Bile acid and bile salt disrupt gastric mucosal barrier in the dog by different mechanisms

Characterizing the Physicochemical Properties of Two Weakly Basic Drugs and the Precipitates Obtained from Biorelevant Media

Generally, some weakly basic insoluble drugs will undergo precipitate and redissolution after emptying from the stomach to the small intestinal, resulting in the limited ability to predict the absorption characteristics of compounds in advance. Absorption is determined by the solubility and permeability of compounds, which are related to physicochemical properties, while knowledge about the absorption of redissolved precipitate is poorly documented. Considering that biorelevant media have been widely used to simulate gastrointestinal fluids, sufficient precipitates can be obtained in biorelevant media in vitro. Herein, the purpose of this manuscript is to evaluate the physicochemical properties of precipitates obtained from biorelevant media and active pharmaceutical ingredients (API), and then to explore the potential absorption difference between API and precipitates. Precipitates can be formed by the interaction between compounds and intestinal fluid contents, leading to changes in the crystal structure, melting point, and melting process. However, the newly formed crystals have some advantageous properties compared with the API, such as the improved dissolved rate and the increased intrinsic dissolution rate. Additionally, the permeability of some precipitates obtained from biorelevant media was different from API. Meanwhile, the permeability of rivaroxaban and Drug-A was decreased by 1.92-fold and 3.53-fold, respectively, when the experiments were performed in a biorelevant medium instead of a traditional medium. Therefore, the absorption of precipitate may differ from that of API, and the permeability assay in traditional medium may be overestimated. Based on the research results, it is crucial to understand the physicochemical properties of precipitates and API, which can be used as the departure point to improve the prediction performance of absorption.

Effect of the ulcerogenic agents ethanol, acetylsalicylic acid and taurocholate on actin cytoskeleton and cell motility in cultured rat gastric mucosal cells

AIM: To assess the effects of ulcerogenic agents on actin cytoskeleton and cell motility and the contribution of oxidative stress.

METHODS: Rat gastric mucosal cell monolayers were cultured on coverslips. The cells were exposed, with or without allopurinol (2 mmol/L), for 15 min to ethanol (10-150 mL/L), ASA (1-20 mmol/L) or taurocholate (1-20 mmol/L), then the cells were processed for actin and vinculin staining. Cell migration after wounding was also measured.

RESULTS: Exposure to 10 mL/L ethanol caused divergence of zonula adherens-associated actin bundles of adjacent cells and decreased rate of migration. These actions were opposed by xanthine oxidase inhibitor allopurinol. Exposure to 50 mL/L ethanol induced degradation and divergence of zonula adherens-associated vinculin from adjacent cells, which was, again, partially reverted by allopurinol. With 1 mmol/L ASA actin filaments became shorter and thicker. However, higher concentrations (10, 20 mmol/L) of ASA returned microfilaments thinner and longer, and decreased rate of migration. Zonula adherens-associated actin bundles were moderately distorted with 10 mmol/L ASA and with 10 mmol/L taurocholate. Exposure to taurocholate provoked changes resembling those of ASA. Taurocholate 5-20 mmol/L decreased the rate of migration dose dependently. The effects of ASA and taurocholate were not prevented by allopurinol.

CONCLUSION: All ulcerogenic agents decreased the rate of migration dose dependently and induced divergence of zonula adherens-associated actin bundles of adjacent cells. In addition, ethanol and ASA caused degradation of actin cytoskeleton. Oxidative stress seems to underlie ethanol, but not ASA or taurocholate, induced cytoskeletal damage.

Acid pH enhances the effects of taurodeoxycholate on water and solute transport in the human and rat jejunum

The relative rate of unspecific binding of bile acids to brush border membrane vesicles resembles their relative potencies as intestinal secretagogues. This interaction of bile acids with brush border membranes is enhanced in an acid environment. We, therefore, studied the effects of taurodeoxycholate and taurocholate on water and solute transport at pH 7.6 and pH 4.0 in the human and rat jejunum. Five mM taurodeoxycholate induced significantly greater fluid secretion in the human jejunum at pH 4.0 than at pH 7.6 (p less than 0.02; n = 5), 10 mM taurocholate (n = 4) had no effect at either pH. In the rat 15 mM taurodeoxycholate at pH 4.0 induced greater fluid secretion (p less than 0.01; n = 6), released more phospholipid (p less than 0.001; n = 4) and enhanced absorption of mannitol more than at pH 7.6 (p less than 0.05; n = 6). In contrast fluid secretion and release of phospholipids induced by Triton X-100 were not affected by pH (n = 6), nor was fluid secretion induced by cholera toxin (n = 8). The data suggest that the enhancement of the secretory effect of taurodeoxycholate in an acid environment is due to its increased interaction with the mucosal surface, and support the concept that the ability of detergents to interact with the intestinal brush border membrane determines their effectiveness as intestinal secretagogues.