Currently, the attention of many researchers is drawn to determine the features of the regeneration of the mucous membrane of the gastrointestinal tract in ulcers, as one of the most important protective factors in this pathology. Purpose - to investigate the indicators of endogenous polypeptides (epidermal growth factor - EGF and transforming growth factor α-TGF-α) in the serum of children with duodenal ulcers. Materials and methods. The study included 56 children aged 7-18 years (36 children with duodenal ulcer - the main group and 20 healthy children (comparison group). The content of endogenous polypeptides in serum was determined by enzyme-linked immunosorbent assay (ELISA) using the Human EGF ELISA Kit (Invitrogen, USA) for EGF and R&D system (USA) for TGF-α according to the manufacturer’s instructions. Statistical processing of the obtained results was carried out using parametric and non-parametric methods of evaluation of the obtained results. Results. Slightly higher levels of EGF and TGF-α were found in boys of both subgroups of the main group (EGF: 561.45 [391.81-699.34] pg/ml and 544.67 [411.23-569.77] pg/ml, p>0.05; TGF-α: 47.91 [21.41-29.69] and 42.56 [35.45-49.21] pg/ml, p>0.05). Concentrations of endogenous factors in exacerbation of ulcerative process are higher than in remission (p<0.001) and in remission does not reach that in healthy children, p<0.01). In patients with severe duodenal ulcers, EGF and TGF-α concentrations are higher (p<0.01), which may be due to the maximum degree of inflammatory-destructive process. Conclusions. The course of duodenal ulcer leads to disorders in the regulation of proliferative processes in the mucous membrane, which is manifested by increased levels of EGF and TGF-α in the serum of sick children, the more severe the course, the higher process. The research was carried out in accordance with the principles of the Helsinki declaration. The study protocol was approved by the Local ethics committee of the participating institution. The informed consent of the patient was obtained for conducting the studies. No conflict of interest was declared by the authors. Key words: children, duodenal ulcer, epidermal growth factor (EGF), transforming growth factor α (TGF-α).

Various gastrointestinal and extragastrointestinal diseases are associated with H. pylori in children and adolescents, but the strongest recommendations for testing and treatment are made only in children and adolescents with duodenal ulcer (DU). The inability of natural immune mechanisms to recognize and eliminate H. pylori leads to the development of acute inflammation. The most promising developments so far are studies of the antibacterial effect of endogenous antimicrobial peptides (AP), among which defensines 1-3 (human neutrophil peptides, HNPs 1-3) and cathelicidins (LL-37) are the most important for the human body. Purpose - to investigate the concentration of HNPs 1-3 and LL-37 in the blood of children with DU in order to determine the activity of the inflammatory process of the mucous membrane. Materials and methods. 65 children aged 7-18 years, suffering from DU and 25 healthy children of the corresponding age (comparison group) were examined. The level of HNPs 1-3 and LL-37 was determined in blood plasma by enzyme-linked immunosorbent assay according to the manufacturers instructions. Results. Patients were divided by age, sex, location and size of the ulcer, presence of the H. pylori bacterium. A toxigenic strain of H. pylori was detected in 80.9% of examined children, and the level of HNPs 1-3 in blood plasma was 3 times higher and the level of LL-37 was 2.5 times higher in children with H. pylori-associated DU than in healthy children (p=0.01). Concentrations of HNPs 1-3 and LL-37 in blood plasma were higher in patients with an active inflammatory process in the mucous membrane and were positively correlated with the degree of inflammation activity (r=0.67, p=0.05 and r=0.69, p=0.01). After eradication therapy, AP levels decrease, while the degree of decrease directly depends on the activity of the inflammatory process. Conclusions. Probably higher concentrations of HNPs 1-3 and LL-37 were found in the blood plasma of children with H. pylori-associated DU. Considering the direct correlations between the levels of HNPs 1-3 and LL-37 and the degree of activity of the inflammatory process, these indicators can be used as biomarkers of the adverse course of H. pylori-associated DU. The research was carried out in accordance with the principles of the Helsinki Declaration. The study protocol was approved by the Local Ethics Committee of all participating institutions. The informed consent of the patient was obtained for conducting the studies. No conflict of interests was declared by the authors.