Abstract: AimTo investigate the absorption and distribution of recombinant hirudin-2 (rHV2) in the GI tract in rats after oral administration. MethodsUsing HPLC, fluorescence spectrophotometry and confocal laser scanning microscopy to measure the amount of intact rHV2 absorbed into gastrointestinal mucosa and blood. ResultsHPLC spectrum showed that there were intact rHV2 molecules in plasma after 1 h of oral administration. After oral administration for 3 h, 1.2%-26.8% of fluorescence was found in the GI tract in rats. Chromatographic analysis showed that 2.27%-38.75% of fluorescence recovered from the GI tract luminal contents and mucosa was eluted at the void volume of a Sephadex G-25 column. Microscopic examination showed that FITC-rHV2 was taken up throughout the whole small intestine but the ileum appeared to be a preferred site for FITC-rHV2 transport in rats. ConclusionrHV2 may partially survive in the GI lumen and subsequently absorbed in active form by gastrointestinal tract.