柴胡疏肝散水提取物的肠吸收特性研究

目的 建立同时测定芍药苷、阿魏酸、芸香柚皮苷、柚皮苷、新橙皮苷、甘草酸含量的超高效液相色谱（UPLC）法,研究柴胡疏肝散水提物的肠吸收特性。方法 采用大鼠在体单向肠灌流和外翻肠囊实验模型,应用UPLC法测定柴胡疏肝散水提物中指标性成分（芍药苷、阿魏酸、芸香柚皮苷、柚皮苷、新橙皮苷和甘草酸）在不同时间点、不同部位肠道吸收量,计算吸收动力学参数,考察其肠吸收特征。结果 在体单向肠灌流模型结果表明,芍药苷、芸香柚皮苷、新橙皮苷、柚皮苷和甘草酸均为中等程度吸收的化学成分,而阿魏酸为完全吸收;外翻肠囊模型结果表明,芍药苷在空肠部位,阿魏酸、柚皮苷和新橙皮苷在十二指肠部位,芸香柚皮苷在十二指肠和空肠部位的吸收最佳,而甘草酸在各肠段的吸收无显著性差异。结论 肠道对柴胡疏肝散中6种指标性成分均有吸收,阿魏酸较其他5种指标性成分更易透过肠壁进入血液循环;不同肠段对6种指标性成分的吸收具有选择性。     

Localisation of drug permeability along the rat small intestine, using markers of the paracellular, transcellular and some transporter routes

The small intestine is the major site of drug absorption. Some reports in the literature have evoked the concept of “absorption windows” in the small intestine: are there specific regions where drug absorption is significantly higher than others? To investigate this question, we used an everted gut sac method to study the permeability of drugs and markers every 3–4 cm down the entire small intestine in rat. These markers were chosen to be representative of the mechanisms by which drugs cross the small intestinal mucosa: paracellular and transcellular passive diffusion, via influx transporters, and a drug (digoxin) that is effluxed from cells by P-glycoprotein (P-gp). The passive diffusion and influx transporter markers gave similar profiles with a plateau of permeability along the jejunum, and with the exception of L-Dopa, lower permeability in the ileum. Digoxin showed a linear decrease in the profile from the proximal jejunum to the ileum. Permeability in the duodenum was two to three times lower than the jejunum for all compounds. There were no narrow specific regions of high permeability and so the concept of discrete “absorption windows” along the small intestine as suggested from some pharmacokinetic studies may be related to other effects such as pH and/or solubility.     

Region-Dependent Role of the Mucous/Glycocalyx Layers in Insulin Permeation Across Rat Small Intestinal Membrane

The regional difference in the contribution of the mucous/glycocalyx layers in rat small intestine, as a diffusional or enzymatic barrier, to the absorption of insulin was investigated by in vitro studies. The mucous/glycocalyx layers from the duodenum, the jejunum, and the ileum in rat were successfully removed without damaging membrane integrity, by exposing them to a hyaluronidase solution in situ. In an in vitro transport experiment, the apparent permeability coefficient (P_app) of insulin for the hyaluronidase-pretreated group was significantly increased compared to the PBS-pretreated (control) group in all small intestinal regions, and the P_app of insulin in both PBS- and hyaluronidase-pretreated groups increased in the following order: duodenum < jejunum < ileum. On the other hand, irrespective of small intestinal regions, the P_app of FD-4 and of antipyrine, respectively the passive para- and transcellular permeation marker, exhibited no significant differences between PBS- and hyaluronidase-pretreated group. In addition, a significant amount of insulin was degraded in the mucous/glycocalyx layers compartment removed by hyaluronidase pretreatment, and the degradation activity in the mucous/glycocalyx layers showed regional differences in the following order: duodenum > jejunum > ileum. These findings suggest that, irrespective of small intestinal regions, the mucous/glycocalyx layers contributed to insulin permeation predominantly as an enzymatic barrier, and not as a diffusional barrier. Furthermore, the variation of the enzymatic activities in the mucous/glycocalyx layers and in the brush-border membrane would be one factor that accounts for the regional differences in the transport of insulin.     

Effects of Grapefruit Juice and Orange Juice on the Intestinal Efflux of P-Glycoprotein Substrates

Purpose. The aim of this study is to investigate the effects of 50% ethyl acetate extracts of grapefruit juice (GFJ) and orange juice (OJ) on the transport activity of P-glycoprotein (P-gp) in the rat small intestine. Methods.The efflux of P-gp substrates from rat everted sac in the absence or presence of verapamil, GFJ, OJ or erythromycin was measured. Rhodamine123, fexofenadine and saquinavir were used as P-gp substrates. P-gp expression levels in the rat jejunum and ileum were determined by Western blot analysis. Results. The efflux of rhodamine123 from the everted sac increased from the apex of the jejunum to the low ileum and the expression of P-gp in the ileum was 2.31-fold higher than that in the jejunum. Verapamil and the 50% GFJ and OJ extracts inhibited the efflux from the intestine of all three drugs tested. Erythromycin decreased the efflux of rhodamine123 and fexofenadine, but did not affect the efflux of saquinavir in the intestine. Conclusions. GFJ and OJ extracts inhibited the efflux of P-gp substrates from the small intestine. Therefore, they may enhance the oral bioavailability of P-gp substrates by increasing absorption in the small intestine.     

Absorption of paraquat by rat gut in vitro

The absorption of radioactively labeled paraquat was measured in rat ileum, jejunum and colon by a micro everted sac technique (Semenza and Mühlhaupt, 1969). The absorption rate increased linearly over the range of concentrations measured (10^–5 to 10^–2 M) and was enhanced by nearly 50% in the absence of sodium ions. The absorption rate decreased in the order: ileum, jejunum, colon whereby in the colon still 65% of the values of the small intestine were observed.     

杏香兔耳风提取物的小肠吸收机制

目的研究杏香兔耳风提取物的小肠吸收机制,并初步考察小肠上皮细胞一元羧酸转运蛋白对提取物吸收的影响。方法采用外翻肠囊模型,以杏香兔耳风提取物中绿原酸和3,5-二咖啡酰基奎宁酸为主要成分考察总酚酸在不同肠段(空肠、回肠)中的膜通透性,同时通过吸收抑制(阿魏酸、苯甲酸、布洛芬)试验,考察了一元羧酸转运蛋白对绿原酸和3,5-二咖啡酰基奎宁酸吸收的影响。结果在空肠和回肠中,绿原酸比3,5-二咖啡酰基奎宁酸的小肠渗透率都要高。三种抑制剂(阿魏酸、苯甲酸、布洛芬)可使绿原酸和3,5-二咖啡酰基奎宁酸在回肠的渗透率降低;对绿原酸和3,5-二咖啡酰基奎宁酸在空肠的渗透率影响较小。结论绿原酸和3,5-二咖啡酰基奎宁酸在小肠的吸收属于一级动力学过程,吸收机制为被动扩散。但是同时还存在以一元羧酸转运蛋白介导的主动转运。     

外翻肠囊法研究金芪降糖片的肠吸收特性

目的:研究金芪降糖片中主要化学成分的肠吸收特性。方法:采用大鼠离体外翻肠囊模型,收集金芪降糖片3种剂量在肠道不同部位给药后不同时间的肠囊液样品,用HPLC对有效成分进行检测分析,计算各有效成分的累积吸收量(Q)及吸收速率常数(K_a)以分析它们在肠道的吸收特征。结果:可检测到金芪降糖片中的9个成分吸收进入肠囊,分别为新绿原酸、隐绿原酸、绿原酸、咖啡酸、表小檗碱、黄连碱、药根碱、巴马汀、小檗碱。金芪降糖片中的9个成分在不同肠段不同浓度下的吸收均为线性吸收,其回归相关系数(R²)均大于0.9,符合零级吸收,且9个成分的K_a值在不同肠段均随药物剂量的增加而增加(P<0.05),表明其为被动吸收。肠道不同部位的吸收实验表明,以金芪降糖片高剂量中绿原酸和小檗碱在120 min的累积吸收量为例,绿原酸在各肠段的累积吸收量分别为:十二指肠,626.9 μg;空肠,1 116.8 μg;回肠,516.9 μg;结肠,215.8 μg,小檗碱在各肠段的累积吸收量分别为:十二指肠,178.6 μg;空肠,208.6 μg;回肠,97.5 μg;结肠,66.8 μg。说明空肠对各成分的吸收最为明显,其次是回肠,且有机酸类成分的在肠吸收优于生物碱类成分。结论:金芪降糖片中4个有机酸类成分及5个生物碱类成分可吸收进入肠囊,各成分的吸收形式可能为被动吸收。     

千金藤素对非索非那定肠吸收的影响

目的研究千金藤素对非索非那定大鼠肠吸收的影响。方法采用大鼠肠外翻模型,以维拉帕米为阳性对照,研究千金藤素对非索非那定肠吸收的影响,并用反相高效液相色谱法测定大鼠肠黏膜内外两测的非索非那定浓度。结果非索非那定在大鼠十二指肠有吸收,千金藤素能增加非索非那定的吸收。结论千金藤素能增加非索非那定吸收,机制可能是抑制了P-糖蛋白的外排。     

广枣提取物大鼠肠外翻的吸收研究

目的研究广枣提取物中2种主要代表性成分没食子酸和原儿茶酸在大鼠不同肠段、不同时间的吸收规律。方法构建大鼠肠外翻模型,应用HPLC法测定广枣提取物肠吸收液中没食子酸和原儿茶酸含量,计算其吸收参数,并分析其在大鼠小肠不同部位、不同时间的吸收特征。结果 2.5h为肠外翻最终检测时间点,在建立的分析色谱条件下,没食子酸和原儿茶酸色谱峰处台氏液和广枣提取物中其他成分对其无干扰,专属性良好。广枣提取物中原儿茶酸和没食子酸在各肠段均为线性吸收,r2值均达到0.90以上,不同肠道部位的累计吸收结果为:十二指肠>空肠>回肠>结肠。结论广枣提取物中原儿茶酸和没食子酸在肠道的吸收特征符合零级吸收速率,其最佳吸收部位为十二指肠。     

外翻肠囊法研究茶芎苯酞类有效部位中4种成分的肠吸收特性

目的:研究茶芎苯酞类有效部位(CPTA)中4种成分在大鼠离体肠中的最佳吸收部位、吸收机制和吸收动力学过程,为CPTA剂型与处方设计提供生物药剂学依据.方法:采用大鼠离体外翻肠囊模型,利用HPLC法建立CPTA中4种成分在小肠液中的含量测定方法.取麻醉后大鼠的十二指肠、空肠、回肠和结肠段作为受试肠段建立外翻肠囊模型,计算...     

金莲花汤中葛根素、牡荆素、迷迭香酸和咖啡酸的肠吸收研究

目的 考察金莲花汤中葛根素、牡荆素、迷迭香酸和咖啡酸的肠吸收特性,确定金莲花汤中活性成分。方法 采用HPLC法测定肠吸收样品中咖啡酸、葛根素、牡荆素、迷迭香酸,以大鼠肠外翻吸收实验和Caco-2细胞模型转运实验计算各成分的累积吸收量、吸收速率常数和表观渗透系数。结果 随着金莲花汤的质量浓度增加,咖啡酸、葛根素、牡荆素、迷迭香酸的吸收速率常数呈线性关系增加,符合零级吸收速率,且吸收率均小于1.4%,在肠道中吸收效果普遍较差,其中咖啡酸的吸收较为明显。各成分的表观渗透系数值大小为迷迭香酸>咖啡酸>葛根素>牡荆素。结论 金莲花汤中葛根素、牡荆素、迷迭香酸和咖啡酸均可在肠道中被吸收,吸收方式为被动扩散,咖啡酸和迷迭香酸可能是金莲花汤中发挥药效的活性物质,葛根素和牡荆素可能是前药。     

Effects of Various Protease Inhibitors on the Intestinal Absorption and Degradation of Insulin in Rats

The effects of protease inhibitors on the intestinal absorption of insulin were investigated in situ in closed small and large intestinal loops in rats, and the stability of insulin was examined in homoge-nates of the small and large intestine. The intestinal absorption of insulin was evaluated by its hypoglycemic effect. When insulin alone was administered into small or large intestinal loops, no marked hypoglycemic response was observed in either region. Of the coadministered protease inhibitors, soybean trypsin inhibitor (1.5, 10 mg/ml) marginally promoted insulin absorption from the large intestine, whereas aprotinin (10 mg/ml) did to a moderate degree. However, a significant hypoglycemic effect was obtained following large intestinal administration of insulin with 20 mM of Na-glycocholate, camostat mesilate and bacitracin, when compared with the controls. In contrast, we found little hypoglycemic effect following small intestinal coadministration of insulin with these protease inhibitors. In the stability experiment, bacitracin, camostat mesilate and Na-glycocholate were effective in reducing insulin degradation in both small and large intestinal homogenates. It was found that the reduction in the proteolytic rate of insulin was related to the decrease in plasma glucose concentration by these protease inhibitors in the large intestine. These findings suggest that coadministration of protease inhibitors would be useful for improving the large intestinal absorption of insulin.     

Changes in Intestinal Absorption of 5-Fluorouracil-Treated Rats

Abstract: 5-Fluorouracil chemotherapy is often accompanied by gastrointestinal toxicity. In this study, we investigated the effect of 5-fluorouracil on the epithelial barrier function of rat small intestine by examining the absorption of a poorly absorbable marker, fluorescein isothiocyanate-labelled dextran (molecular weight 4,400). We further evaluated the intestinal absorption of 5-fluorouracil in rats treated orally with 5-fluorouracil once daily for 4 days. The small intestinal absorption of fluorescein isothiocyanate-labelled dextran and 5-fluorouracil was tested using in situ closed loop intestine technique and in vitro everted intestine technique, respectively. After administration of 5-fluorouracil to rats for 4 days, the body weight of rats decreased significantly and the fluorescein isothiocyanate-labelled dextran concentration in plasma increased significantly, compared with that of control rats to which the saline solution alone was administered. Moreover, the intestinal absorption of 5-fluorouracil in the 5-fluorouracil-treated rats was enhanced significantly, compared with that of control rats. The administration of 5-fluorouracil to rats caused body weight loss and epithelial barrier dysfunction of the small intestine in rats as shown by the increased permeation of the high molecular weight compound, fluorescein isothiocyanate-labelled dextran. The increased absorption of 5-fluorouracil after this treatment suggest that the 5-fluorouracil toxicity might be amplified by its treatment.     

Role of glucose transporters in the intestinal absorption of gastrodin,a highly water-soluble drug with good oral bioavailability

Abstract

Gastrodin, a sedative drug, is a highly water-soluble phenolic glucoside with poor liposolubility but exhibits good oral bioavailability. The current study aims to investigate whether glucose transporters (GLTs) are involved in the intestinal absorption of gastrodin. The intestinal absorption kinetics of gastrodin was determined using the rat everted gut sac model, the Caco-2 cell culture model and the perfused rat intestinal model. In vivo pharmacokinetic studies using diabetic rats with high GLT expression were performed. Saturable intestinal absorption of gastrodin was observed in rat everted gut sacs. The apparent permeability (Papp) of gastrodin from the apical (A) to basolateral (B) side in Caco-2 cells was two-fold higher than that from B to A. Glucose or phlorizin, a sodium-dependent GLT (SGLT) inhibitor, reduced the absorption rates of gastrodin from perfused rat intestines. In vivo pharmacokinetic studies showed that the time of maximum plasma gastrodin concentration (T_max) was prolonged from 28 to 72?min when orally co-administered with four times higher dose of glucose. However, the T_max of gastrodin in diabetic rats was significantly lowered to 20?min because of the high intestinal SGLT1 level. In conclusion, our findings indicate that SGLT1 can facilitate the intestinal absorption of gastrodin.     

外翻肠囊法研究奥硝唑对映体在大鼠不同肠段的吸收特性

目的考察奥硝唑在大鼠各肠段的吸收特性及奥硝唑两手性对映体在大鼠不同肠段吸收的差异性。方法采用大鼠外翻肠囊法,以HPLC手性色谱柱法测定奥硝唑在不同肠段的吸收量以及S-奥硝唑及R-奥硝唑的同一肠段肠吸收量,并分别计算吸收速率常数(Ka)和表观渗透系数(P_(app)),同法考察了P-蛋白抑制剂(维拉帕米和环孢素A)对奥硝唑肠吸收特性的影响。结果奥硝唑在不同肠段吸收均呈线性,符合零级药物吸收速率,吸收趋势为空肠>回肠>结肠。在空肠段两对映体以近于1∶1的比例同时吸收,吸收速率不存在显著差异,随着供试液中奥硝唑质量浓度的上升,Ka呈线性增加(R~2>0.99),Paap基本保持不变,P-蛋白抑制剂对奥硝唑的肠吸收没有显著性影响(P>0.05)。结论奥硝唑在不同肠段的吸收有差异,空肠部位是吸收的最佳部位(P<0.05),S-奥硝唑与R-奥硝唑在肠道中吸收速率不存在显著差异,吸收以被动扩散机制为主,奥硝唑不是P-糖蛋白的底物。     

Comparison Between Permeability Coefficients in Rat and Human Jejunum

Purpose. Our main aim is to determine the effective intestinal permeability (P_eff) in the rat jejunum in situ for 10 compounds with different absorption mechanisms and a broad range of physico chemical properties, and then compare them with corresponding historical human in vivo P_eff values. Methods. The rat P_eff coefficients are determined using an in situ perfusion model in anaesthetized animals. The perfusion flow rate used is 0.2 ml/min, which is 10 times lower than that used in humans. The viability of the method is assessed by testing the physiological function of the rat intestine during perfusions. Results. The P_eff for passively absorbed compounds is on average 3.6 times higher in humans compared to rats (P_eff,man = 3.6 · P_eff,rat + 0.03·10^–4; R^2 = 1.00). Solutes with carrier-mediated absorption deviate from this relationship, which indicates that an absolute scaling of active processes from animal to man is difficult, and therefore needs further investigation. The fraction absorbed of drugs after oral administration in humans (fa) can be estimated from 1 – e^–(2·P _eff,man ^·t _res ^/r·2.8). Conclusions. Rat and human jejunum P_eff estimates of passively absorbed solutes correlate highly, and both can be used with precision to predict in vivo oral absorption in man. The carrier-mediated transport requires scaling between the models, since the transport maximum and/or substrate specificity might differ. Finally, we emphasize the absolute necessity of including marker compounds for continuous monitoring of intestinal viability.     

Effect of curcumin on glucose absorption: an experimental study on albino rats

Curcumin derived from the rhizome Curcuma longa is one of the primary ingredient in turmeric. Turmeric is used frequently as food additive in Asia, specially the Indian subcontinent. The daily intake of turmeric in the diet may therefore expose the gut to curcumin and affect its physiological functions, including the absorption of nutrients from small intestine. However, no published reports are available on the effect curcumin on absorption of nutrients from small intestine. To explore this possibility, transport of glucose from small intestine was studied in adult albino rats following feeding the animals curcumin intragastrically for five consecutive days. The controls were fed simultaneously, the vehicular fluid intragastrically in the identical volume. Transport of glucose from small intestine was studied using everted sac technique of Wilson and Wiseman (1954) on animals fasted for 16-20 hrs. Everted sacs were prepared from both jejunal and ileal portion of small intestine. Observations showed a significant increase in glucose transport from jejunal and upper ileal portion of small intestine suggesting that curcumin does influence the transport of nutrients from the gut.     

Changes in Intestinal Mucosal Permeability Caused by Nonprotein Thiol Loss in Rats

The barrier selectivity of the intestinal mucosal membrane permeability may be impaired in certain disease conditions. Membrane permeability was previously shown to be correlated with changes in nonprotein thiol in rat intestinal tissue by the everted sac method. In the present study, the mucosal effects of alloxan-induced diabetes and chronic alcohol administration to intact rats, as well as pre-treatment with diethyl maleate, ethanol, and salicylate, were investigated. In each case, a drop of mucosal nonprotein thiol was associated with an increased absorption of cefoxitin, cefmetazole, and phenol red, hydrophilic compounds that are poorly absorbed through intact membrane, and with a decreased absorption of L-phenylalanine. The effect of nonprotein thiol loss on rectal absorption of cefoxitin, cefmetazole, and phenol red was greater than that on the small intestinal absorption. The increase in phenol red absorption by diethyl maleate in the in vitro everted sac method correlated with Ca²⁺ release from the intestinal mucosa, which was induced by nonprotein thiol loss. Resistance to the effect of nonprotein thiol loss on Ca²⁺ homeostasis was greater in rat ileum than in rat colon (including rectum). The administration of cysteamine as an exogenous nonprotein thiol restored non-protein thiol levels in the mucosa along with the barrier function of the intestinal mucosa to the absorption of cefoxitin, cefmetazole, and phenol red. In contrast, the transport of L-phenylalanine in the small intestinal mucosa was not restored by cysteamine treatment.     

Age-Dependent Intestinal Absorption of Valproic Acid in the Rat

The absorption of valproic acid (VPA) across isolated perfused segments of jejunum, ileum and colon was examined in situ in 14-day-to 24-month-old Fischer-344 rats. Within each age group, the intrinsic absorptive clearance (C1_a) of VPA at a perfusate concentration of 1 mg/ml was highest in the jejunum, lowest in the colon, and intermediate in the ileum. When intestinal Cl_a was normalized for the dry weight of the segment, within-group variability decreased. In all segments, VPA Cl_a normalized by dry weight decreased during development (20 to 90 days) and remained relatively constant during aging (90 days to 24 months). The mechanism of valproate absorption (active vs. passive) was examined across age in everted intestinal sacs prepared from each of the three segments. Data were consistent with active transport of VPA in the jejunum and ileum of rats of all ages, and in the colon of pre-weanling animals. Colonic absorption of VPA appeared to occur by passive diffusion in adult rats. In contrast, colonic absorption of d-glucose occurred only by passive diffusion in all age groups. These data indicate that, during development, significant alterations in the rate of VPA absorption occur throughout the rat intestine. Furthermore, while active transport of VPA by the small intestine was present throughout the age range investigated, active transport by the colon became negligible by the time of weaning.