CYP3A和P-糖蛋白对布格呋喃在大鼠小肠吸收的影响

本研究采用大鼠小肠在体单向 (single-pass) 灌流模型, 收集灌流后不同时间点灌流液和肠系膜静脉血, 应用GC-MS联用法测定灌注液和血浆中的布格呋喃含量, 并计算布格呋喃渗透系数［P_lumen = −(Q/2πrl) Ln(C_out/C_in) 和P_blood = (ΔM_B/Δt)/(2πrl)］, 从而反映布格呋喃的代谢变化。同时, 观察CYP3A选择性抑制剂醋竹桃霉素 (TAO)、CYP3A和P-糖蛋白 (P-gp) 共同抑制剂环孢素A (CsA) 和P-gp选择性抑制剂LSN335984对布格呋喃自大鼠肠道吸收的影响。结果表明, 在大鼠小肠在体单向灌流模型中加入LSN335984、TAO和CsA后, 大鼠肠系膜静脉血中布格呋喃的累积量分别为73.4、82.9和98.3 pmol·cm⁻², 与对照组比较分别增加3.9倍、4.6倍和5.6倍, 代谢分别减少12%、11%和21%。提示CYP3A和P-gp选择性抑制剂可明显减少布格呋喃在大鼠肠道的首过效应, 促进布格呋喃的肠道吸收。由此可见, P-gp与CYP3A两者联合作用是引起布格呋喃口服生物利用度低的重要因素, 两者对布格呋喃小肠吸收均具有重要影响。     

左旋紫草素肠道转运及Caco-2细胞转运特性

目的研究左旋紫草素肠道及Caco-2细胞转运特征及其机制。方法应用翻转肠囊法和Caco-2细胞模型考察时间、浓度对左旋紫草素转运吸收特性的影响,应用P-糖蛋白抑制剂维拉帕米对左旋紫草素转运吸收机制进行研究,采用HPLC法测定左旋紫草素的浓度,计算其表观渗透系数(Papp)。结果在Caco-2细胞模型,随浓度增加和时间延长,左旋紫草素的累积转运量逐渐增加;加用维拉帕米后,使AP侧到BL侧的表观渗透系数Papp(AP→BL)显著增加,而从BL侧到AP侧的表观渗透系数Papp(BL→AP)显著降低。在翻转肠囊模型,100μmol·L-1左旋紫草素中加入维拉帕米后Papp显著增加。结论左旋紫草素的转运存在被动转运和主动转运2种形式,P糖蛋白参与主动转运过程;该药经肠道吸收中等,加入维拉帕米可能促进吸收。     

灯盏细辛提取物中3种活性成分在Caco-2细胞模型吸收机制的研究

目的研究灯盏细辛提取物(erigeron breviscapus extract,Ebe)中3种活性成分灯盏甲素、咖啡酸和绿原酸的吸收机制。方法建立人结肠腺癌细胞系(the human colon carcinoma cell line,Caco-2细胞)模型;利用该模型研究Ebe的细胞摄取规律,通过UPLC-MS/MS法测定Caco-2细胞中灯盏甲素、咖啡酸和绿原酸的浓度,研究pH、时间以及药物浓度对3种活性成分的转运影响;考察在P-糖蛋白抑制剂(维拉帕米、环孢素A)存在与否时3种活性成分在Caco-2细胞模型中的转运情况。结果受试物Ebe在所设置的浓度范围内(0.1~25.0 g·L~(-1))对Caco-2细胞无毒副作用。灯盏甲素和绿原酸在Caco-2细胞摄取实验中具有浓度、时间依赖性,呈正相关,渗透系数维持在一个平衡状态。咖啡酸具有浓度饱和性,且加入P-糖蛋白抑制剂后咖啡酸的细胞摄取量明显增加。结论 Ebe中灯盏甲素和绿原酸主要表现为被动转运,P-糖蛋白参与了咖啡酸的摄取过程,咖啡酸的吸收主要由载体媒介转运实现。     

隐丹参酮在小肠吸收机制的实验研究

目的研究隐丹参酮在大鼠小肠的吸收机制。方法用大鼠在体一过式肠灌流方法，通过肠系膜静脉插管采集血样，同时收集灌流流出液，以高效液相色谱法测定样品中隐丹参酮含量，计算其通透率。结果隐丹参酮在大鼠小肠的肠管通透率(Plumen)和血管通透率(Pbtood)随浓度的增加而下降；加入P-糖蛋白抑制剂维拉帕米后其通透率增高。结论隐丹参酮在大鼠小肠的转运机制可能为主动转运，隐丹参酮可能为P-糖蛋白底物。     

P-糖蛋白抑制剂对蝙蝠葛碱跨膜转运的影响

目的 研究Caco-2细胞模型中P-糖蛋白抑制剂对蝙蝠葛碱跨膜转运的影响.方法 采用HPLC法测定转运液中蝙蝠葛碱的含量;采用Caco-2细胞模型双向转运实验,考察不同浓度维拉帕米、环孢素A和醋酸地塞米松3种p-糖蛋白抑制剂对蝙蝠葛碱跨膜转运的影响.结果 加入3种P-糖蛋白抑制剂后,蝙蝠葛碱的Papp(A-B)均有一定程度增加,而Papp(B-A)均有显著降低(P＜0.05),即均抑制了蝙蝠葛碱的外排转运.结论 外排转运体P-糖蛋白对蝙蝠葛碱有外排作用,蝙蝠葛碱可能为P-糖蛋白底物.     

芦丁在Caco-2细胞模型中吸收和外排机制的研究

利用Caco-2细胞模型研究芦丁在小肠上皮的摄取、跨膜转运及外排动力学机制,评价孵育时间、芦丁浓度、p-糖蛋白抑制剂环孢素A和多药耐药相关蛋白抑制剂维拉帕米对芦丁的细胞摄取与转运的影响.结果表明,药物摄取量与孵育时间、药物浓度呈正相关,环孢素A和维拉帕米对芦丁的细胞摄取量无显著影响(P＞0.05).不同浓度药物从基底侧(basolateral,BL)到肠腔侧(Apical,AP)的表观渗透系数Papp,BL-AP与AP到BL的Papp,AP-BL比值均在0.5～1.5.试验结果提示芦丁是以被动扩散为主要转运方式被小肠上皮细胞摄取和转运,且不受外排蛋白外排作用的影响.     

新抗癌活性物AG337在Caco-2细胞模型中经p-糖蛋白介导的跨细胞转运

目的研究AG337在Caco-2细胞模型中的转运机制.方法改变药物浓度和实验温度以及他用合适抑制剂,测定AG337的跨细胞转运速率及其在细胞内的累积量.结果AG337的跨细胞转运显示强烈的有向性,B→A转运(细胞绒毛而Apical→基底面Basolateral)大于A→B10倍以上,P-糖蛋白的专属抑制剂维拉帕米(Ver)可以消除这种有向性温度从37℃至4℃时B→A的转运速率下降50倍,而A→B下降不大.结论AG337在Caco-2模型中的跨细胞转运.受到P-糖蛋白强烈的外排作用.     

基于大鼠在体单向肠灌流模型研究P-糖蛋白抑制剂对蝙蝠葛碱肠吸收的影响

目的:研究P-糖蛋白抑制剂对蝙蝠葛碱肠吸收的影响。方法:采用在体单向肠灌流法进行小肠吸收实验,利用HPLC法测定灌流液中蝙蝠葛碱的浓度,考察不同浓度P-糖蛋白抑制剂环孢素A、醋酸地塞米松和维拉帕米对蝙蝠葛碱肠吸收的影响。结果:与对照组相比,高浓度和中浓度环孢素A对蝙蝠葛碱的Ka、Papp、P%、吸收量和累积吸收量均有显著性影响(P<0.05),而低浓度时上述参数差异无显著性(P>0.05);与对照组相比,高、中、低3个浓度醋酸地塞米松对蝙蝠葛碱的Ka、Papp、P%、吸收量和累积吸收量均有显著性影响(P<0.05);与对照组相比,高浓度维拉帕米对Dau的Ka、Papp、P%、吸收量和累积吸收量均有显著性影响(P<0.05),而中浓度和低浓度时上述参数无显著性差异(P>0.05)。结论:P-糖蛋白抑制剂环孢素A、醋酸地塞米松和维拉帕米对蝙蝠葛碱均有促吸收作用,其作用大小顺序为醋酸地塞米松>环孢素A>维拉帕米;P-糖蛋白对Dau的肠吸收有外排作用,蝙蝠葛碱为P-糖蛋白底物。     

布洛芬在Caco-2细胞模型中的转运行为考察

采用Caco-2细胞单层模型考察了布洛芬的吸收机制.用HPLC法测定了磷酸盐缓冲液中布洛芬的转运量.结果显示,布洛芬的转运量受培养时间、浓度和P-糖蛋白抑制剂维拉帕米的影响,其表观渗透系数为1×10-6～7×10-6cm/s,且双向转运的表观渗透性存在方向性差异.这提示布洛芬在Caco-2细胞模型中以主动转运和被动扩散两种机制吸收,且存在P-糖蛋白介导的外排机制.     

蒙药塔布森-2中9种苯丙素类成分在Caco-2细胞中的吸收特性研究

目的 研究蒙药塔布森-2(Tabson-2 decoction,TBD)中苯丙素类成分在Caco-2细胞中的吸收特性,初步阐明TBD的口服吸收机制。方法 采用Caco-2细胞单层细胞模型,通过UPLC-MS/MS分析TBD在Caco-2细胞中的摄取成分,并建立UPLC-MS/MS分析方法测定TBD中吸收最好的9种苯丙素类成分原儿茶酸、新绿原酸、绿原酸、隐绿原酸、1,5-二咖啡酰奎宁酸、异绿原酸C、咖啡酸、二氢咖啡酸、3-羟基肉桂酸在Caco-2细胞中的含量,分别考察时间、浓度和P糖蛋白抑制剂对各成分的吸收影响。结果 研究发现咖啡酸、二氢咖啡酸的总摄取量在0~180 min为上升趋势,未呈现饱和;3-羟基肉桂酸在90 min左右吸收恒定趋于饱和;隐绿原酸、1,5-二咖啡酰奎宁酸、异绿原酸C、新绿原酸、绿原酸、原儿茶酸的摄取量约从90 min开始,随时间的增加先下降后上升。与苯丙素类成分相比,加入P-糖蛋白抑制剂维拉帕米及环孢菌素A后对二氢咖啡酸的吸收产生了影响,说明二氢咖啡酸是P-糖蛋白底物。结论 TBD主要苯丙素类成分进入Caco-2细胞以被动扩散为主,主动转运为辅,且除二氢咖啡酸外其他8个成分的吸收过程不受P-糖蛋白的外排作用影响。     

Limited role of P-glycoprotein in the intestinal absorption of cyclosporin A

The contribution of P-glycoprotein (P-gp) to the intestinal absorption of cyclosporin A (CsA) was investigated by comparing the in vivo pharmacokinetics of CsA in P-gp knockout mice versus wild-type mice following both oral and intravenous administration and by examining the transport of CsA across Caco-2 cell monolayers. The apparent oral bioavailability of CsA in P-gp knockout mice was 1.55-fold larger than in wild-type mice, leading to an apparent absolute bioavailability of 41.8%. A concentration dependent efflux transport of CsA across Caco-2 cell monolayers was found, which exhibited saturation at a CsA concentration of 1 muM. These results suggest that the involvement of P-gp in the intestinal absorption of CsA is not as profound as was previously thought.     

大鼠小肠原位灌流与Caco-2细胞法研究柠檬苦素吸收机制

柠檬苦素广泛存在于柑橘类水果中, 具有抗菌、抗病毒、镇痛、抗炎和抗癌等活性, 但其口服生物利用度较低。本文意在研究柠檬苦素在肠道内的吸收机制, 为其今后的研究奠定基础。实验通过大鼠原位肠灌流和体外Caco-2细胞法进行。大鼠原位肠灌流结果显示, 柠檬苦素可能通过肠道促进扩散机制吸收, 吸收差且在全肠段都有吸收, 没有部位选择性。Caco-2细胞实验结果显示, 维拉帕米和酮康唑能显著提高柠檬苦素的吸收, 而丙磺舒的影响不明显。柠檬苦素吸收较低和生物利用度较差, 可能是P-gp外排以及CYP3A4代谢共同参与的结果。柠檬苦素的肠吸收机制研究将为其剂型设计和临床应用提供重要的参考。     

Transport characteristics of 9-nitrocamptothecin in the human intestinal cell line Caco-2 and everted gut sacs

The intestinal absorptive characteristics and the efflux mechanisms of 9-nitrocamptothecin (9-NC), a novel water-insoluble camptothecin (CPT) derivative, were investigated. The Caco-2 cells and the everted gut sacs were used as models of the intestinal mucosa to assess transepithelial transport of 9-NC. The determination of 9-NC was performed by HPLC. In the Caco-2 cells, the absorptive transport of 9-NC was pH dependent and the transport was enhanced at weakly acidic pH on the apical side. No concentration dependence and saturation were observed for the absorptive transport of 9-NC at concentrations up to 250 microM, while secretory transport were concentration dependent and saturable process (K(m) was 49.8 +/- 1.2 microM, V(max) was 38.28 +/- 0.8 ng/cm(2)/min). In the presence of verapamil (100 microM) and CsA (10 microM), potent inhibitors of P-glyprotein (P-gp)/MRP2 (cMOAT), the P(appBL-AP)/P(appAP-BL) ratio was decreased from 3.4 to 1.4 and 1.3, respectively, and permeation of apical to basolateral was enhanced approximately two-fold. In the everted gut sacs, the absorption of 9-NC was passive diffusion and had no significant difference in different gut regions. Adding verapamil in the everted gut sacs over a concentration ranging from 10 to 100 microM, the absorption of 9-NC was significantly enhanced, especially more markedly in lower small intestine (P < 0.05). Overall, the current study suggests that pH and efflux transporters are capable of mediating the absorption and efflux of 9-NC, and they may play significant roles in limiting the oral absorption of 9-NC.     

The absorption behavior of cyclosporin A lecithin vesicles in rat intestinal tissue

The purpose of the study was to investigate the absorption behavior of lecithin vesicles of cyclosporin A (CsA-VES), prepared by the rotary evaporation method and treated further with sonication. The everted gut sac technique and in situ circulation method were used to examine: (1) relationship between the CsA-VES absorption velocity and the CsA-VES content; (2) the influence of the intestinal mucus, blank vesicles, concentration of Na(+), energy inhibitor and P-gp inhibitor on the absorption of CsA-VES; and (3) the respective accumulated content of CsA in the incubating medium and the sacs after incubation with Sandimmum Neoral((R))(CsA-NEO) and CsA-VES. Our results showed there was a saturated absorption of CsA. Most CsA-VES accumulated in the mucus before it reached the intestinal tissue. There was no significant difference in the accumulated absorption content in the incubating medium and the sacs of CsA-NEO and CsA-VES. The addition of blank vesicles and concentration of Na(+) had no significant influence on the accumulated absorption of CsA (P>0.05).The energy inhibitor and P-gp inhibitor influenced the accumulated absorption of CsA significantly (P<0.05). CsA-VES may be transported by phagocytosis. Mucus was a barrier blocking the diffusion of CsA-VES. CsA-NEO and CsA-VES showed equal absorption levels in the intestine.     

Role of Intestinal First-Pass Metabolism of Baicalein in its Absorption Process

Purpose The aim of the present study was to investigate the role of intestinal first-pass metabolism of baicalein (B) in its absorption process.Methods The intestinal absorption of B was characterized using Caco-2 cell monolayer model and rat in situ single-pass intestinal perfusion model. In addition, preliminary metabolic kinetics of B was evaluated in both rat and human intestinal S9 fractions.Results B was well absorbed and extensively metabolized to baicalin (BG), baicalein-7-O-β-glucuronide, in rat intestinal perfusion model, whereas less extent of metabolism was observed in the Caco-2 cell monolayer model. Moreover, BG generated in the intestinal epithelium during the absorption of B also rapidly transported to both the apical side (the apical chamber of Caco-2 model and the perfusate of the intestinal perfusion model) as well as the basolateral side of the small intestine (the basal chamber of Caco-2 model and the mesenteric vein of the intestinal perfusion model). From the preliminary metabolic studies, it was found that a higher loading dose of B resulted in a less extent of metabolism in intestine. In addition, the extent of metabolism of B was similar in jejunum and ileum when 50 μM of B was perfused through different sections of rat small intestine.Conclusion The first-pass metabolism of B in small intestine may play an important role in its low oral bioavailability.     

Enhancing effect of N-octyl-O-sulfate chitosan on etoposide absorption

P-glycoprotein (P-gp), expressed in the apical membranes of the epithelial cells of the intestine, can reduce the oral bioavailability of a wide range of drugs. Many surfactants/excipients have been demonstrated to potentially increase drug absorption by inhibiting P-gp. The purpose of the present study was to evaluate the effect of N-octyl-O-sulfate chitosan (NOSC) on the absorption of etoposide (VP16), a substrate of P-gp with low water solubility. The rat intestinal circulating perfusion in situ and Caco-2 cell uptake and monolayer membrane penetration in vitro were performed to investigate the enhancing ability of NOSC in comparison with some other P-gp inhibitors. The results indicated that various concentrations of NOSC all increased the intestinal absorption of VP16 in rat jejunum and ileum obviously and there was no significant difference in ileum between the enhancing effects of NOSC and other P-gp inhibitors. The VP16 uptake of Caco-2 cell was increased by NOSC solution with different concentrations. As the NOSC concentration was close to its critical micelle concentration (CMC), the cell uptake of VP16 reached to a maximum value. Both NOSC and verapamil (Ver) enhanced dramatically the transport of VP16 from apical side to basolateral side in Caco-2 cell monolayers. Moreover, they both decreased notably the transport of VP16 from basolateral side to apical side, but this effect of NOSC was weaker than that of Ver. However, transepithelial electrical resistance (TEER) of Caco-2 cell monolayers had no significant change during the study. These studies demonstrated that NOSC had the potential by inhibiting P-gp to improve the absorption of oral drugs which were P-gp substrates.     

西替利嗪肠吸收机制研究

目的:考察西替利嗪在小肠的吸收特征.方法:采用离体肠外翻法,以HPLC法测定不同浓度西替利嗪在大鼠各肠段的吸收量,并分别计算吸收速率常数(Ka)和表观渗透系数.考察P-糖蛋白(P-gp)抑制剂地高辛和多药耐药相关蛋白-2(Mrp-2)抑制剂丙磺舒对西替利嗪肠吸收的影响.结果:西替利嗪在各肠段均有较好的吸收,Ka和表观渗透系数按空肠、十二指肠、结肠和回肠依次下降.各肠段累积吸收量与浓度呈非线性关系,高浓度时吸收加快.P-gp抑制剂地高辛使西替利嗪的吸收明显增加,而Mrp-2抑制剂丙磺舒对西替利嗪的肠吸收没有明显影响.结论:西替利嗪的转运受P-gp介导,临床应用中需注意P-gp及其底物对西替利嗪体内过程的影响.     

Inhibitory effect of fruit extracts on P-glycoprotein-related efflux carriers: an in-vitro screening

In this study, standardized food extracts were screened for their possible inhibitory effect on the P-glycoprotein (P-gp)-mediated efflux of 3H-ciclosporin A (CsA) using the in-vitro Caco-2 model. CsA is commonly used as a substrate for P-gp-related efflux carriers and is characterized by a polarity in transport, the absorptive transport being much lowerthan the secretorytransport (polarityfactor: PF approximately 7). Of the 68 tested, nine extracts showed a decreased efflux of CsA (< 75% of the reference value) and were retained for further experiments on the bidirectional transport of CsA across Caco-2 monolayers. Results of these experiments showed that strawberry, orange, apricot and mint extract exert an inhibitory effect on intestinal P-gp-related functionality (PF < 4.2). The effect of apricot extract was also studied on the bidirectional transport of talinolol, a specific P-gp substrate; inclusion of 1%, v/v, in the apical compartment of Caco-2 monolayers resulted in a significantly reduced polarity in the transport of talinolol (PF reference = 15.5; PF in the presence of apricot extract = 2.5). This study suggests that co-administration of fruit extracts might be a conceptually safe and useful strategy to enhance the intestinal absorption of P-gp substrates. More research is necessary to characterize the impact of this inhibition on P-gp-related efflux mechanisms in other absorption models (in-vitro and in-vivo) and to identify the compounds that are responsible for this inhibitory effect.