Estudo da permeabilidade de fármacos por meio do modelo de saco intestinal de ratos / Study of drug permeability through the rat gut sac model

Os parâmetros de permeabilidade e solubilidade são fundamentais à absorção oral de fármacos e a partir dessas características, foi criado o Sistema de Classificação Biofarmacêutica, através do qual os fármacos são divididos em quatro classes. Atualmente, para a determinação da solubilidade de um fármaco, existem diversos métodos padronizados por agências regulatórias, no entanto, para a determinação da permeabilidade, os ensaios são passíveis de diversas variações em sua execução, diminuindo a confiabilidade dos resultados obtidos e impossibilitando a comparação dos mesmos quando realizados com técnicas diferentes umas das outras. O objetivo do presente trabalho é avaliar as variáveis experimentais do modelo do saco intestinal que podem influenciar nos resultados de permeabilidade aparente de fármacos e na viabilidade do tecido. O presente estudo foi aprovado pelo Comitê de Ética no Uso de Animais da FCF-USP (109.2018-P574). Foram utilizados 33 Rattus norvegicus da linhagem Wistar, machos, jovens adultos, com peso entre 200 g e 300 g. Para realização do procedimento, cada animal permaneceu em jejum por cerca de quatro horas e após adequada anestesia a porção do jejuno do intestino delgado foi retirada e dividida em seis segmentos de aproximadamente 8,5cm cada. Foram realizados experimentos com e sem inversão do saco intestinal, submetidos a diferentes tempos de banho de gelo após sua ressecção, na presença ou ausência de inibidor da glicoproteína-P (verapamil). Os fármacos naproxeno e famotidina foram empregados como marcadores de alta e baixa permeabilidade, respectivamente. A losartana foi utilizada como substrato da glicoproteína P. Cada um dos sacos intestinais foi colocado em um tubo de ensaio contendo tampão Krebs, a 37°C, saturado com gás carbogênio. Para avaliação da integridade e viabilidade dos segmentos intestinais, observou-se a presença de movimentos peristálticos e coletaram-se amostras do meio de incubação nos tempos 0, 30, 45, 60, 90 e 120 minutos para quantificação dos fármacos e de glicose, uma vez que esta é ativamente transportada para a serosa do intestino delgado. Determinou-se a permeabilidade aparente de cada fármaco e as concentrações de glicose nas diferentes condições experimentais, realizou-se planejamento fatorial multinível e os resultados foram analisados por análise variância (ANOVA), seguida de pós-teste de Tukey. Observou-se que as variáveis experimentais interferiram de forma significativa na viabilidade tecidual e na permeabilidade aparente dos fármacos. Não foram observadas diferenças significativas da permeabilidade de fármacos nos diferentes segmentos do jejuno. A glicose mostrou-se um bom marcador de viabilidade tecidual e foi constatado que a presença ou ausência de movimentos peristálticos não está relacionada diretamente com a viabilidade do tecido. Uma vez que foram constatadas tantas interferências nos resultados, é imprescindível que os procedimentos experimentais sejam padronizados, para que os resultados apresentem menor variabilidade e possam ser comparados entre si

The permeability and solubility parameters are fundamental to the oral absorption of drugs and from these characteristics, the Biopharmaceutical Classification System was created, through which drugs are divided into four classes. Currently, for the determination of the solubility of a drug, there are several methods standardized by regulatory agencies, however, for the determination of permeability, the tests are subject to several variations in their execution, reducing the reliability of the results obtained and making it impossible to compare the results obtained. same when performed with different techniques. The aim of this study is to evaluate if different experimental conditions can influence the results of apparent drug permeability and tissue viability on gut sac model. The present study was approved by the Ethics Committee for the Use of Animals of FCF-USP (109.2018-P574). Thirty-three male, young adult Rattus norvegicus were used, weighing between 200 g and 300 g. To perform the procedure, each animal fasted for about four hours and after adequate anesthesia, the portion of the jejunum of the small intestine was removed and divided into six segments of approximately 8.5 cm each. Experiments were performed with and without inversion of the gut sac, submitted to different times of ice bath after its resection, in the presence or absence of a P-glycoprotein inhibitor (verapamil). The drugs naproxen and famotidine were used as markers of high and low permeability, respectively. Losartan was used as a substrate for P-glycoprotein. Each of the gut sacs was placed in a test tube containing Krebs buffer, at 37°C, saturated with carbogen gas. To evaluate the integrity and viability of the intestinal segments, the presence of peristaltic movements was observed and samples of the incubation medium were collected at 0, 30, 45, 60, 90 and 120 minutes for quantification of drugs and glucose, as it is actively transported to the serosa of the small intestine. The apparent permeability of each drug and the glucose concentrations were determined under different experimental conditions, multilevel factorial design was performed and the results were analyzed by analysis of variance (ANOVA), followed by Tukey's post-test. It was observed that the experimental variables significantly interfered in the tissue viability and in the apparent permeability of the drugs. No significant differences in drug permeability were observed in the different segments of the jejunum. Glucose proved to be a good marker of tissue viability and it was found that the presence or absence of peristaltic movements is not directly related to tissue viability. Since so many interferences were found in the results, it is essential that the experimental procedures be standardized, so that the results show less variability and can be compared between different authors

Differences in intestinal absorption characteristics of Laportea bulbifera extract in normal and rheumatoid arthritis model rats by isolated everted intestine model / 中国中药杂志

This work aimed to investigate the intestinal absorption characteristics of Laportea bulbifera extract in normal and rheumatoid arthritis model rats. The contents of neochlorogenic acid, chlorogenic acid, cryptochlorogenic acid, rutin, kaempferol-3-O-rutinoside, galuteolin, quercetin and isoquercetin in intestinal absorption solution samples were detected by UPLC-MS/MS with 5.0 g·L~(-1) as the absorption concentration. The cumulative absorption(Q) and absorption rate constant(K_a) were calculated, and the absorption characteristics of different components of L. bulbifera in intestinal absorption solution of normal rats and rheumatoid arthritis rats were compared. The results showed that all the eight index components in the extract of L. bulbifera could be absorbed into the intestinal capsule, the cumulative absorption-time curve of each component showed an upward trend without saturation, and the correlation regression coefficient(R~2) was greater than 0.92, which is consistent with the zero-order absorption rate process. It was speculated that the possible absorption mode of each component was passive diffusion. In normal condition, the absorption of ileum was the best(except chlorogenic acid), and in pathological condition, duodenum was the best. The total absorption of 8 components in each intestinal segment of RA rats was better than that of normal rats, which speculated that rheumatoid arthritis may change the specific site of drug absorption. The experimental results showed that rheumatoid arthritis could change the intestinal absorption of the extract of L. bulbifera, and its mechanism needs further study.

Effect of Acori Tatarinowii Rhizoma on Intestinal Absorption of Ginsenosides in Dingzhi Xiaowan / 中国实验方剂学杂志

Objective: To explore the effect of Acori Tatarinowii Rhizoma on intestinal absorption of ginsenosides in Dingzhi Xiaowan,and reveal the mechanism of Acori Tatarinowii Rhizoma acting as " adjuvant drug" in this formula. Method: The contents of ginsenoside Rg1,Re and Rb1 were measured by UPLC-MS/MS and the absorption of three ginsenosides in different intestine segments was investigated by rat single pass intestinal perfusion in situ,including absorption rate constant(Ka) and apparent permeability coefficient(Papp).Everted intestinal sac model was used to investigate the absorption dosage of three ginsenosides affected by volatile oil from Acori Tatarinowii Rhizoma and verapamil[Ver,a P-glycoprotein(P-gp) inhibitor]. Result:Papp values of three ginsenosides were ≤ 0.191×10-3 cm·min-1 in Dingzhi Xiaowan when lack of Acori Tatarinowii Rhizoma.Compared with lack of Acori Tatarinowii Rhizoma in Dingzhi Xiaowan group,the Ka and Papp values of lack of volatile oil from Acori Tatarinowii Rhizoma in Dingzhi Xiaowan group slightly increased without significant difference in the four intestinal segments,but when the prescription had Acori Tatarinowii Rhizoma,the Ka increased by 3.97-8.35 fold and the Papp increased by 3.99-8.49 fold.The results of everted intestinal sac test showed that volatile oil of Acori Tatarinowii Rhizoma could significantly promote the intestinal absorption of ginsenoside Rg1,Re and Rb1,but there was no dose-dependent. Conclusion:Volatile oil of Acori Tatarinowii Rhizoma can promote the intestinal absorption of three ginsenosides in Dingzhi Xiaowan,and the mechanism may be related to the inhibiting function on P-gp.

Effect of nano-TiO2 on intestinal glucose absorption in young rat on the everted gut sac model / 北京大学学报(医学版)

Objective: To study the effect of titanium dioxide (TiO2) nanoparticles on intestinal glucose absorption in young rats and its size effect.Methods: In the study, 63 small intestine segments were isolated from 63 Sprague-Dawley rats (SD rats, 4-week-old) to prepare the everted gut sac model.In the first part of our work, the everted sacs were exposed to 0, 50 mg/L TiO2 nanoparticles (24 nm) for 2 h with the presence of a series of glucose concentrations (10, 25, 50, 100, 200, 400, and 800 mmol/L), and the glucose absorbing function of the everted sacs were assessed in the process.On the basis of the work, utilizing the same method, further study was carried out to compare the effects of TiO2 nanoparticles (24 nm) and fine-particles (120 nm) on intestinal glucose absorbing function with the presence of 400 mmol/L glucose and 0, 10, 50, 200 mg/L TiO2.3 intestine segments were used in each group.Results: The cumulative glucose absorption increased with time extension and increased glucose concentration.In the first part of our work, with the presence of 400 mmol/L glucose, the group treated with 50 mg/L TiO2 nanoparticles showed significantly lower cumulative glucose absorption and glucose absorbing rate than the control group at the exposure time of 30 min (tcumulative absorption=3.254, P<0.05;tglucose absorbing rate=3.958, P<0.05), 90 min (tcumulative absorption=3.323, P<0.05;tglucose absorbing rate=3.063, P<0.05) and 120 min (tcumulative absorption=2.834, P<0.05;tglucose absorbing rate=3.002, P<0.05).At other glucose concentrations, statistically significant differences in cumulative glucose absorption or glucose absorbing rates were not found between the TiO2 nanoparticle exposed group and the control group.In the second part of our work, when compared with the control group, no significant downregulations in cumulative glucose absorption or glucose absorbing rates were observed in both TiO2 nano-particle treated group and TiO2 fine particle treated group.Differences between the TiO2 nanoparticle treated group and the TiO2 fine particle treated group were not statistically significant.Conclusion: Short-term exposure to TiO2 nanoparticles may downregulate the intestinal glucose absorbing function in young rats, and the difference with TiO2 fine particlesis is not obvious.

Overall intestinal permeability of multiple components in lotus leaves / 中国中药杂志

In the study of biopharmaceutics classification system of Chinese materia medica (CMMBCS), the interactions of multiple components in the absorption should be taken into consideration in simultaneous multi-component determination. To investigate the absorption of multiple components, the in vitro everted gut sac model was used in this study, wtih lotus leaves as the research object. Aquantitative analysis was also carried out for the known components in this study. Totally 19 components in lotus extracts were absorbed by the intestinal tract, the Papp levels of the known components were nuciferine (1×10⁻⁵-1×10⁻⁶ cm•s⁻¹), rutin (1×10⁻⁶-1×10⁻⁷ cm•s⁻¹), hyperoside (1×10⁻⁶ cm•s⁻¹), isoquercitrin (1×10⁻⁶-1×10⁻⁷ cm•s⁻¹) and astragalin (1×10⁻⁶-1×10⁻⁷ cm•s⁻¹), respectively. These components showed a low permeability under a multi-component environment. This study was carried out to lay a foundation for further relevant target studies for different categories of components.

Study on in vitro models of drug absorption / 中国临床药理学与治疗学

This article summarized some in vitro models of drug absorption,whose shortcomings and virtues were compared in order to be convenient for researchers to know and select optimal model.