Gastrointestinal absorption of recombinant hirudin-2 in rats.

To investigate the absorption of recombinant hirudin-2 (rHV2) after oral administration to rats and its possible absorption mechanism, a series of experiments were carried out. The degradation of (125)I-rHV2 in the luminal contents and variant mucosal subcellular fractions, as well as the effect of degradation inhibition of some adjuvant was investigated. The bioavailability of rHV2, with or without degradation inhibitor after oral administration to rats was estimated, whereas the in situ loop test and everted sac experiment were also conducted to understand more about the gastrointestinal absorption of rHV2 in rats. It was demonstrated that the rHV2 was not stable in the luminal contents and subfraction of the intestinal mucosa. Some enzyme inhibitor, such as bacitracin or casein, could inhibit the degradation to certain degrees. The intact rHV2 molecules were found in the rat plasma after oral administration, and the bioavailability varies obviously, dependent on the analytical method. Some of the enzyme inhibitor could enhance the rHV2 oral absorption. There is no site difference on rHV2 absorption in different segments of small intestine. The possible transport mechanism of rHV2 across the gastrointestinal tract is concerned with the endocytosis process.