In order to explore this hypothesis, the potential consequences of hypoxia and inflammation (alone or in association) on citrulline synthesis by the OCT in human enterocytes will be determined, thanks to an "explant" culture model of duodenal tissue. Duodenal biopsies will be removed during oesophago-gastro-duodenoscopies performed in the Hepato-gastro-enterology unit of Grenoble University Hospital, among patients expected to undergo a gastroscopy for any diagnostic purpose. 30 patients will be selected during a period of 6 months. After complete information and written agreement, 8 biopsy specimens will be removed from the duodenum of each patient and processed for organ culture.