Activity and polymorphisms of butyrylcholinesterase in a Polish population

Butyrylcholinesterase (BChE) activity assay and inhibitor phenotyping can help to identify individuals at risk of prolonged paralysis following the administration of neuromuscular blocking agents, like succinylcholine, pesticides and nerve agents. In this study, the activity of BChE and its sensitivity to inhibition by dibucaine and fluoride was evaluated in 1200 Polish healthy individuals. In addition, molecular analysis of all exons, exon-intron boundaries and the 3'UTR sequence of the BCHE gene was performed in a group of 72 subjects with abnormal BChE activity (<2000 U/L and >5745 U/L) or with DN (Dibucaine Number) or FN (Fluoride-Number) values outside the reference range (DN < 78 and FN < lower than wild type). In a studied group, BChE activity range was similar to those observed in other populations. BChE activity screening allowed to detect UA and UF phenotypes in 26 (2.2%) and 15 (1.2%) individuals, respectively. Observed UA or UF phenotypes were confirmed by direct sequencing and heterozygous c.293A > G or c.1253G > T substitutions were identified in all cases. Nine out of 18 (50%) individuals with BChE activity below 2000 U/L had a mutation in 5'UTR (32G/A), intron 2 (c.1518-121T/C) or exon 4 (c.1699G/A; the K variant mutation). Majority of the individuals with BChE activity ≥6000 U/L were wild type. To summarize, the range of BChE activity in a Polish population is similar to those observed in other countries. We conclude that the BChE phenotyping assay is a reliable method for identification of individuals with the UA and UF genotypes.

Effect of the glycosphingolipid, GM1 on localization of dibucaine in phospholipid vesicles: a fluorescence study

Interaction of the local anesthetic dibucaine with small unilamellar vesicles of dimyristoylphosphatidylcholine (DMPC) and dioleoylphosphatidylcholine (DOPC) containing different mole percents of monosialoganglioside (GM1) has been studied by fluorescence spectroscopy. Fluorescence measurements on dibucaine in the presence of phospholipid vesicles containing various amounts of GM1 yielded a pattern of variation of wavelength at emission maximum and steady-state anisotropy which indicated that the microenvironment of dibucaine is more hydrophobic and rigid in membranes that contain GM1 than in membranes without it. Experiments on quenching of fluorescence from membrane-associated dibucaine by potassium iodide showed reduced quenching efficiency with the increase in GM1 content of the vesicles, demonstrating lesser accessibility of the iodide quenchers to dibucaine in the presence of GM1, when compared to that in its absence. Total emission intensity decay profiles of dibucaine yielded two lifetime components of approximately 1 and approximately 2.8-3.1 ns with mean relative contributions of approximately 25 and approximately 75%, respectively. The mean lifetime in vesicles was 20-30% lower than in the aqueous medium and showed a definite increase in presence of GM1 from that in the absence of it. All the spectral properties point that dibucaine encountered regions of membrane containing significant amount of GM1 and penetrated deeper in hydrophobic core of the bilayer.

Blood concentrations of tetracaine and its metabolite following spinal anesthesia

Blood concentrations of tetracaine and its metabolite, p-butylaminobenzoic acid, were measured after spinal anesthesia with tetracaine which had been administered to patients under going orthopedic surgery. Tetracaine, an ester anesthetic, was given to 10 patients, the dose was 8-14mg, and blood samples were collected 1, 2 and 6h after the injection of tetracaine. We used gas chromatography/mass spectrometry for purposes of analysis. Tetracaine was not detected in any blood sample, but the metabolite was detected in each sample with the mean concentrations of 126.5, 97.9 and 43.3ng/ml at 1, 2 and 6h, respectively. This data will be useful in determination of the cause of death after spinal anesthesia with tetracaine.

Trifluoperazine and dibucaine-induced inhibition of glutamate-induced mitochondrial depolarization in rat cultured forebrain neurones

1. Glutamate receptor activation has been previously shown to result in mitochondrial depolarization and activation of the mitochondrial permeability transition pore in cultured neurones. In this study, we characterized the effects of two putative permeability transition inhibitors, namely trifluoperazine and dibucaine, on mitochondrial depolarization in rat intact, cultured forebrain neurones. 2. Permeability transition was monitored by following mitochondrial depolarization in neurones loaded with the mitochondrial membrane potential-sensitive fluorescent indicator, JC-1. Trifluoperazine (10 20 microM) and dibucaine (50-100 microM) inhibited or delayed the onset of glutamate-induced permeability transition. 3. We also investigated the effects of trifluoperazine and dibucaine on neuronal recovery from glutamate-induced Ca2+ loads. Trifluoperazine affected Ca2+ recovery in a manner similar to the mitochondrial Na+/Ca2+ exchange inhibitor, CGP-37157, while dibucaine had no apparent effect on Ca2+ recovery. Therefore, inhibition of permeability transition does not appear to be involved in Ca2+ recovery from glutamate-induced Ca2+ loads. 4. Trifluoperazine and dibucaine did not inhibit [3H]-dizocilpine binding at the concentrations that prevented mitochondrial depolarization. 5. These studies suggest that trifluoperazine and dibucaine inhibit permeability transition in intact neurones. Trifluoperazine also appears to inhibit mitochondrial Na+/Ca2+ exchange. These drugs should prove to be valuable tools in the further study of the role of mitochondrial permeability transition in glutamate-induced neuronal death.

Interaction of dibucaine with the transmembrane domain of the Ca(2+)-ATPase of sarcoplasmic reticulum

The site of interaction of dibucaine with the Ca(2+)-ATPase of rabbit sarcoplasmic reticulum, an ion-transporting membrane protein, was investigated by determining the effect of dibucaine on the denaturation of the transmembrane domain and the aqueous domain containing, respectively, the high-affinity Ca2+ binding sites and the site of ATP hydrolysis. In the absence of Ca2+, a single irreversible denaturation transition with Tm approximately equal to 49 degrees C is observed for the Ca(2+)-ATPase by differential scanning calorimetry (DSC). In the presence of Ca2+, but not Mg2+, Sr2+, or Ba2+, a new high-temperature transition is observed that has been shown to be due to stabilization of the transmembrane region [Lepock, J. R., Rodahl, A. M., Zhang, C., Heynen, M. L., Waters, B., & Cheng, K. H. (1990) Biochemistry 29, 681-689]. The maximum stabilization corresponds to a shift in Tm of 13.8 degrees C, and Hill analysis indicates that the Ca2+ binding site yielding stabilization has a Kd = 2.5 x 10(-4) M with a cooperativity (n) of 1. Thus, stabilization is due to Ca2+ binding not to the high-affinity sites but to one of the previously observed sites of low or intermediate affinity, which must be located in the transmembrane or stalk subdomains. Dibucaine has little effect on the Tm of the aqueous domain, but it decreases the Tm of the transmembrane domain with Kd approximately equal to 4.1 x 10(-4) M and a cooperativity of approximately 1.6, implying that destabilization is due to the binding of dibucaine to sites of intermediate or moderately high affinity.(ABSTRACT TRUNCATED AT 250 WORDS)

Fluorescence studies of a local anesthetic-phospholipid interaction

Steady-state and time-resolved fluorescence data are reported for the local anesthetic dibucaine in the absence and presence of phospholipid vesicles. These vesicles were comprised of dimyristylphosphatidyl choline and approximately 10% dimyristylphosphatidyl glycerol. Solute quenching studies show the bound drug to be protected from collision with iodide ion. The fluorescence lifetime of dibucaine is not significantly changed upon binding to vesicles. The fluorescence anisotropy of dibucaine increases upon association with the vesicles. Anisotropy decay measurements show that the rotational correlation time, phi, of bound dibucaine is increased about one hundred fold over that for free dibucaine. This indicates that the rotational motion of bound dibucaine is slowed by its interaction with the phospholipids. However, we find no evidence that the rotational motion of bound dibucaine is anisotropic.

Local anesthetic-phospholipid interactions. Effects of ionic strength, temperature, and phospholipid mixtures on the binding of dibucaine to phospholipids

The nature of the interaction of amphipathic drugs, such as dibucaine, with phospholipid bilayer membranes was investigated using equilibrium dialysis. Profiles for the binding of cationic dibucaine to unilamellar vesicles were obtained at different temperature and ionic strengths, and for mixtures of neutral phospholipid dimyristylphosphatidylcholine (DMPC) with negatively charged dimyristylphosphatidylglycerol (DMPG). The degree of binding of the cationic drug at pH 5 was found to be higher at temperatures above the Tm of DMPC (24 degrees C) than below Tm. Also enhanced drug binding was found to occur as the concentration of monovalent salt was increased (0.01-0.85 M) and as the percentage of DMPG was increased. Using the Stern and Guoy-Chapman model, which takes into consideration electrostatic effects, we were able to simultaneously fit all our binding data with a minimum of fitting parameters. These parameters (for data at 45 degrees C) are an association constant, K, of 330 M-1, a maximum possible number of drug molecules absorbed per unit surface of vesicle, sigma m+, of 1.70 x 10(-2) A2, and a surface area per bound drug, gamma D, of 48 A2. The data were fitted equally well by an alternate model in which binding of the drug is described as a partitioning equilibrium, with factors included for electrostatic effects and surface expansion caused by drug intercalation between the fatty acid chains.

The use of monolayers for simple and quantitative analysis of lipid-drug interactions exemplified with dibucaine and substance P

The interaction between lipids and water soluble amphiphiles was investigated by means of a monolayer technique, monitoring the area increase at constant surface pressure. The area increase could be quantitated and binding isotherms at different surface pressures were measured. A comparison of dibucaine binding to monolayers and bilayers showed that a surface pressure of 32 mN/m best represents the packing density in a lipid bilayer (Seelig, 1987). Binding isotherms measured for charged dibucaine and substance P (SP) were analyzed by means of two different models. If electrostatic effects were ignored the binding of dibucaine and SP showed biphasic Scatchard plots. If, however, electrostatic effects were taken into account by means of the Gouy-Chapman theory, the insertion of both amphiphiles was best described in terms of a partitioning into the monolayer lipids. The hydrophobic binding constant was Kp = 660 +/- 80 M-1 for charged dibucaine inserting into coarse liposomes or monolayers at 32 mN/m (Seelig et al., 1986) and 1-1.8 M-1 for SP inserting into monolayers at 32 mN/m (Seelig and Macdonald, 1989).

Tumor cell permeability to peplomycin

The uptake of [3H]peplomycin-Cu(II) ([3H]PEP-Cu(II)) into various tumor cell lines was studied. The time course of [3H]PEP-Cu(II) uptake into AH66, AH66F, Ehrlich and P388 cells was biphasic. The first phase of uptake was completed within 5 minutes. The second, slower phase, of uptake into AH66, AH66F and Ehrlich cells increased linearly with incubation time, but that into P388 cells reached a plateau level. In L1210 cells, only the first rapid uptake was observed. The lower uptake into P388 and L1210 cells during the second phase may be related to their insensitivity to PEP. However, the uptake into AH66F cells was higher than that into AH66 cells, although AH66F cells were less sensitive to PEP than AH66 cells. Deamide PEP was detected in intact cells which had taken up [3H]PEP-Cu(II) during 4 hours. This confirmed that PEP-Cu(II) was transported into the cell, the copper removed and PEP metabolized to deamide PEP. [3H]PEP-Cu(II) uptake into AH66 and AH66F cells increased in proportion to the extracellular concentration of drug up to at least 200 micrograms/ml, suggesting that uptake was not mediated by a carrier system. Metabolic inhibitors such as NaN3 and 2,4-dinitrophenol enhanced [3H]PEP-Cu(II) uptake, but did not influence efflux. Uptake was also enhanced by membrane modifiers such as dibucaine and chlorpromazine which increase the fluidity of lipid membranes. The results suggest that PEP-Cu(II) was taken up into tumor cells by passive diffusion, controlled by an energy-dependent cell membrane barrier.

Partitioning of local anesthetics into membranes: surface charge effects monitored by the phospholipid head-group

The binding of the charged form of two local anesthetics, dibucaine and etidocaine, to bilayers composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) was measured simultaneously with ultraviolet spectroscopy and deuterium magnetic resonance. Because of their amphiphilic molecular structure, both drugs intercalate between the lipid molecules, increasing the surface area and imparting a positive electric charge onto the membrane. The ultraviolet (UV) binding isotherms were therefore analyzed in terms of a model which specifically took into account the bilayer expansion as well as the charge-induced concentration variations near the membrane surface. By formulating a quantitative expression for the change in surface area upon drug intercalation and combining it with the Gouy-Chapman theory, the binding of charged dibucaine and etidocaine to the lipid membrane was best described by a partition equilibrium, with surface partition coefficients of 660 +/- 80 M-1 and 11 +/- 2 M-1 for dibucaine and etidocaine, respectively (pH 5.5, 0.1 M NaCl/50 mM buffer). Deuterium magnetic resonance demonstrated further that the binding of drug changed the head-group conformation of the lipid molecules. Invoking the intercalation model, a linear variation of the deuterium quadrupole splittings of the choline segments with the surface charge density was observed, suggesting that the phosphocholine head-group may act as a 'molecular electrometer' with respect to surface charges.

Combined boric acid and cinchocaine chloride poisoning in a 12-month-old infant: evaluation of haemodialysis

A mixture containing 3 g of boric acid and 300 mg of cinchocaine chloride prescribed due to painful dental protrusion was accidentally ingested by a 12-month-old girl. She developed violent vomiting and coughing. Irritability, tremor, seizures and a delirious reaction. She was treated with diazepam, intubated, sedated and ventilated. Her diuresis was stimulated with furosemide and fluid. Within the first 24 h she was treated with haemodialysis twice on femoral catheters. Her renal function was unaffected. In two days she fully recovered. The maximum measured levels of boric acid and cinchocaine chloride approximately 6 h after ingestion were 26 micrograms/ml and 71 ng/ml respectively. The plasma half-life of boric acid was 7.0 h and decreased to 3.6 and 4.4 h during the two haemodialyses. The total body clearance of boric acid increased correspondingly from 21 ml/min to 41 and 34 ml/min. The in vitro clearance of boric acid of the dialyser was later determined to be 18 ml/min. It is concluded that haemodialysis is valuable in the treatment of boric acid intoxication because it increases the elimination of the drug even in patients without any sign of renal toxicity.

Locations and dynamical perturbations for lipids of cationic forms of procaine, tetracaine, and dibucaine in small unilamellar phosphatidylcholine vesicles as studied by nuclear Overhauser effects in 1H nuclear magnetic resonance spectroscopy

Locations and dynamical perturbations for lipids of local anesthetics (procaine . HCl, tetracaine . HCl, and dibucaine . HCl) in sonicated egg yolk phosphatidylcholine (PC) vesicles have been studied by 1H-1H nuclear Overhauser effect (NOE) measurements. It was found that tetracaine and dibucaine bind much strongly to the neutral lipids than does procaine and that their mobilities are lowered to such an extent that spin diffusion is transmitted (i.e., omega 2 tau c2 much greater than 1). The intermolecular NOEs between drugs and PC were more effective in the case of dibucaine than with tetracaine, indicating that dibucaine binds to the lipids more strongly than tetracaine; this order agrees well with that of anesthetic potency. However, it was only tetracaine that gave any appreciable dynamical perturbation to the PC vesicles when they were monitored by the extent of transfer of the negative NOE from alpha-methylene protons to choline methyls, olefinic methines, acyl methylenes and terminal methyl protons. This finding was interpreted as being due to the differences in the locations of these drugs in small unilamellar vesicles: (1) procaine interacts with lipids very weakly at the outer surface of the vesicles; (2) tetracaine binds to the lipids both at the outer and inner halves of the bilayer, inserting its rod-like molecule in a forest of acyl chains of PC; (3) dibucaine binds tightly to the polar head-group of PC, which resides only at the outer half of the bilayer vesicles. It was concluded that the relative order of anesthetic potency within these drugs can be correlated not with the ability to affect membrane fluidity but with the ability to bind to lipids at the polar head-group of the bilayer vesicles.

Local anesthetic-phospholipid interactions. The pH dependence of the binding of dibucaine to dimyristoylphosphatidylcholine vesicles

The interaction of the local anesthetic dibucaine with unilamellar vesicles of dimyristoylphosphatidylcholine was studied by equilibrium dialysis. Saturating binding profiles (as a function of dibucaine) were found, with apparent association constant ranging from 1.26 X 10(3)M-1 to 2.57 X 10(3)M-1 as pH is increased from 5.0 to 7.5. The number of phospholipid molecules comprising a binding site was found to be about 5 at each pH. Analysis of the data was also achieved using the Stern model, which takes into account the electrostatic effect on binding of the cationic drug due to the build up of a surface potential.

Uptake of dibucaine into large unilamellar vesicles in response to a membrane potential

Local amine anesthetics appear to exert their effects in the charged (protonated) form on the cytoplasmic side of excitable membranes. Two features of interest are the mechanism whereby these drugs move across the membrane to the inner monolayer and the actual membrane concentrations achieved. In this work, we have investigated the influence of a K+ diffusion potential, delta psi, on the transmembrane distribution and concentration of the local anesthetic dibucaine employing large unilamellar vesicle systems. It is demonstrated that egg phosphatidylcholine large unilamellar vesicles exhibiting a delta psi (interior negative) actively accumulate dibucaine to achieve high interior concentrations. 31P and 13C nuclear magnetic resonance studies show that the internalized drug is localized to the vesicle inner monolayer, and suggest that the protonated form of the anesthetic is the species that is actively transported. The inner monolayer anesthetic concentrations thus achieved can be an order of magnitude or more larger than predicted on the basis of anesthetic lipid-water partition coefficients. It is suggested that these effects may be related to the mechanisms whereby local anesthetics are localized and concentrated at their sites of action in nerve membranes.

Adsorption of local anesthetics on phospholipid membranes

In order to elucidate various types of adsorption modes of local anesthetics in membranes, a study of local anesthetic adsorption on lipid membranes was made by measuring electrophoretic mobility of phospholipid vesicles in the presence of local anesthetics of various concentrations in the vesicle suspension solution. The amounts of local anesthetics to be adsorbed on the membrane surface were deduced from the electrophoretic mobility of a phosphatidylcholine vesicle at various concentrations of the cationic form of local anesthetics. The order of surface adsorption of local anesthetic was dibucaine greater than tetracaine greater than procaine. A surface partition coefficient, Ks = 1/ACs, was introduced, where A is the membrane surface area per local anesthetic molecule adsorbed and Cs the surface concentration of local anesthetics. The amounts of local anesthetic adsorbed on phosphatidylserine membrane were much greater than that of the phosphatidylcholine membrane. It was deduced that the major factor for this large adsorption was due to the enhancement of cationic forms of local anesthetic concentrations at the charged membrane surface. Divalent cations inhibited such surface adsorption of local anesthetics by reducing surface concentrations of local anesthetics where the surface potential of the negatively charged membrane surface was influenced by the presence of divalent cations in the solution as well as by the reduction of fixed surface charges due to divalent cation binding. Some association modes of local anesthetics on nerve membranes are discussed with the results obtained in the above adsorption study.

Metabolism of dibucaine: isolation and identification of urinary basic metabolites in the rat, rabbit and man

The metabolism of dibucaine was studied in the rat, rabbit and man. A total of ten basic metabolites other than dibucaine were detected in the urine samples of three species by thin-layer chromatography (TLC) and gas chromatography (GC), and structures of these metabolites were identified by comparison of the properties given by TLC, GC and gas chromatography-mass spectrometry (GC-MS) with those of authentic compounds. Four of these metabolites were new metabolites which were found in the rabbit or human urine; two were identified as the 2', 3'-dihydroxybutoxy product (M-6, diol) and its N-deethyl product (M-2), and others were identified as the 2'-hydroxyethoxy product (M-8, alcohol) and its N-deethyl product (M-3). One of the two hydroxyl groups on M-5 was at 6-position on the quinoline ring, while another was assumed to be at 3'-position on the O-alkyl side chain. There were apparent species differences with regard to the major metabolites found in each species; i.e. M-10 and M-5 in rat, M-6 and M-4 in rabbit, and M-8 and M-4 in man. Small amounts of the conjugated basic metabolites were observed in the urine of all three species. The new metabolic pathways to the diols (M-2 and M-6) or the alcohols (M-3 and M-8) were also discussed.

[Relations between the physico-chemical properties, the chemical reactivity and the local anesthetic activity. 32. (Part 1): Binding capacity of a structural protein (wool) to local anesthetics]

1. The general part deals with the molecular structure of nerve membranes and different local-anesthetic substances as well as the various possibilities of local-anesthetic binding to the nerve membrane. Albumin is usually chosen as a model protein in such investigations, a short extract of which is given. 2. The special part includes the chemical composition and properties of wool macroprotein, the model system used in the present paper. We determined its protein-binding values with cinchocain and tetracain homologues and various known commercial products of local anesthetics (oxybuprocain, parethoxyprocain and tetracain). The binding constants of these substances on wool protein are shown. 3. A statistically confirmed relationship between the alkyl chain length and the strength of protein binding is given. The free energy per CH2-group ranges between 400 and 500 cal/mol and its larger in cases of low pH values. 4. From the present data, a relationship between the binding constant and the partition constant of each substance of the homologous series studied could easily be observed, which further makes it possible to estimate the characteristic protein-binding constant Kp and also the change in pi-values with the change in free reaction energy of the substances. 5. The large differences in the binding values of the different binding mechanisms, which most probably are dependent on the variable binding affinities of the functional groups as well as on steric factors. But as in the homologous series, only substituents like alkyl amino and alkoxy could be changed, the possibility of some other binding process depending on the alkyl chain length of these groups could not be ruled out. Since the alky groups are non-polar, hydrophobic binding plays a role.