Ethacizin metabolism in humans

1. The major metabolites of ethacizin (ethyl 10-[3-diethylaminopropionyl]phenothiazine-2-carbamate) have been isolated from human urine by h.p.l.c. and identified by determination of u.v., i.r., n.m.r. and mass spectra and comparison with spectra of synthetic standard compounds. 2. The pathways of metabolism of ethacizin include N-de-ethylation, sulphoxidation, N-10 amide hydrolysis, aromatic hydroxylation and conjugation.

Vanadium K-edge X-ray-absorption spectroscopy of the functioning and thionine-oxidized forms of the VFe-protein of the vanadium nitrogenase from Azotobacter chroococcum

Vanadium K-edge X-ray-absorption spectra were collected for samples of thionine-oxidized, super-reduced (during enzyme turnover) and dithionite-reduced VFe-protein of the vanadium nitrogenase of Azotobacter chroococcum (Acl*). Both the e.x.a.f.s and the x.a.n.e.s. (X-ray-absorption near-edge structure) are consistent with the vanadium being present as part of a VFeS cluster; the environment of the vanadium is not changed significantly in different oxidation states of the protein. The vanadium atom is bound to three oxygen (or nitrogen), three sulphur and three iron atoms at 0.215(3), 0.231(3) and 0.275(3) nm respectively.

Mössbauer studies of solid thionin-oxidized MoFe protein of nitrogenase

Recently Hagen et al. (Hagen, W. R., Wassink, H., Eady, R. R., Smith, B. E., and Haaker, H. (1987) Eur. J. Biochem. 169, 457-465) reported the observation of S = 7/2 EPR signals for thionin-oxidized nitrogenase MoFe protein. Here we have studied the protein from Azotobacter vinelandii and Klebsiella pneumoniae with Mössbauer and EPR spectroscopies, with the following results: when the MoFe protein is oxidized by addition of stoichiometric amounts (6-8 equivalents) of dissolved thionin, the well characterized P-cluster state Pox results. Pox has an as yet undetermined, but half-integer electronic spin; however, the state is EPR-silent. In contrast, oxidation by addition of a large excess of solid thionin powder, the method used by Hagen et al., yields mixtures with variable proportions of two oxidized P-cluster forms, namely the familiar Pox and the new state Pox(S = 7/2) observed by Hagen et al. The Mössbauer data suggest that Pox and Pox(S = 7/2) are isoelectronic. The two states, however, have distinct electronic structures; the Mössbauer spectra of Pox exhibit the characteristic trapped-valence Fe2+ site, whereas the spectra of Pox(S = 7/2) lack this feature. Hagen et al. have proposed two new P-cluster models. We conclude that one of the models is incompatible with the Mössbauer data and that the basic assumptions of the other model are not supported by the available data. Finally, the Mössbauer data show that either oxidation method puts the cofactor centers into the diamagnetic state Mox.

Heterogeneity of [3H]neurotensin bindings: studies with dynorphin, L-156,903 and levocabastine

The binding of [3H]neurotensin (NT) to membranes from rat forebrain was complex, exhibiting 'high' affinity (Kd approximately 0.5 nM) and 'low' affinity (Kd approximately 5.0 nM) binding components. Dynorphin A(1-13) (DYN A(1-13] and L-156,903 (N-oxo-3-(10H-phenothiazine-10-yl)propyl-1- arginyl-1-prolyl-1-phenylalanine) potently inhibited [3H]NT binding to brain with shallow biphasic competition curves. Saturation binding studies conducted in the presence or absence of DYN A(1-13) or L-156,903 indicated that these compounds, like levocabastine, exhibited substantial selectivity for 'low' affinity NT site. Structure-activity studies indicated rigid structural requirements for the NT binding activity of DYN A(1-13) and L-156,903. In contrast to the results using brain tissue, DYN A(1-13), L-156,903 and levocabastine were very weak or inactive to inhibit [3H]NT binding to rat uterus. These studies further characterize the heterogeneity of [3H]NT binding in vitro and demonstrate clear tissue differences in binding within a given species.

Human metabolism of phenothiazines to sulfoxides determined by a new high performance liquid chromatography--electrochemical detection method

The metabolism of phenothiazine drugs may contribute to both their therapeutic and toxic actions by production of active metabolites in vivo. Idiosyncratic reactions or treatment failure may be a consequence of differing patterns of metabolism in different patients. In this report, a modification of our method for the detection of metabolites of phenothiazines is described, which also permits the simultaneous determination of sulfoxide metabolites in human plasma. Application of this method to human plasma identifies marked individual differences in patterns of phenothiazine metabolism.

RNA content and thionin binding capacity of brain--a quantitative approach to determine cellular degradation

60 rats were divided into one control and 2 test groups of 20 male animals in each. Brains from control animals were taken out immediately after killing, and in the test groups (I and II) after brain cell damage by controlled autolysis at 37 degrees C for 6 and 18 h, respectively. Ten animal brains from each group were used for estimation of RNA content. The remaining 10 brains each of the test and control groups were homogenised in 0.001% thionin in formaline saline and incubated for thionin binding. The supernatants were read spectrophotometrically and the amount of thionin in the sediment(s) was calculated. The amount of sediment bound thionin in mg per 100 g brain was expressed as "thionin binding capacity" (TBC) of the brain. RNA content of the brain in control and test groups (I and II) was found to be 248.33 +/- 6.83 (100%), 210.83 +/- 8.61 (84.9%), and 190.83 +/- 10.21 (76.85%) mg per 100 g of the brain. Thionin binding capacity was 6.30 +/- 0.12 (100%), 4.82 +/- 0.17 (76.45%), and 3.49 +/- 0.39 (55.45%) mg per 100 g brain, in the 3 groups respectively. Both parameters showed similar decreasing tendencies with increasing brain damage i.e. in the groups I and II. The decrements of the 2 parameters were highly significant (P less than .001), hence, they could be utilised to assess the brain damage.

Structural determinants of sigma receptor affinity

The structural determinants of sigma receptor affinity have been evaluated by examining a wide range of compounds related to opioids, neuroleptics, and phenylpiperidine dopaminergic structures for affinity at sigma receptor-binding sites labeled with (+)-[3H]3-PPP. Among opioid compounds, requirements for sigma receptor affinity differ strikingly from the determinants of affinity for conventional opiate receptors. Sigma sites display reverse stereoselectivity to classical opiate receptors. Multi-ringed opiate-related compounds such as morphine and naloxone have negligible affinity for sigma sites, with the highest sigma receptor affinity apparent for benzomorphans which lack the C ring of opioids. Highest affinity among opioids and other compounds occurs with more lipophilic N-substituents. This feature is particularly striking among the 3-PPP derivatives as well as the opioids. The butyrophenone haloperidol is the most potent drug at sigma receptors we have detected. Among the series of butyrophenones, receptor affinity is primarily associated with the 4-phenylpiperidine moiety. Conformational calculations for various compounds indicate a fairly wide range of tolerance for distances between the aromatic ring and the amine nitrogen, which may account for the potency at sigma receptors of structures of considerable diversity. Among the wide range of structures that bind to sigma receptor-binding sites, the common pharmacophore associated with high receptor affinity is a phenylpiperidine with a lipophilic N-substituent.

Methyltrypsin: a novel probe of proteinase-inhibitor interactions

Incubation of trypsin with m-guanidinobenzenesulfonic acid methyl ester (mGBSOM) under mild conditions resulted in its quantitative and specific conversion to N-3-methylhistidinyl-57-trypsin (methyltrypsin). The interactions of alpha-2-plasmin inhibitor (alpha 2PI) and alpha-1-proteinase inhibitor (alpha 1PI) with the active-site modified enzymes methyltrypsin and dehydroalanyl-195-trypsin (anhydrotrypsin) were studied by thionine difference spectroscopy. For methyltrypsin the KA with alpha 1PI and alpha 2PI was 2.7 X 10(5) M-1 and 1.3 X 10(5) M-1, respectively, and with anhydrotrypsin, 7.0 X 10(3) M-1 and 3.2 X 10(5) M-1, respectively.

Efficacy, safety, hemodynamic effects, and pharmacokinetics of high-dose moricizine during short- and long-term therapy

Moricizine, 15 mg/kg, was given to 10 patients with frequent ventricular ectopic depolarizations, eight of whom had previously been treated unsuccessfully with antiarrhythmic drugs. A single-blind inpatient study was followed by therapy for up to 6 months. Two patients developed aggravation of arrhythmia during inpatient therapy. Of the eight patients who completed the inpatient study, seven achieved greater than or equal to 80% suppression of total ventricular ectopic depolarizations (P less than 0.001). During inpatient therapy the mean of the individual patients' suppression of total ventricular ectopic depolarizations was 87.9%, paired ventricular beats 99.3%, nonsustained ventricular tachycardia 99.6%, and premature atrial contractions 89.0%. Suppression was maintained during long-term therapy. The PR interval increased 27% (P less than 0.001), QRS interval increased 10% (P less than 0.0001), QTc increased 1% (P not significant), and JTc decreased 2% (P not significant). Heart rate, blood pressure, and left ventricular performance at rest and exercise were unchanged by moricizine. Moricizine half-life was 9.2 +/- 3.4 hours. Plasma levels of moricizine decreased after 10 days of therapy, suggesting induction of metabolic enzyme systems.

Phenothiazine binding by a homolog of calpactin, the pp60src tyrosine kinase substrate

Microvilli isolated from 13762 mammary ascites tumor cells contain a major calcium-sensitive protein (AMV-p35) that can be isolated with microvillar microfilament cores prepared by Triton X-100 extraction in the presence but not absence of calcium. AMV-p35 can be readily purified from ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid extracts of the microfilament cores by chromatography on an anion exchange column, to which it does not bind. Immunoblot analysis indicates that AMV-p35 is related to calpactin I, the pp60src tyrosine kinase substrate. In the presence of calcium, AMV-p35 binds approximately 4 mol of chlorpromazine per mole of protein in a binding process showing apparent positive cooperativity, similar to calmodulin; however, in contrast to calmodulin, AMV-p35 also binds phenothiazine in the absence of calcium.

Studies on the ligand specificity and potential identity of microsomal antiestrogen-binding sites

Synthetic nonsteroidal antiestrogens are bound intracellularly by two high affinity saturable bindings sites, the estrogen receptor and the microsomal antiestrogen-binding site (AEBS). In order to further define the structural requirements for ligand binding to AEBS from rat liver and the MCF 7 human breast cancer cell line, the relative binding affinities of an extensive series of structurally related ligands were investigated using competitive binding assay techniques. The groups of compounds studied were: analogues of the triphenylethylene antiestrogens, Cl 628 and tamoxifen; analogues of cyclofenil; bibenzyl and stilbene derivatives; analogues of the cytochrome P-450 inhibitor SKF-525A; phenothiazine derivatives; and a series of structurally related compounds with a variety of pharmacological activities. High affinity binding to AEBS required the presence of both a hydrophilic basic aminoether side chain and a hydrophobic aromatic ring structure (di- or tricyclic for maximal affinity). Structural modifications to either influenced binding affinity. Aromatic substitution either raised (CF3) or lowered (OH, OCH3) affinity, apparently by electronic effects transmitted through the benzene nucleus. Side chain structure was the major determinant of binding affinity, but its influence was complex and dependent upon terminal amino group structure, side chain branching and substitution, and tissue source of AEBS. Optimal binding affinity was shown by side chains bearing basic heterocyclic amino terminal groups. Other cellular sites that are known to bind antiestrogens with relatively high affinity include calmodulin, cytochrome P-450, and histamine, dopamine, and muscarinic receptors. Binding studies using a variety of pharmacologically active and radiolabeled ligands selective for these sites, including those for dopamine D1 and D2 receptors ([3H]fluphenazine, [3H]flupenthixol, [3H]spiperone, and [3H]SCH 23390) and histamine H1 receptors ([3H]pyrilamine), demonstrated that several of these compounds interact with AEBS with high affinity. However, the ligand specificity and other binding properties of the AEBS as determined by competitive binding studies and Scatchard analysis show this site to be a molecular entity truly distinct from these other cellular binding sites.

Calmodulin is labeled at lysine 148 by a chemically reactive phenothiazine

10-(3-Propionyloxysuccinimide)-2-(trifluoromethyl)phenothiazine (POS-TP) is a chemically reactive calmodulin antagonist: 2 mol are incorporated per mol of calmodulin when excess reagent is used, and only lysyl side chains are modified. Tryptic peptide mapping demonstrated that a single unique site on calmodulin reacts at low molar ratios of POS-TP. Labeled peptides were isolated and analyzed by amino acid composition and sequence analysis. The unique site was identified as Lys148 of calmodulin, the carboxyl-terminal residue. At higher molar ratios of the reagent Lys21, Lys75, and Lys77 are labeled as are several minor peptides that were not characterized.

[Romanowsky dyes and the Romanowsky-Giemsa effect. 4. Binding of azure B to DNA]

We investigated the binding of azure B to DNA (calf thymus) over a wide range of concentrations of the dye (CF) and the nucleic acid (CN) using absorption spectroscopy [CF and CN represent the total concentrations of the ye (F) and the mononucleotide units (N) of the DNA, respectively]. The binding isotherms of the dye to DNA in aqueous solutions were determined. In addition, we analysed the composition of insoluble DNA/azure B precipitates that are formed in presence of an excess of azure B. These precipitates are of particular interest, because Giemsa staining is usually performed using high dye concentrations. Azure B easily forms dimers in aqueous solutions. When determining the binding isotherms, the equilibrium between free monomers and dimers must be taken into account. Therefore, we determined the dimerisation constant (Kd) of azure B from the concentration dependency of its absorption spectra in water at the standard temperature T = 298 K (25 degrees C), Kd = 6.5 X 10(3) M-1 (experimental conditions: tris buffer, pH 7.2; concentration of Na ions, CNa = 0.002 M). As the CNa value increases, the dimerisation constant rises rapidly. When the azure B concentration is very low and there is an excess of DNA, ordinary Scatchard and Langmuir isotherms are observed. Monomer dye cations are bound to DNA, these cations being in equilibrium with free monomers in the solution. In order to obtain the Scatchard binding constant (Ks) and the binding parameter (n) spectroscopically, it is necessary to determine the extinction coefficient (epsilon Fb) of the monomer bound (b) dye molecules (F) at one analytical wave number (upsilon a). The three constants can be determined simultaneously using an iterative technique that combines Scatchard isotherms and the Benesi-Hildebrand extrapolation, CN----infinity. We obtained Ks = 1.8 X 10(5) M-1 and n = 0.18 (25 degrees C; tris buffer, pH 7.2; CNa = 0.002 M). At very low dye (CF) and competitor (CNa) concentrations, only 18% of the anionic binding sites of the DNA are capable of binding the dye cations. With increasing CNa values the concentration of bound azure B cations decreases rapidly. The Na cations displace the bound dye cations and act as a competitor. The Ks value also greatly depends on the competitor concentration (CNa).(ABSTRACT TRUNCATED AT 400 WORDS)

Glutathione oxidation during peroxidase catalysed drug metabolism

The peroxidase catalyzed oxidation of certain drugs in the presence of glutathione (GSH) resulted in extensive oxidation to oxidized glutathione (GSSG). Extensive oxygen uptake ensued and thiyl radicals could be trapped. Only catalytic amounts of drugs were required indicating a redox cycling mechanism. Active drugs included phenothiazines, aminopyrine, p-phenetidine, acetaminophen and 4-N,N-(CH3)2-aminophenol. Other drugs, including dopamine and alpha-methyl dopa, did not catalyse oxygen uptake, nor were GSSG or thiyl radicals formed. Instead, GSH was depleted by GSH conjugate formation. Drugs of the former group, e.g. acetaminophen, aminopyrine or N,N-(CH3)2-aniline have also been found by other investigators to form GSSG and hydrogen peroxide when added to hepatocytes or when perfused through an isolated liver. Although cytochrome P-450 normally catalyses a two-electron oxidation of drugs, serious consideration should be given for some one-electron oxidation resulting in radical formation, oxygen activation and GSSG formation.

Monoclonal antibodies against a 60 kDa phenothiazine-binding protein from Trypanosoma brucei can discriminate between different trypanosome species

The dominant structure of the cytoskeleton of the Trypanosomatidae consists of a tight array of singlet pellicular microtubules, which surround the entire cell body. These microtubules are in close and stable contact with the cellular membrane. These contacts can be selectively disrupted by the action of phenothiazine drugs, which are potent trypanocides in vitro. Phenothiazine-affinity chromatography of detergent solubilized proteins from Trypanosoma brucei has resulted in the isolation of a protein of an apparent molecular weight of 60 000. Polyclonal antibodies raised against this protein (p60) have been used to investigate the presence of similar proteins in other protozoa. No such crossreacting proteins have been observed outside the family Trypanosomatidae. Within this family, a strong crossreactivity was observed with Crithidia fasciculata, while only a marginal reaction was seen with two species of Leishmania and, quite unexpectedly, also with the stercorarian trypanosomes T. cruzi and T. rangeli. Different monoclonal antibodies against p60 are able to clearly distinguish different subgenera of salivarian trypanosomes, and most notably to differentiate between various isolates of T. congolense. Therefore, these antibodies may prove valuable for diagnostic and epidemiological applications.

LG 30435 is a new bronchodilator agent with multiple sites of action

LG 30435, a new quaternary derivative of the H1-histamine antagonist mequitazine, was evaluated against bronchospasm induced by different agonists. This compound inhibited equipotently methacholine- and histamine-induced contractions of isolated guinea-pig trachea. When administered to guinea-pig by the i.v. and/or the aerosol route, LG 30435 inhibited dose dependently the bronchospasm induced by acetylcholine and histamine and to a lesser degree that induced by 5-hydroxytryptamine and LTD4. When compared to that of mequitazine, its potency was higher in each case, up to 500-fold when tested in vitro against methacholine. LG 30435 also counteracted antigen-induced bronchospasm both in passively sensitized guinea-pigs and in actively sensitized rats. This compound had a rapid onset of action and an adequate duration after aerosol administration. It was poorly absorbed both by the oral and the aerosol routes and it did not appear to penetrate the blood-brain barrier. These results show that LG 30435 is a new aerosol bronchodilator agent, which, due to its multiple pharmacodynamic actions and to its suitable pharmacokinetics, is potentially useful in the therapy of obstructive airways disease.

Biomolecular photoalterations mediated by phenothiazine derivatives

This survey focuses on recent developments in the field of the ultraviolet photochemistry and photobiology of phenothiazine derivatives. One of the major alterations introduced by this kind of photosensitized reaction is a covalent addition of the photosensitizer or one of its photoproducts onto the macromolecular target. This reaction has been observed with soluble and membrane proteins, lipids and DNA. In the latter case, the addition occurs at the level of guanine residues and leads to inhibition of DNA replication.

Structural analysis of the calcium-binding protein calmodulin from Ascaris suum obliquely striated muscle

Calmodulin was purified from the obliquely striated skeletal muscle of Ascaris suum. The calmodulin had a molecular weight of 16,400 and the amino acid composition indicated it is highly similar to other purified calmodulins, showing insignificant variation in 12 of 17 residues. In the residues that showed variation, a trend towards conservative substitution was observed. Spectrophotometric absorption maxima of 276 nm and 283 nm were observed. A molar absorption coefficient of 7,800 was calculated. Calcium-dependent binding to phenothiazine Affi-Gel confirmed that calcium binding induces conformation changes characteristic of calmodulin. Double reciprocal analysis of phosphodiesterase activation by A. suum calmodulin gave a Kapp of 40 nM.

A theoretical study of the binding of phenothiazine derivatives to residues 82-93 of calmodulin

A theoretical study was performed of the interaction of four phenothiazine derivatives, promethazine, promazine, trifluopromazine, and trifluoperazine, with a fragment (82-93) of calmodulin, held in the alpha-helical conformation. The computations were performed in the framework of the SIBFA 2 procedure (sum of interactions between fragments computed ab initio), which uses analytical formulas based on ab initio self-consistent field computations. The interaction energy is the sum of the intermolecular phenothiazine-oligopeptide interaction energy and of the separate intramolecular energy variations of the phenothiazine and of the side chains of the oligopeptide upon complex formation. The ordering of interaction energies of the four investigated phenothiazines parallels the ordering of their experimentally measured affinities for calmodulin, with a maximum affinity for trifluoperazine. The principal features of the trifluoperazine complex are a short hydrogen bond between the piperazinium proton and one anionic oxygen of Glu 87, and hydrophobic interactions between the piperazinium ring and Val 91 and between the methylene chain and Ala 88, together with partial insertion of the phenothiazine ring and the--CF3 substituent between Phe 89 and Phe 92.

Phenothiazine and butyrophenone intoxication in children

Antipsychotic agents are widely used for the treatment of psychotic disorders as well as for the acute treatment of nausea and vomiting, cough and cold treatments, and as supplementary agents for sedation for minor surgical or diagnostic procedures. There are many different circumstances in which the clinician may encounter a child who has experienced antipsychotic drug toxicity, such as from an acute accidental ingestion or as a side effect from therapeutic use. The phenothiazines and butyrophenone drugs have many pharmacologic actions. Thus, a wide range of clinical symptoms and signs may be encountered with their use. Treatment of antipsychotic drug toxicity includes general supportive care and monitoring, along with specific treatment of certain situations such as acute extrapyramidal syndromes and neuroleptic malignant syndrome. An awareness of the diverse and complex manifestations that may be associated with these agents will greatly aid in the evaluation of a child who presents with unusual behavioral or neurologic problems. Due to the unpredictable toxicity of these drugs, routine therapeutic use for such conditions as nausea and vomiting and as cough or cold aids is not recommended.

[Correlation between the anti-arrhythmia effect of ethacizin and pharmacokinetic parameters in a model of rhythm adoption by the heart]

Pharmacokinetics and pharmacodynamics of ethacizin were studied in a model of rhythm adoption by the heart, with the drug administered intravenously to anesthetized cats. A relation was demonstrated between blood ethacizin pattern and the drug's biphasic effect on the adoption of stimulation-imposed pace by the heart and ventricular fibrillation threshold. The estimated correlation coefficients, reflecting the relationship between the development of ethacizin anti-arrhythmic and antifibrillation effects and variation of its plasma levels between 10 and 120 min after the administration, were rather high (-0.85 and +0.93, respectively). Ethacizin shows anti-arrhythmic and antifibrillation activity when its plasma levels are between 2400 and 200 ng/ml.

Interaction between calmodulin and five different spin-labelled chlorophenothiazines

The binding to purified calmodulin of five spin-labelled derivatives of chlorophenothiazine was investigated by e.s.r. spectrometry and by the antagonizing potency on the calmodulin-dependent activation of myosin light chain kinase. The results of a comparative study and the influence of pH and ionic strength on the binding support the occurrence of an electrostatic binding involving the terminal amino group of the side-chain of the chlorophenothiazine. These results are discussed in relation to the specificity of the interaction that holds the antipsychotic drug-calmodulin complex together.

[Use of ion-exchange sorbents for determining drug preparations and their metabolites in biological fluids by high-performance liquid chromatography]

High performance liquid chromatography has acquired great importance recently for an analysis of the drugs in biological fluids of the body. Phase inversion sorbents are particularly widely used today. However, the use of ion-exchange sorbents is fairly promising for an analysis of the drugs capable of ionizing in an aqueous solution. The authors illustrate the use of the latter ones for determination in the blood, urine and saliva of man of a number of the cardiologic drugs (etmozine, nonachlazine, verapamil, prazosin, propranolol, nadolol). Ion-exchange sorbents make it possible to attain better results than inverse phase ones, since they retain the drugs selectively and do not retain the endogenous substances of lipid nature. As regards verapamil, prazosin and propranolol, the unchanged drug and polar metabolites could be determined jointly, with such a determination being not feasible with the use of phase inversion sorbents. Separation of the diastereoisomers of nadolol was achieved in the blood and urine of patients who received the drug.