The stability of a novel synthetic peptide-type hemostatic material under digestive enzyme.

BACKGROUND: A synthetic peptide 'TDM-623' is a promising hemostatic material for endoscopic surgery in the gastrointestinal tract. However, its stability under gastric/pancreatic secretion has yet to be shown. Hence, this study verified the stability of TDM-623 under digestive enzyme. MATERIAL AND METHODS: TDM-623 (1 mL) was applied to a dish and left at 37 °C for gel formation. Artificial gastric/pancreatic juice and saline were applied to each dish (n = 10). The stability of TDM-623 was evaluated at 0 min-48 h. The evaluation methods were the peptide amount dissolved in the solvent measured by high-performance liquid chromatography and morphological changes revealed by photography and eosin staining, as well as physical changes found by weight. RESULTS: The amount of dissolved peptides originating from the TDM-623 gel after gastric juice exposure was negligible compared to its original amount: a maximum of 10.3% dissolved after 48 h. No significant amounts of dissolved peptides were seen at any timepoint of exposure to pancreatic juice. Also, there were neither morphological nor physical changes after exposure to digestive enzymes for 48 h. CONCLUSION: This study suggests that TDM-623 is sufficiently stable under digestive enzyme. TDM-623 is thus expected to be a durable hemostatic material that protect wound left by endoscopic surgery.

Imipramine N-glucuronidation in human liver microsomes: biphasic kinetics and characterization of UDP-glucuronosyltransferase isoforms.

A method for the direct determination of imipramine N-glucuronidation in human liver microsomes by high-performance liquid chromatography with UV detection was developed. Imipramine was incubated with human liver microsomes and UDP-glucuronic acid. The Eadie-Hofstee plots of imipramine N-glucuronidation in human liver microsomes were biphasic. For the high-affinity component, the K(m) was 97.2 +/- 39.4 microM and the V(max) was 0.29 +/- 0.03 nmol/min/mg of protein. For the low-affinity component, the K(m) was 0.70 +/- 0.29 mM and the V(max) was 0.90 +/- 0.28 nmol/min/mg of protein. The imipramine N-glucuronosyltransferase activities were not detectable in two samples of human jejunum microsomes. Among recombinant UDP-glucuronosyltransferases (UGTs) in baculovirus-infected insect cells (Supersomes or Bacurosomes) or human B-lymphoblastoid cells tested in the present study (UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A7, UGT1A8, UGT1A9, UGT1A10, UGT2B7, and UGT2B15), only UGT1A4 showed imipramine N-glucuronosyltransferase activity. The activity in UGT1A4 Supersomes was higher than that in recombinant UGT1A4 expressed in human B-lymphoblastoid cells at all imipramine concentration tested. The kinetics of imipramine N-glucuronidation in UGT1A4 Supersomes did not fit the Michaelis-Menten plot, showing a K(m) of >1 mM. In contrast, in UGT1A4 expressed in human B-lymphoblastoid cells, K(m) was 0.71 +/- 0.36 mM and the V(max) was 0.11 +/- 0.03 nmol/min/mg of protein. Interindividual differences in the imipramine N-glucuronidation in liver microsomes from 14 humans were at most 2.5-fold. The imipramine N-glucuronosyltransferase activities in 11 human liver microsomes were significantly (r = 0.817, P < 0.005) correlated with the glucuronosyltransferase activities of trifluoperazine, a typical substrate of UGT1A4. This is the first report of the biphasic kinetics of imipramine N-glucuronide in human liver microsomes.