Bropirimine-Induced Embryolethality after Oral Administration to the Pregnant Rat

Oral bropirimine (an immunomodulator shown to induce interferon)was administered to timed-pregnant Sprague-Dawley rats in fiveexperiments utilizing several different dosing schedules. Concentrationsof 100, 200, and 400 mg/kg of bropirimine were used. Interferonlevels were determined in maternal serum, spleen, and wholeembryo extracts and uterine contents were evaluated for survivalof the embryos. Maternal toxicity occurred in all experimentsas evidenced by dose-related decreases in body weight duringthe first 24 hr postdosing. Hematoxicology analyses of maternalserum revealed significant decreases in urea nitrogen, potassium,and albumin, along with increases in aspartate transaminase,alanine transaminase, and total bilirubin, in bropirimine-treateddams as compared to the vehicle controls. In addition, the meansfor maternal thymus weight decreased while the means for spleenweight increased with increasing concentration of bropirimine.As compared to the vehicle controls, interferon titers werehigh in maternal serum, maternal spleen, and, to a lesser extent,whole embryos, 2 hr postdosing, but had decreased or were belowdetectable levels 24 hr postdosing. Embryolethality was pronounced(increases in pre- and postimplantational loss) after a singledose (Gestation Day 3, 4, 5, 8, 9, or 10) of bropirimine, aswell as after 7 or 8 consecutive days (Gestation Days 6–12or 6–13) of treatment. Although embryotoxicity never occurredin these experiments in the absence of pronounced maternal toxicity,the pregnant dams never died as the result of bropirimine treatment,whereas the embryos frequently failed to survive.     

Oral Absorption of Peptides Through the Cobalamin (Vitamin B12) Pathway in the Rat Intestine

Purpose. This study was aimed at examining the extent and mechanismof uptake of cobalamin (Cbl)-conjugated peptides in vitro and in vivo. Methods. To enable acquisition of quantitative absorption data ofCbl-peptides, metabolically stable octapeptides (DP3), with (Cbl-Hex-DP3)or without a hexyl spacer (Cbl-DP3), were coupled to Cbl andradiolabeled. For comparison, LHRH coupled to Cbl was used as metabolicallysusceptible peptide. Biological recognition of Cbl-peptides was studiedin the physiological order: binding by Intrinsic Factor (IF), recognitionand transport of the IF-complexes by IF-Cbl receptors (IFCR) onCaco-2 monolayers and oral absorption of the Cbl-conjugates in the rat. Results. All Cbl-peptides bound to IF and the IF-complexes wererecognized by IFCR receptors on Caco-2 monolayers. Binding wassaturable and could be inhibited by a 20-fold excess of IF-Cbl, but notof Non-intrinsic Factor (NIF)-Cbl. Oral administration of these ligandsto rats resulted in absorption of 53%, 45%, 42%, and 23% of theapplied radioactivity for Cbl, Cbl-LHRH, Cbl-Hex-DP3, and Cbl-DP3,respectively. Simultaneous administration of a >10⁵-fold excess ofunlabeled Cbl reduced uptake of all compounds to <4%. Tissuedistribution and elimination of the metabolically stable Cbl-conjugates werecomparable to Cbl. Conclusions. The endogenous Cbl uptake pathway can be exploitedfor oral peptide delivery as indicated by the specific and high (40–45%)uptake of metabolically stable Cbl-coupled octapeptides.Deceased     

槲皮素纳米乳大鼠在体小肠吸收动力学

目的研究槲皮素纳米乳在大鼠体内各肠段的吸收情况,并考察其形态学及粒径分布.方法采用大鼠在体小肠各段回流实验,紫外分光光度法测定药物浓度,根据药物在小肠各段中的减少量来确定药物的吸收;采用透射电子显微镜观察纳米乳形态.结果槲皮素纳米乳在大鼠十二指肠、空肠、回肠及结肠中的吸收速率常数(ka)依次为0.0675,0.1056,0.1892,0.1615 h-1;透射电镜下槲皮素纳米乳呈球形,大小均匀,平均粒径(16.3±4.6)nm;结论槲皮素纳米乳在小肠下段吸收较好,吸收呈一级动力学过程.     

Absorption of Organic Anions from the Rat Small Intestine

Abstract

1. Hippuric acid, sulphanilic acid, p-aminohippuric acid, and phenol red, highly ionized compounds of very low lipoid solubilities, were absorbed from the rat small intestine at rates which varied over a 25-fold range.

2. Absorption rates ranked in the same order as the chloroform-to-water partition coefficients of the compounds but not in the order of the molecular weights or degrees of ionization.

3. The results suggested that these anions are absorbed mainly by simple diffusion through lipoid regions of the intestinal boundary.     

Stability of Bovine Lactoferrin in Luminal Extracts and Mucosal Homogenates from Rat Intestine: A Prelude to Oral Absorption

Oral delivery is the most common method for bovine lactoferrin (bLf) administration. However, the presence of proteolytic enzymes in the stomach and intestine limits the effective absorption of bLf within the gastrointestinal (GI) tract. To determine the extent of bLf proteolysis, several digestion models were developed using luminal extracts and mucosal homogenates isolated from four regions of rat intestine: duodenum, jejunum, ileum, and proximal colon. The kinetics of bLf degradation followed a pseudo‐first‐order rate, and almost complete hydrolysis of bLf was observed in the luminal extracts, indicating that bLf is more susceptive to luminal peptidases rather than mucosal enzymes. Moreover, a significant reduction in bLf proteolysis was observed in the presence of soybean trypsin inhibitor (SBTI), bestatin, and bacitracin, suggesting that there exist trypsin‐like and aminopeptidase‐like proteases, which play a key role in the degradation of bLf in the intestine. Lactoferrin was then encapsulated in several lipid‐based delivery systems including liposomes and solid lipid particles (SLPs) with polymer modification, showing at least 50% of intact bLf remaining after 6 h of digestion compared with native bLf. These findings suggest that particle encapsulation may modulate protein digestion and possibly achieve sufficient oral bioavailability of bLf.     

Absorption of Organic Arsenical Compounds from the Rat Small Intestine

Abstract

1. The pentavalent organic arsenical compounds carbarsone, tryparsamide, and cacodylic acid were absorbed from the rat small intestine at rates directly proportional to concentration over a 100-fold range.

2. Absorption half-times (min) were: carbarsone, 87; tryparsamide, 184; and cacodylic acid, 201.

3. Absorption rates (first-order rate constants) ranked in the same order as the CHCl₃-to-water partition coefficients of the compounds as measured at pH 5·3.

4. The results suggested that these organo-metallic compounds are absorbed mainly by a process of simple diffusion.     

Effects of Calcium on Cadmium Uptake and Binding in the Rat Intestine

Effects of Calcium on Cadmium Uptake and Binding in the RatIntestine. HOADLEY, J. E., AND JOHNSON, D. R. (1987). Fundam.Appl. Toxicol. 9, 1–9. Cadmium uptake in vitro was evaluatedin everted duodenal, jejunal, and ileal segments of the ratsmall intestine. Washing the sacs with EDTA subsequent to cadmiumexposure distinguished labile and nonlabile cadmium compartments.These compartments were distinct with respect to regional distribution,kinetics, and effect of calcium. Uptake into the nonlabile cadmiumcompartment but not into the labile cadmium compartment wastime dependent, consistent with transport and adsorption processes,respectively. Initial uptake rates for the nonlabile cadmiumcompartment showed both saturable and first-order kinetics.Calcium inhibited only the saturable mechanism. Cadmium uptakerate and sensitivity to calcium were greatest in the duodenumdue to the predominance of the saturable mechanism in this region.Distal to the duodenum cadmium uptake exhibited primarily first-orderkinetics. The V_max for the saturable process was reduced 90%by calcium. The absence of competitive inhibition indicatesthat calcium and cadmium do not share a common carrier-mediateduptake mechanism. The amount of cadmium bound in the labilecompartment was comparable in all segments and could be describedby a nonlinear function which was the sum of the saturable andsecond-order terms. Addition of calcium had an apparent cooperativeeffect on cadmium binding, increasing the second-order termof binding in the labile compartment. Thus calcium was foundto have a dual effect on cadmium accumulation by intestinaltissue: inhibition of saturable duodenal uptake and stimulationof binding throughout the small intestine.     

大鼠口服茯苓素后血浆中的去氢土莫酸药代动力学研究

目的:建立测定大鼠血浆中去氢土奠酸浓度的高效液相色谱方法,并以去氢土莫酸为指标,研究大鼠灌胃给予茯苓素混合提取物后的药代动力学行为。方法:采用HPLC方法测定大鼠灌胃给予茯苓素混合提取物后,血浆中去氢土莫酸的浓度。色谱柱为ODS枉(200mm×4.6 mm,5μm),流动相为甲醇乙腈-2％冰醋酸水溶液(13:12:10),流速为1.0mL·min~(-1),检测波长为242nm,进样量20μL,室温下操作,内标物为丙酸睾丸素。结果:在0.20～20.0μg·mL~(-1)范围内具有良好线性关系(r=0.9981),方法回收率为85.2％～93.6％,日内、日间RSD均小于6.0％,达峰时间约为2h,峰浓度为(10.4±1.4)μg·mL~(-1),药时曲线下面积为32.6μg·mL~(-1)·h~(-1)。结论:此方法稳定、可靠,适用于茯苓素的药代动力学研究。     

Effect of Iron on the Absorption and Distribution of Clodronate after Oral Administration in Rats

The effect of iron on the absorption and distribution of disodium clodronate in rats after oral administration was studied. Disodium clodronate (300 mg/25 μCi/kg) was given both alone and with an equivalent amount of ferrous sulphate. The radioactivity in plasma and various tissue was measured. Concentration of clodronate in plasma was also determined with the GC-mass-selective detection method and the values compared with those measured with the isotope method. After administration, clodronate was rapidly cleared from plasma. Most of the dose was taken up by bone and only small amounts were found in non-calcified tissues. Concurrent ingestion of iron caused a marked decrease in the absorption of clodronate.     

阳离子纳米乳提高替尼泊苷口服吸收的研究

采用表面活性剂聚乙二醇1000维生素E琥珀酸酯(TPGS)、聚乙二醇十二羟基硬脂酸酯(HS-15),阳离子脂质十八胺及中链甘油三酯(MCT),以分子自组装技术制备替尼泊苷阳离子纳米乳.所得制品平均粒径为(61.9±4.5) nm,ζ电位为(+8.38±3.34)mV.体外细胞毒性试验显示,本品能显著提高替尼泊苷对人肺癌细胞A549的杀伤作用.与替尼泊苷溶液相比,本品能显著提高替尼泊苷在小鼠肠道及心、肝、脾、肺和肾中的分布.大鼠体内药动学研究表明,本品可显著提高替尼泊苷的峰浓度及AUC,口服相对生物利用度是溶液组的380％.     

Enhanced Oral Uptake of Tomato Lectin-Conjugated Nanoparticles in the Rat

Purpose. To investigate the usefulness of a surface-conjugated, bioadhesive molecule, tomato lectin, to augment intestinal uptake of orally administered inert nanoparticles. Methods. Fluorescent 500 nm polystyrene nanoparticles with tomato lectin covalently surface coupled using a carbodiimide reaction were administered to female Wistar rats by oral gavage daily for 5 days. Results. Analysis of tissue extracted polymer by gel permeation chromatography revealed a 23% systemic uptake of tomato lectin conjugated nanoparticles compared to < 0.5% of TL nanoparticles blocked with N-acetylchitotetraose thus representing an increase of almost 50 fold across the intestine. Intestinal uptake of tomato lectin-conjugated nanoparticles via the villous tissue was 15 times higher than uptake by the gut-associated lymphoid tissue. Conclusions. The application of tomato lectin as a bioadhesive agent in vivo has been demonstrated to enhance subsequent intestinal transcytosis of colloidal particulates to which it is bound.Deceased December 2, 1995.     

Regulation of Paracellular Absorption of Cimetidine and 5-Aminosalicylate in Rat Intestine

Purpose. Isolating the relative contributions of parallel transcellular and paracellular transport to the intestinal absorption of small hydrophilic molecules has proven experimentally challenging. In this report, lumenal appearance of drug metabolite is utilized as a tool to assess the contribution of paracellular transport to the absorption of cimetidine and 5-aminosalicylate (5ASA) in rat small intestine. Methods. Steady-state intestinal absorption and elimination of cimetidine and 5ASA were studied in single-pass intestinal perfusions in rats. Results. Both drugs were metabolized in intestinal epithelia with subsequent metabolite secretion into the intestinal lumen. Jejunal cimetidine absorption decreased with increasing perfusion concentration while the ratio of lumenal metabolite to lumenal drug loss increased. Cimetidine uptake at perfusion concentrations above 0.4 mM resulted in over 80% drug elimination into the jejunal lumen. Inhibition of intracellular metabolism of cimetidine by methimazole did not alter epithelial uptake but totally abolished transepithelial cimetidine flux indicating an elevation of intracellular cimetidine. Similarly, co-perfusion of 5ASA with cimetidine and methimazole totally abolished 5ASA absorption but increased lumenal levels of N-acetyl 5ASA indicating an increase in intracellular uptake of 5ASA. Conclusions. Cimetidine and 5ASA absorption across rat jejunal epithelia are exclusively paracellular. Elevation of intracellular cimetidine, inferred from mass balance considerations, restricts paracellular transport of both drugs.     

诺模图法预测口服给药的吸收速率常数

目的：用已知的达峰时间(tpeak)和消除速率常数(ke)建立诺模法，估算口服给药的吸收速率常数(ka)。方法：根据口服给药的血药浓度—时间曲线曲线方程和tpeak,ka和ke的函数关系，进行数学推导建立诺模图。应用诺模图分析46个药物的ka与数学解析法计算的ka，比较评价诺模图的准确度。用高效液相色谱荧光法检测18位健康志愿者羧甲司坦的血药浓度，将羧甲司坦实测血药浓度与由ka结合其他药代动力学参数的估计血药浓度比较，评估诺模图执行误差。结果：诺模图估算的ka值与解析法计算的ka值接近；MDPE和MDAPE执行误差分别为1．32％，18．15％。结论：本文设计的诺模图准确可靠，执行误差符合临床药代动力学要求。可为制定合理的个体化给药方案提供一个方便快捷的方法。     

五酯胶囊对环孢素在大鼠小肠吸收的影响

目的：研究五酯胶囊（WuZhi—capsule，WZ）对环孢素（cyclosporinA，CsA）在大鼠小肠吸收的影响。方法：三组大鼠分别以CsA试液、含WZ100mg&#183;L^-1的CsA试液、含WZ200mg&#183;L^-1的CsA试液进行在体肠段吸收实验，HPLC法测定CsA浓度。结果：与单用CsA相比，回肠段合用WZ组CsA吸收率明显降低，空肠段合用WZ组CsA吸收无明显变化。结论：WZ对CsA小肠吸收有抑制作用。     

Drug Absorption from the Small Intestine of the Triparanol–Treated Rat in Situ

Abstract The effect of treatment with triparanol (25 mg/kg by gavage every 24 hours for three weeks) on the absorption of phenobarbitone, sulphafurazole, isoniazid, mecamylamine and quinidine from the rat small intestine was studied in situ by measuring their disappearance from the intestinal lumen. The appearance of sulphafurazole and mecamylamine in the intestinal lumen was also studied after their intravenous administration, and the partitioning of mecamylamine between the buffer solution and the intestinal tissue was measured in vitro. Treatment with triparanol retarded the absorption of sulphafurazole, whereas the absorption of mecamylamine was accelerated. The amount of sulphafurazole and mecamylamine in the intestinal lumen after their intravenous administration was relatively slight. The in vitro partitioning of mecamylamine into the intestinal tissue was higher in triparanol–treated than in control intestines. Triparanol did not change the absorption of phenobarbitone, isoniazid or quinidine. Phenobarbitone in the whole blood at the end of the experiment was increased after triparanol, but the levels of other drugs were unchanged. Triparanol did not modify drug concentrations in the intestinal wall at the end of the experiment. The relatively slight changes in drug absorption induced by triparanol are probably due to changes in the morphology and composition of the intestinal wall.     

The Transfer of Polystyrene Microspheres from the Gastrointestinal Tract to the Circulation after Oral Administration in the Rat

Factors relating to the transfer of latex microspheres of 0·87 μm mean diameter from the gastrointestinal tract (GIT) to the circulation have been investigated. The rapidity of appearance and the number of particles increased when the volume of water used as a suspending vehicle was increased. This was probably due to barrier cell integrity being compromised so that the movement of particles across the enterocytes would be enhanced. Particles were swept into these channels by the waterflow. The tonicity of the fluid was important as isotonic and hypertonic saline were not as affective as water in transferring particles. Particles were transferred from GIT segments adjacent to the stomach which may in part explain the rapid appearance of particles in the circulation. Particle uptake was blocked by cytochalasin B which suggests an active component may also be involved.     

Absorption and Bioavailability of Diclofenac after Rectal Administration of Diclofenac-Na Gel Preparation in Rat and Man

In order to evaluate diclofenac-Na (DC-Na) micro-enema, DC-Na gel preparations were administered to rats and man. When DC-Na gel preparations were rectally administered at various pH (pH 5– 8) to rats, their bioavailability increased at higher pH. The bioavailability of DC-Na gel preparations (pH 8.0) in rats was significantly higher than that with conventional suppository bases, Witepsol H-15 and polyethylene glycol 1000 (PEG 1000). In man, the DC-Na gel preparation showed higher C_max and higher bioavailability than commercial suppository made with an oily base. DC-Na gel preparations containing 10% v/v oleic acid showed a prolonged action. The irritative effect of DC-Na gel preparation on rectal mucosa in rats was weaker than that of PEG 1000, but similar to that of Witepsol H-15. Therefore, the present results suggest that gel preparation is a favorable form for rectal administration of diclofenac-Na.     

In Vivo Absorption of Theophylline and Salicylic Acid from Rat Small Intestine

Abstract: In vivo absorption of theophylline and salicylic acid from the rat small intestine was studied by a closed segment technique. The drugs were administered at 1 and 4 mM in dissolved form, both in the presence and absence of phlorizin (0.01 mM). Drug concentrations were measured by high-pressure liquid chromatography. Phlorizin inhibited the absorption of theophylline (pK_a = 8.6) at 4 mM but not at 1 mM. In contrast, the absorption of salicylic acid (pK_a = 3) both at I and 4 mM was unaffected by phlorizin. This suggests that an active transport system, sensitive to phlorizin, is involved in the rat intestinal absorption of theophylline, but not in that of salicylic acid. Apart from differences in drug structure, differences in the degree of ionization may influence the access of acidic drugs to this transport system.     

Biopharmaceutics: Cytotoxicity of Absorption Enhancers in Caco-2 Cell Monolayers

This study was performed to evaluate the utility of absorption enhancers with reference to mucosal cell cytotoxicity. Overall assessment of the damage to plasma, lysosomal and nuclear membranes by three absorption enhancers, sodium deoxycholate, sodium caprate and dipotassium glycyrrhizinate, was performed on Caco-2 cell monolayers. The cytotoxicities of sodium deoxycholate (0.02–0.1% w/v), sodium caprate (0.1–0.5% w/v) and dipotassium glycyrrhizinate (0.5–2% w/v) were evaluated by the trypan blue-exclusion test, the protein-release test, the neutral-red assay, the DNA-propidium iodide staining test and the test for recovery of transepithelial electrical resistance (TEER) up to 24 h after treatment with each enhancer. Sodium dodecyl sulphate (SDS; 0.1% w/v), a potent surfactant, was used as positive control. SDS at this level was significantly cytotoxic whereas dipotassium glycyrrhizinate was not cytotoxic in any tests. Results from the trypan blue-exclusion and protein-release tests showed that high concentrations of sodium caprate (0.5% w/v) and sodium deoxycholate (0.1% w/v) were significantly cytotoxic to the plasma membrane. The neutral-red assay, an indicator of damage to lysosomal membranes, revealed that 0.5% (w/v) sodium caprate had no effect whereas the uptake of neutral red was slightly increased by treatment with 0.1% (w/v) sodium deoxycholate, implying that the compound had cell-growth-enhancing activity. Nuclear-membrane damage, as evaluated by the DNA-propidium iodide staining test, was severe in cell monolayers treated with 0.5% (w/v) sodium caprate compared with that induced by 0.1% (w/v) sodium deoxycholate. In the TEER recovery test, TEER failed to recover 24 h after treatment with 0.5% (w/v) sodium caprate and 0.1% (w/v) SDS, but recovered after treatment with 0.1% (w/v) sodium deoxycholate. The recovery of TEER might be related to nuclear membrane damage and cell-growth-enhancing activity. These results indicate that of the three classes of enhancer, dipotassium glycyrrhizinate was not cytotoxic and that high concentrations of sodium caprate and sodium deoxycholate could damage plasma and nuclear membranes.