase activity within their tissue. The results are analogous to the previously obtained data on catalase activity and suggest the involvement of both antioxidant enzymes in reduction of endometrial lesions.

Hypothesis/aims of study. There is a link between the activities (and polymorphisms of genes) of antioxidant enzymes and endometriosis. It is also known that progesterone induces some antioxidant enzymes in the endometrium and that progesterone analogs are effective for reduction of endometrial lesions. In addition to morphometric and histological estimations of endometriosis regression, it could be useful to assess the activity of antioxidant enzymes within endometriotic foci. The present study is aimed at estimating the activity of catalase, a hydrogen peroxide-detoxifying enzyme, in surgically induced endometrial-like lesions with a variable degree of reduction. Study design, materials and methods. The study was carried out on 12 mature female rats of Wistar strain. Endometrial-like lesions were induced by autotransplantation of uterine tissue fragments on the abdominal wall. After 35-37 days, the endometrial foci were extracted. Catalase activity in the ectopic endometrium was determined by the Beers Sizer method modified as follows: recording hydrogen peroxide concentration decrease at 250 nm and using 3-amino-1,2,4-triazole (AT) to assess specificity. The correlation between the specific catalase activity and protein amount in the ectopic endometrium was estimated. Results. At the wavelength of 250 nm, a relatively weak interference of AT with other components of the reaction mixture was observed, which allows using the specific catalase inhibitor to indicate the enzyme activity. The activity is measured in a short period of incubation (less than 1 minute) and is proportional to amount of the endometrial tissue extract in the reaction mixture. As a rule, the most reduced endometriotic foci (with the lowest weight) possessed a higher catalase activity (the Spearmans rho was 0.66 with p 0.025). Conclusion. The method for determining catalase activity was adapted to work with endometriotic foci. With p 0.025, we can accept that a low weight of endometriotic foci is linked with a relatively high catalase activity within their tissue. The results allow suggesting the involvement of catalase in reduction of endometrial lesions.

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