中空纤维液相微萃取结合高效液相色谱法测定比索洛尔血浆蛋白结合率

目的将中空纤维液相微萃取技术与高效液相色谱法结合,建立测定比索洛尔血浆蛋白结合率的新方法。方法优化比索洛尔血浆样本的液相微萃取条件;利用高效液相色谱法测定比索洛尔在接受相中的浓度,色谱条件为水-甲醇-乙腈-0.1%磷酸(50∶34∶6∶10),检测波长Ex:232 nm,Em:300 nm,分别代入当日标准曲线计算出比索洛尔血浆游离药物浓度及总药物浓度,进而计算比索洛尔血浆蛋白结合率。结果在低、中、高3种浓度下测得比索洛尔的血浆蛋白结合率分别为31.2%,32.0%,31.8%。结论所建立的方法简便快速,重复性好,适用于药物游离浓度及血浆蛋白结合率的测定。比索洛尔与人血浆蛋白有中等程度结合,且不存在浓度依赖性。     

吗啡游离浓度测定及人血红蛋白结合研究

目的　建立人血红蛋白溶液中吗啡游离浓度测定方法 ,了解吗啡与血红蛋白的结合率 ,计算相关参数。方法　采用超滤法分离出游离吗啡 ,高效液相色谱法测定游离吗啡浓度 ,以总浓度减去游离浓度的差值与总浓度的比值为吗啡-血红蛋白结合率。结果　吗啡的超滤平均回收率为98 5 % ,测定的精密度为 1 1%～ 1 5 %。在体外 ,吗啡总浓度在 8 5 0× 10 -5～ 1 17× 10 -2 mol·L-1、人血红蛋白浓度在1 2 9× 10 -4～ 8 5 7× 10 -4mol·L-1范围内 ,吗啡与人血红蛋白具单一类型结合部位 ,吗啡 -血红蛋白结合参数 :人血红蛋白结合部位数 (N)为 4 1,吗啡 -血红蛋白结合常数 (K)为 30 4L·mol-1。结论　超滤法结合高效液相色谱法是一种简便、快速的游离药物浓度测定方法 ,适用于药物蛋白结合率试验研究。在体外 ,吗啡与血红蛋白结合率随吗啡与血红蛋白浓度变化     

替加色罗大鼠血浆蛋白的结合率测定

目的 测定大鼠血浆蛋白结合率。方法 血浆样品加入内标后用乙酸乙酯提取,进行HPLC分析。采用平衡透析法测定大鼠血浆中替加色罗的血浆蛋白结合率。结果 替加色罗浓度在42.51～235.73 ng·ml^-1范围内,药物血浆蛋白结合呈线性关系,替加色罗与大鼠血浆蛋白结合率为92.4%。结论 替加色罗与大鼠血浆蛋白结合率较高。     

银杏内酯B在血浆中的蛋白结合率研究

目的测定银杏内酯B(ginkgolide B,GB)与大鼠和人的血浆蛋白结合率。方法将血浆样品加入内标23-羟基白桦酸,乙醚液液萃取后,高效液相色谱-质谱联用仪分析,采用平衡透析法测定GB在大鼠及人血浆中的血浆蛋白结合率。结果人和大鼠血浆中GB药物浓度在0.05～5.00 mg.L-1范围内血浆蛋白结合呈线性关系;GB与大鼠血浆蛋白结合率约为25%,与人血浆蛋白结合率约为20%。结论 GB的血浆蛋白结合率较低,在人血浆的蛋白结合率略低于大鼠,但不存在显著性差异;约80%的药物以游离态形式存在。     

TJ0711盐酸盐的血浆蛋白结合率及其在大鼠体内的组织分布

目的:建立生物样品中TJ0711盐酸盐的浓度的测定方法,测定TJ0711盐酸盐在人标准血浆和大鼠血浆中的蛋白结合率,考察其在大鼠组织中的分布特性。方法:用平衡透析法测定血浆蛋白结合率,用高效液相-荧光检测法测定血浆中药物总浓度及游离药物浓度。大鼠灌胃给予TJ0711盐酸盐30 mg.kg-1,测定10,25,60,180 min TJ0711盐酸盐在各组织中的含量。结果:当TJ0711盐酸盐的血药浓度为0.5,2.0,4.0,8.0μg.mL-1时,其在大鼠血浆中的蛋白结合率分别为(88.7±2.3)%,(87.8±1.0)%,(85.8±2.0)%和(86.8±0.9)%,在人血浆中的蛋白结合率分别为(92.1±0.8)%,(89.8±1.4)%,(90.4±1.0)%和(90.4±1.7)%。药物在大鼠体内以肾、肝、肺中分布较多,脑和脂肪组织也能检测到药物,绝大多数组织的药物含量在给药后10 min或25 min最高1,80 min后药物含量显著下降。结论:TJ0711盐酸盐在人和大鼠血浆中的蛋白结合率均属于高度结合(>80%),且不随药物浓度的增加发生变化,但在人和大鼠血浆中的蛋白结合率差异具有显著性(...     

毒鼠强人血浆蛋白结合率的研究

目的 建立人标准血浆中毒鼠强浓度的GC/NPD测定法,测定毒鼠强人血浆蛋白结合率.方法 用平衡透析法测定血浆蛋白结合率,用GC/NPD测定法测定血浆侧毒鼠强浓度.结果 正常人血浆中毒鼠强浓度在100ng/ml、300ng/ml、500ng/ml时的蛋白结合率在12.62%～15.41%之间.结论 毒鼠强与人血浆蛋白率较低,属低度结合,对临床现象的解释有重要意义.     

高效液相色谱法测定布洛芬与人血浆蛋白的结合率

目的:建立人血浆中布洛芬浓度的测定方法,测定布洛芬在人血浆中的蛋白结合率,并计算相关参数。方法:用平衡透析法以高效液相色谱法为检测手段测定血浆蛋白结合率。结果:布洛芬与人标准血浆的蛋白结合率为(95.4±0.3)%。结论:布洛芬与人血浆蛋白为高强度结合。     

氯化两面针碱与兔血浆的蛋白结合率研究

目的:测定氯化两面针碱与兔血浆蛋白的结合率。方法:通过平衡透析法结合高效液相色谱法测定氯化两面针碱与兔血浆蛋白的结合率。结果:氯化两面针碱与内标(氯霉素)完全分离,血浆中其它成分无干扰;其在0.03188～2.04000μg·mL-1浓度范围内与氯化两面针碱同氯霉素峰面积比线性关系良好;0.125、0.25、0.5μg·mL-1浓度样品的方法回收率均>95%,日内、日间精密度的RSD均<5%;3种药物浓度的血浆蛋白结合率分别为73.21%、72.83%、70.30%。结论:氯化两面针碱与兔血浆蛋白具有中等强度的蛋白结合率。     

高效液相色谱法测定间尼索地平不同对映体在血浆中的蛋白结合率

目的:建立间尼索地平不同对映体在大鼠血浆、人血浆和牛血清白蛋白中蛋白结合率的测定方法,并计算不同种属血浆蛋白的相关参数。方法:采用平衡透析法测定蛋白结合率,用高效液相色谱法测定血浆中药物总浓度及游离药物浓度。结果:R-与S-间尼索地平的血浆蛋白结合率分别为:大鼠血浆为(97.4±8.2)%、(93.0±13.4)%;人血浆为(90.8±10.5)%、(89.2±9.9)%;牛血清白蛋白为(95.3±8.7)%、(91.0±5.7)%。最低定量下限为0.01ng。结论:在体外间尼索地平不同对映体与大鼠血浆、人血浆和牛血清白蛋白结合率很高,R-间尼索地平的结合率及蛋白结合药物的表观最大能力βp均较S-间尼索地平高。随着药物血浆浓度升高,R-间尼索地平结合率下降,S-间尼索地平结合率升高,均有一定的浓度依赖性。     

氯化两面针碱人血浆蛋白结合率的测定

目的建立测定人血浆中氯化两面针碱的高效液相色谱法,并研究氯化两面针碱与人血浆蛋白的结合情况。方法离子对试剂萃取技术对样品进行预处理,乙腈-0.15%磷酸(36:64,V:V,用三乙胺调pH值至3.5)为流动相,C_(18)柱(250mm×4.6mm,5μm)为固定相,紫外检测波长271nm,以氯霉素为内标,采用平衡透析法对氯化两面针碱的人血浆蛋白结合率进行测定。结果氯化两面针碱与内标完全分离,样品中其他成份无干扰,在0.03188～2.040mg·L~(-1)范围内线性关系良好,低、中、高3种不同质量浓度的方法回收率>95%,日内、日间精密度均符合方法学要求。低、中、高3种药物浓度的血浆蛋白结合率分别为68.9%、67.4%、67.9%。结论方法简便、快速,结果准确、可靠,能满足生物样品分析要求。氯化两面针碱具有中等强度的蛋白结合率,蛋白结合率与透析液的药物浓度无关。     

Interindividual Differences in the Protein Binding of Sulfonamides: The Effect of Disease and Drugs 1,2

Abstract: The variation in the plasma protein binding of sulfonamides in healthy adults was minimal. Additional evidence for consistency in binding came from a literature survey in which it was found that the plasma protein binding of several sulfonamides in man and laboratory animals was remarkably similar as reported by investigators from different countries. Some hospitalized patients, however, do show a binding deficiency which may be due to an interaction between drugs, disease and altered plasma proteins. Several drugs were found to compete with the sulfonamide for the same binding sites on the protein (albumin) molecule. The plasma protein binding of a sulfonamide in six anephric patients was studied before and after haemodialysis. As expected all showed a deficiency in binding. Unexpectedly, however, the binding was less in the post-dialysis plasma sample in three patients. In some patients there appeared to be a qualitative and a quantitative change in the binding sites on the protein. More definitive studies are needed with plasma protein fractions from healthy and ill subjects in the presence and absence of drugs. This may lead to a better understanding of the side effects to some drugs and could result in the development of useful displacing agents.     

The use of nonhomologous Scatchard analysis in the evaluation of ligand–protein interactions

Scatchard plots are widely used for the graphical presentation of receptor–ligand binding data. When a combination of labelled and unlabelled ligand molecules is used in a binding assay, equations for Scatchard plots are readily available if the labelled and unlabelled ligands have similar binding affinities. In this article, Everardus van Zoelen, Roel Kramer, Herman van Moerkerk and Jacques Veerkamp present mathematical equations to obtain the binding characteristics of an unlabelled ligand in a Scatchard plot, which has a dissociation equilibrium constant different from that of the labelled ligand used.     

Serum Albumin - A Non-Saturable Carrier

Abstract: The shape of binding isotherms for sixteen ligands to human serum albumin showed no signs of approaching saturation at high ligand concentrations. It is suggested that ligand binding to serum albumin is essentially different from saturable binding of substrates to enzymes, of oxygen to haemoglobin, etc. Binding to serum albumin appears to be non-saturable.     

Docetaxel serum protein binding with high affinity to alpha1-acid glycoprotein

Summary The binding of docetaxel to human plasma proteins was studied by ultrafiltration at 37°C and pH 7.4. Docetaxel was extensively (> 98%) plasma protein bound. At clinically relevant concentrations (1–5 g/ml), the plasma binding was concentration-independent. Lipoproteins, alpha₁-acid glycoprotein and albumin were the main carriers of docetaxel in plasma, and owing to the high interindividual variability of alpha₁-acid glycoprotein plasma concentration, particularly in cancer, it was concluded that alpha₁-acid glycoprotein should be the main determinant of docetaxel plasma binding variability. Drugs potentially coadministered with docetaxel (cisplatin, dexamethasone, doxorubicin, etoposide, vinblastine) did not modify the plasma binding of docetaxel. In blood, docetaxel was found to be mainly located in the plasma compartment (less than 15% associated to erythrocytes).     

Characterization of salicylate binding to synovial fluid and plasma protein in patients with rheumatoid arthritis

Summary Protein binding of salicylate in synovial fluid and plasma from patients with rheumatoid arthritis was studied by equilibrium dialysis. Protein binding in the synovial fluid was considerably lower at all salicylate concentrations studied (0.07 – 2.2 mM). Scatchard plots of the data were analyzed assuming binding to two classes of binding sites, each plasma sample being diluted to an albumin concentration equal to that in synovial fluid from the same patient. Binding to the primary binding sites was considerably decreased in synovial fluid in comparison with plasma. The affinity of the secondary binding sites was slightly lower. Thus, at a low therapeutic drug concentration, the decreased binding of salicylate to synovial fluid protein in patients with rheumatoid arthritis could mainly be accounted for by decreasing affinity of binding to the primary binding sites.     

Effect of Competing Anions on Binding of Bile Salts by Cholestyramine

The binding of bile salts by cholestyramine may be influenced by other anions, as the Langmuir adsorption coefficients for three bile salts tested were similar to the model anion, citrate. However, the selectivity coefficient indicated preferential binding of cholate anion in comparison to citrate anion. Binding experiments confirmed cholestyramine's preference for bile salts as the presence of other anions reduced but did not prevent the binding of cholate anion. Binding of cholate anion was reduced in direct relationship to the citrate anion concentration. Prior exposure of cholestyramine to citrate anion caused the binding of cholate anion to decrease slightly. Sequential exposure of cholestyramine to simulated gastric fluid and simulated intestinal fluid containing cholate anion resulted in a decrease in cholate binding which was attributed to competition with anions present in the gastrointestinal fluids. Components of tomato juice and orange juice, fluids commonly used to enhance ingestion of cholestyramine, also reduced the binding of cholate anion.     

Radiolabeling of dopamine uptake sites in mouse striatum: comparison of binding sites for cocaine,mazindol, and GBR 12935

Summary This study addressed the possibility of a unique binding interaction between cocaine and the dopamine transporter as compared with other blockers of dopamine uptake. Cocaine binding sites in a fresh P₂ fraction of mouse striatum were labeled with [³H]CFT, a phenyltropane analog of cocaine also known as WIN 35,428, and compared with sites labeled with [³H]mazindol or [³H]GBR 12935. Under the conditions used, homogeneous binding was observed that was inhibited monophasically by cocaine, CFT, and mazindol; the same potencies were observed with the three radioligands. Saturation analysis in the presence and in the absence of unlabeled inhibitor (CFT, mazindol, cocaine) indicated a change in the K_d but not the B_max, consonant with a competitive mechanism. Tris-HCl reduced the affinity of each radioligand and unlabeled inhibitor without changing the B_max. N-Ethylmaleimide reduced the binding of all radioligands equally and cocaine offered protection. The dissociation rate of [³H]CFT and [³H]mazindol binding was not affected by the presence of mazindol and CFT, respectively. The B_max of [³H]CFT and [³H]mazindol binding was the same; the relatively higher value for [³H]GBR 12935 binding in analyses involving varying tritiated GBR 12935 only, was due primarily to an underestimation of the specific activity of [³H]GBR 12935. All results are in agreement with a one-site model in which cocaine, CFT, mazindol, and GBR 12935 share a common binding site in mouse striatum.     

Generalized pharmacokinetic modeling for drugs with nonlinear binding: I. Theoretical framework

The following integrodifferential equation is proposed as the basis for a generalized treatment of pharmacokinetic systems in which nonlinear binding occurs $$\phi '(c_u )c'_u = - q(c_u ) + g*c_u + f$$ where c_u≡unbound plasma drug concentration, f≡drug input rate,'indicates the derivative of a function, and * indicates the convolution operation: (g* c_u)(t)=∫ ₀ ^t g(t?u)c_udu.Possible physical interpretations of the functions q, g and f are: q (c_u)≡ rate at which drug leaves the sampling compartment, g * c_u ≡ rate at which drug returns to the sampling compartment from the peripheral system (tissues that are kinetically distinct from the sampling compartment), and φ(c_u) ≡ amount of drug in the sampling compartment. The approach assumes that drug binding is sufficiently rapid that it may be treated as an equilibrium process. It may be applied to systems in which nonlinear binding occurs within the sampling compartment, i.e., in the systemic circulation or in tissues to which drug is rapidly distributed. The proposed relationship is a generalization of most existing models for drugs with nonlinear binding. It can serve as a general theoretical framework for such models or as the basis for “model-independent” methods for analyzing the pharmacokinetics of drugs with nonlinear binding. Computer programs for the numerical solution of the integrodifferential equation are presented. Methods for pharmacokinetic system characterization, prediction and bioavailability are presented and demonstrated.     

Accumulation kinetics of drugs with nonlinear plasma protein and tissue binding characteristics

The purpose of this investigation was to study, by digital computer simulation, the accumulation kinetics of drugs which exhibit concentration-dependent binding to tissues and either linear (constant free fraction) or concentration-dependent (increasing free fraction with increasing drug concentration) binding to plasma proteins. It was assumed that elimination rate is proportional to free drug concentration in plasma and that there occurs instantaneous equilibration of drug between vascular and nonvascular spaces. Nonlinear binding can yield, under certain conditions, apparently biexponential plasma concentrationtime curves which may be misinterpreted as being representative of a linear and biexponential-system. Such misinterpretation would cause the following errors in the prediction of drug accumulation and elimination kinetics during and after constantrate infusion: (a) the time required to reach steady state may be overestimated, and (b) the prominence of the apparent distribution phase after cessation of infusion may be underestimated. Drugs with linear and nonlinear plasma protein binding characteristics differ with respect to the relationship between infusion rate and steadystate concentration. This relationship is linear when plasma protein binding is linear. Steadystate concentration increases less than proportionally with increasing infusion rate if plasma protein binding is drug concentration dependent.     

The Determination of Naproxen by Spectrofluorometry and its Binding to Serum Proteins

Abstract A fluorometric method for the determination of naproxen in serum, albumin solutions and protein free buffer solutions is described. The detection limit is about 10 ng/ml. Furosemide, thiopental and salicylic acid did not show any disturbing fluorescence while phenprocoumon did. The in vitro binding of naproxen in albumin solutions and serum was studied by equilibrium dialysis. A small but significant increase was found in the percentual binding in albumin solutions as compared to serum. The percentual binding was not affected by changes in the pH from 5-8. By fitting the binding data to a model assuming two classes of binding sites, association constants and binding capacities were determined. A very high affinity and a high capacity were found. The association constant for the first class of binding sites was higher for human serum albumin than for Serum (8.5 versus 5.3 · 10⁶ M^-1). The difference in the protein binding to the first class of binding sites in human serum albumin and serum can be explained by the existence of a competitive inhibitor in serum.