Résumé
Aim To study the biotransformation of gly-cyrrhizin in rat intestine-liver. Methods The in situ vascularly perfused rat intestine-liver model was estab-lished with a validated LC-MS/MS method for assay of the model perfusate glycyrrhizin and glycyrrhetinic acid. Results The steady state intestinal and liver ex-traction ratios in the once-through perfused rat intes-tine-liver model for glycyrrhizin were ( 4. 2 ± 0. 6 )%and (28. 0 ± 3. 0)%, respectively; the first-order ab-sorption rate constant for glycyrrhizin in the recircula-tion of perfusate to the intestine model was ( 0. 33 ± 0. 06 ) min-1;after intraduodenal administration of gly-cyrrhizin,the main active metabolite in was the perfu-sate glycyrrhetinic acid, which was also found in intes-tinal luminal fluids. Conclusions The first-pass effi-cacy of glycyrrhizin is obvious and there is only a small amount of metabolite in the intestinal mucosa cells;gly-cyrrhizin is metabolized by gut bacteria or liver cells af-ter oral administration;the in situ vascularly perfused rat intestine-liver model can be used in glycyrrhizin pharmacokinetic studies.
Résumé
The antispasmodic effects of acqueous extracts (AE) and tinctures (T) of Aloysia polystachya (Griseb.) Moldenke and Aloysia gratissima (Gillies & Hook.) Tronc., Verbenaceae, were studied on rat isolated ileum and duodenum. These plants are used for gastrointestinal disorders and as eupeptic in South America. Both AE non-competitively inhibited the dose-response curves (DRC) of ACh and the DRC of Ca2+ in high-[K+]o, as well as the T. The T of A. polystachya and A. gratissima respectively inhibited the ACh-DRC at the IC50 of 3.15±0.57 and 6.46±2.28 mg leaves/mL. The Ca2+- antagonist activity of both T occurred with IC50 respectively similar to those of the ACh-DRC, and was potentiated by the depolarization produced by 10 mM TEA, a blocker of K+- channels. The spasmolytic effect of T does not involve DA release and binding to D2, since it was not reduced by 10 µ M metoclopramide. Also, T induced dose-dependent relaxation on the tonic contracture produced by high -[K+]o and ACh. By TLC there were detected in the leaves the presence of carvone, and flavonoids such as quercetin and hesperidin. By HPLC there were not found vitexin nor isovitexin, identified in A. citriodora. The monoterpene (-)- carvone non-competitively inhibited the ACh-DRC (pD'2 of 4.0±0.1) and the DRC of Ca2+ (pD'2 of 3.86±0.19), suggesting that the Ca2+- influx blockade is the mechanism of its antispasmodic effect. Results suggest that the antispasmodic effect of A. polystachya and A. gratissima are mostly explained by the non-competitive blockade of Ca+2 influx. It could be associated to the presence of flavonoids, and in the tinctures to some spasmolytic components of the essential oil such as carvone.
Résumé
Background Reactive oxygen species (ROS) have been implicated in the turnover of epithelial cells in the rat intestine. The metabolism of ethanol generates ROS, which are implicated in cellular injury, but the levels of lipid peroxidation in intestine in chronic alcoholism are unknown. Aim To investigate the effects of ethanol ingestion on lipid peroxidation, and anti- and pro-oxidant enzyme systems in enterocytes across the crypt–villus axis in intestine. Methods Wistar rats (90–100 g) were administered 1 mL of 30% ethanol daily for 39 days. Intestinal epithelial cells were isolated in fractions. Malondialdehyde levels, and activities of glutathione-S-transferase (GST), glutathione reductase (GR), superoxide dismutase (SOD) and catalase were determined in various cell fractions. Incorporation of H3- thymidine into DNA of enterocytes was also determined. Results Lipid peroxidation was elevated by two- to threefolds in both villus and crypt cells in ethanol-fed animals compared to controls. The activities of GST and GR were four- to six-folds higher in villus tip cells compared to crypt base cells. The activities of SOD and catalase were five- to seven-fold higher in crypt base cells compared to villus tip cells. Ethanol feeding elevated the activities of SOD (76-190%) and catalase (20-150%) in enterocytes all along the crypt–villus axis compared to the controls. H3 thymidine incorporation into DNA of enterocytes was reduced by half in ethanol-fed rats compared to controls. Conclusions There is a gradient in the concentration of lipid peroxides in enterocytes across the crypt–villus axis, being high at the villus tip and low at the crypt base in the rat intestine. Ethanol feeding enhanced lipid peroxidation in both villus and crypt cells.
Résumé
Gallic acid is a normal constituent of many edible foods, thus directly interacts with epithelial tissue in intestine. In the present study, the effect of gallic acid on intestinal alkaline phosphatase (IAP) and peptidase activities in rat intestine was evaluated. Gallic acid (0.27-0.5 mM) inhibited activities of leucine aminopeptidase (LAP) and -glutamyl transpeptidase (-GTP) by over 90%, compared to controls in rat intestine. In contrast, 0.1-0.6 mM gallic acid either had no effect or stimulated the activity of IAP in rat intestine. The observed inhibition of peptidases by gallic acid was reversible in nature. Kinetic analysis revealed no change in Vmax of LAP (0.42-0.44 units/mg protein) and -GTP (0.22-0.24 units/mg protein), while the values of apparent Km were increased 6-7 fold, exhibiting competitive-type of enzyme inhibition by gallic acid. The values of Ki for LAP and -GTP were 0.037 mM and 0.017 mM, respectively. These observations indicate that gallic acid is a potent inhibitor of brush border peptidases, and thus may interfere in the digestion and absorption of proteins in the intestine.