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PubMedDate not supplied

Metabolism of R-(+)-and S-(minus)-pentobarbital by hepatic microsomes from male rats.

Hepatic microsomes from male rats hydroxylate R-(+)- and (-)-[2-14-C]pentobarbital to the diasterioisomeric 3'-alcohols: metabolite I (1'RS, 3'SR)- and metabolite II (1'RS, 3'RS)-5-ethyl-5-(3'-hydroxy-1'methylbutyl) barbituric acids. The rate is linear up to 1.5 mg of microsomal protein per ml of incubation mixture and for up to 16 min. The metabolism of R-(+)-pentobarbital led to production of nearly equal quantities of metabolites I and II with a total hydroxylation of 1.08 nmol/min/mg of protein. On the other hand, the S-(-) pentobarbital gave 3- to 5-fold less of metabolite I than II and a total hydroxylation of 1.42 nmol/min/mg of protein. The KM values for formation of metabolite I were 381 muM from R-(+)- and 241 muM from the S-(-)-pentobarbital, while for metabolite II they were 115 muM from R-(+)- and 68 muM from S-(-)-pentobarbital. These data suggest that there are at least two enzymes catalyzing the hydroxylation of pentobarbital, one to give metabolite II and another or others to give metabolite I.

Animals↗

PubMed1990

[Determination of thiocyanate in serum with ion-selective liquid membrane electrodes].

The manufacture of a liquid membrane type thiocyanate ion selective electrode on the basis of crystalviolet thiocyanate or methylene blue thiocyanate solved in nitrobenzene is described. This electrodes are available for the determination of the thiocyanate ion in agents with high levels on chlorid or protein, for instance in serum. Thiocyanate levels in serum from smokers and nonsmokers determinated by this electrodes differ significant from values that were obtained by the barbituric acid method, but they were in good agreement with values determinated by ion exchange chromatography. It can be assumed that its possible to ascertain the part of the dissociated thiocyanate by means of the ion selective electrodes and the ion exchange chromatography.

Chemical Phenomena↗

PubMed1977

Fluorimetric determination of the active form of tetracycline, chloretetracycline and oxytetracycline in partially decomposed solutions.

The content of tetracycline (1), chlortetracycline (2) and oxytetracycline (3) has been determined by use of the fluorimetric method in partially decomposed acqueous solutions of different pH values. The procedure consisted in the extraction of fluorescent calcium and 5.5-diethyl-barbituric acid complexes of 1 and 3 (with 2 calcium complex only) into an organic solvent. In the method, only complexes with undecomposed 1--3 show a strong fluorescence. Products of decomposition of the antibiotics did not affect significantly analytical results. Comparative investigations have been carried out with 1--3 using t.l.c. and turbidimetry.

Chlortetracycline↗

PubMed1989

[Measurement of the biochemical marker of smoking: urinary nicotine metabolites].

A novel, barbituric acid method of detecting urinary nicotine metabolites was evaluated for use as an objective test of smoking. Urine samples were collected from 289 male smokers and 167 male nonsmokers. The smokers recorded the number of cigarettes smoked on the previous day. This method correctly classified the subjects as smokers or nonsmokers. There was a significant positive correlation (r = 0.587, P less than 0.001) between the urinary nicotine metabolites/creatinine ratios and number of cigarettes smoked. This method can be performed very rapidly and reagent costs are very cheap. It is a good objective test of smoking and nicotine intake.

Biomarkers↗

PubMed1986

Products distribution in the oxidation of thymine with hydroxyl radicals.

In the oxidation of thymine with hydroxyl radical generated from L-ascorbic acid/copper(II) ion/O system, four reaction products, thymine glycol(TG), N-formyl-N'-pyruvylurea(FPU), 5-hydroxymethyluracil(HMU) and 5-hydroxy-5-methyl barbituric acid(HMBA) were obtained. A reaction scheme was proposed to explain the products distribution observed.

Chemical Phenomena↗

PubMed1987

Effect of methohexital on the relationship between hexokinase distribution and energy metabolism in neuroblastoma cells.

Cultured neuroblastoma cells (clone neuro-2a) were used to demonstrate the influence of an anesthetic on energy metabolism by acting on the intracellular distribution of hexokinase activity. First of all, there was to be shown that a relationship between the intracellular hexokinase distribution and energy metabolism actually exists in neuroblastoma cells. Since glucose-6-phosphate could be assumed to be the main regulator of this enzyme distribution, experimental conditions were chosen where the glucose-6-phosphate level was changed significantly. A decrease in the glucose-6-phosphate level in the cells was achieved by deprivation of glucose and oxygen for 30 min. Under these conditions the glucose-6-phosphate level and the soluble hexokinase activity decreased significantly. The effect was reversible when glucose and oxygen were again added to the incubation medium of the cells. On the other hand, the antimetabolite 6-aminonicotinamide produced an accumulation of glucose-6-phosphate which caused an increase in the soluble hexokinase activity. These results brought evidence for a correlation of intracellular hexokinase distribution and energy metabolism. When alpha-(+/-)-5-allyl-1-methyl-5-(1-methyl-2-pentinyl) barbituric acid (methohexital) was added to the incubation medium of the neuroblastoma cells, a dose-dependent increase in soluble hexokinase activity was measurable, whereas the glucose-6-phosphate level was decreased at least within a therapeutically relevant dosage range of the anesthetic. This effect was reversible when methohexital was washed out from the cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Cells, Cultured↗

PubMedDate not supplied

[Factors regulating mono-oxygenase induction by phenobarbital xenobiotics].

The main nongenetic factors are revealed which regulate the catalytic activity and substrate specificity of microsomal monooxygenases preinduced by phenobarbital-type xenobiotics (barbituric acid and pyrazolone derivatives). It is shown that a blockage of the primary microsomal metabolism of an inducer is the obligate condition for its inductive effect on the content and activity of cytochrome P-450. On this basis it is practicable to convert the typical monooxygenase substrates into inducers of the enzyme biosynthesis by the blockage of the molecule site subjected to monooxygenation. A model is suggested which shows the phenobarbital participation in the formation of the specific configuration of the active site of cytochrome P-450 synthesized; the latter catalyzes the oxidation of a number of substrates by the way typical of inducer itself.

Aminopyrine↗

PubMed1984

Non-steroidal anti-inflammatory agents and hepatic lipid peroxidation in normal- and carrageenin-treated rats.

A single oral dose of indomethacin (3 mg/kg b.w.) and phenylbutazone (200 mg/kg b.w.) induces an enhancement of thio-barbituric acid reacting substances (TBArs) formation by total liver homogenate of male rats. On the contrary, treatment with ibuprofen (200 mg/kg b.w., os) does not influence the susceptibility of hepatic tissue to "in vitro" lipid peroxidation. The former two chemicals do not interfere with the pro-oxidant action of carbon tetrachloride (1.0 ml/kg b.w., os) whereas ibuprofen limits the extension of TBArs production provoked by the haloalkane. Further, ibuprofen does not affect the level of glutathione in liver tissue, while indomethacin and phenylbutazone do. Similar results fatty acids was studied "in vivo" by monitoring conjugated diene absorption spectrum of hepatic microsomal lipids. Oedema produced acutely by injection of carrageenin into the plantar region of rat hind paw does not influence the peroxidative decomposition of hepatic lipids as found "in vitro" and/or "in vivo" neither in the presence nor in the absence of all the mentioned chemicals. Carbon tetrachloride administered orally (1.0 ml/kg b.w.) appears to be able to depress significantly the paw oedema induced by carrageenin but does not potentiate the anti-inflammatory effect of the tested non-steroid agents.

Animals↗

PubMedDate not supplied

[Effect of benzobamil on the morpho-functional state of liver and drug metabolism in experimental CC14 intoxication].

An anticonvulsive drug benzobamil (3-benzoyl-5-ethyl-5-isoamyl barbituric acid) improved the antitoxic function of liver tissue, increased the content of RNA, protein, cytochrome P-450, accelerated the oxidation of NADH, NADPH as well as metabolism of xenobiotics in microsomes of rats with CCl4 intoxication. Benzobamil normalized the hepatocyte structure, corrected the fatty dystrophy, stimulated the protein synthesis, increased the content of glycogen as well as activity of succinate and lactate dehydrogenases and stabilized the lysosomal membranes.

Animals↗

PubMed1982

Improved isocratic liquid-chromatographic simultaneous measurement of phenytoin, phenobarbital, primidone, carbamazepine, ethosuximide, and N-desmethylmethsuximide in serum.

We describe an improved "high-pressure" liquid-chromatographic assay for simultaneous determination in serum of the five major antiepileptic drugs (ethosuximide, primidone, phenobarbital, phenytoin, and carbamazepine) and N-desmethylmethsuximide (the compound that must be quantitated for therapeutic drug monitoring of the antiepileptic drug methsuximide). Serum protein is precipitated with an acetone solution containing 5-ethyl-5-(p-methylphenyl)barbituric acid as the internal standard. The centrifuged supernate is injected onto the chromatographic column. Drugs and internal standard are eluted at 30 degrees C with mobile phase containing acetonitrile/methanol/phosphate buffer (17/28/55 by vol) at a flow rate of 0.7 mL/min, monitored at 195 nm. Analysis time is about 20 min. Quantitation is by measurement of peak areas. Analytical and absolute recoveries varied from 95 to 104%. Within-day coefficients of variation ranged from 1.6 to 5.4%, between-day CVs from 0.0 to 3.4% in subtherapeutic, therapeutic, and toxic samples. Resolution of therapeutic concentrations of all six drugs was complete. As yet, we have found no drug or drug metabolite that interferes.

Carbamazepine↗

PubMedDate not supplied

Simultaneous rapid HPLC determination of anticonvulsant drugs in plasma and correlation with EMIT.

A method is presented for measuring simultaneously five anti-convulsants (primidone, ethosuximide, phenobarbital, carbamazepine and diphenylhydantoin) in serum and plasma by high-performance liquid chromatography (HPLC) using alphenal (5 - allyl - 5 - phenyl - barbituric acid) as the internal standard. All five drugs are separated from each other and, in the case of primidone, from its metabolie, 2 - phenyl - 2 - ethyl - malondiamide. Total HPLC time for the separation is seven minutes. The chromatography is performed on a C-8 reverse phase column with a mobile phase consisting of acetonitrile/phosphate buffer (35/65) at 25 degrees C. The eluted drugs are detected at 220 nm and quantitated from their peak heights relative to that of the internal standard. The lower limits of detection for each drug is 200 ng per ml for primidone, 1000 ng per ml for ethosuximide, 200 ng per ml for phenobarbital, 100 ng per ml for carbamazepine and 200 ng per ml for diphenylhydantoin. Analytical recoveries for the five drugs ranged from 97 to 107 percent. Correlation of results for 187 specimens by enzyme-immunoassay (emit) was 0.981 for primidone, 0.827 for ethosuximide, 0.975 for phenobarbital, 0.889 for carbamazepine and 0.990 for diphenylhydantoin. In the HPLC assay, ethotoin was found to interfere with phenobarbital and phensuximide with carbamazepine.

Anticonvulsants↗

PubMed1982

[Mechanisms of the protective effect of methohexital on cerebral energy metabolism].

The purpose of the present investigation was to study the effect of alpha-(+/-)-5-allyl-1-methyl-5-(1-methyl-2-pentinyl) barbituric acid (methohexital, Brevimytal sodium) on brain energy metabolism. The model of the isolated perfused rat brain was used. The high-energy phosphates, some substrates of glycolysis and the intracellular distribution of hexokinase activity were measured in the cortical tissue of the isolated rat brain after 30 min of perfusion, after ischemia or anoxia and after various recovery periods. The EEG was recorded as a parameter of the neuronal activity. The following results were obtained: 1. Ischemia and anoxia accelerated the glycolysis rate which was inhibited by methohexital. 2. The energy metabolism was more rapidly normalized after ischemia or anoxia when methohexital was added to the perfusion medium (0.2 mmol/l). 3. Compared to the corresponding preparation, the spontaneous electrical activity of the isolated brain was maintained in ischemia or anoxia for a longer period and appeared again more rapidly in the recovery periods when methohexital was present. 4. Phosphofructokinase activity was inhibited by methohexital in the recovery period after ischemia or anoxia, respectively. 5. Inhibition of hexokinase activity predominated in the surgical stage of anesthesia when glycolysis rate was not accelerated. Methohexital seemed to inhibit hexokinase activity by solubilizing the mitochondrial bound form.

Adenosine Triphosphate↗

PubMed1981

[Glycosylation of hemoglobin and the minor hemoglobins : techniques and diagnostic study (author's transl)].

Hemoglobin Alc is the result of non-enzymatic binding of a glucose molecule at the NH2 terminal of the beta chain. Assay of glycosylated hemoglobin is of great utility for the control efficacity of antidiabetic treatments, since such levels provide the clinician with an excellent index of glucose metabolism over the weeks preceding the assay. Methods proposed for this assay include isoelectric focalization, colorimetric assays during thio-barbituric acid and especially, cation exchange chromatography. When automated, this last technique allows selective assay of Hb Alc and appears to provide the most accurate results. Certain causes of error must nevertheless be considered, in particular more rapid turnover of the erythrocytic population and the presence of Hb F which, in all chromatographic techniques, is eluted along with Hb Alc.

Chromatography, Ion Exchange↗

PubMed1981

[The blocking potencies and the mode of blockade by pentobarbital and phenobarbital, examined on various types of ACh-receptor activities (author's transl)].

The ganglion cells of Aplysia contain three types of ACh-receptors. The activation of one type produces Na+-dependent depolarization (DNa-type). The other receptors are HK- and HCl-types ; activation produces K+- and Cl--dependent hyperpolarization, respectively. Effects of pentobarbital-sodium (PB), phenobarbital-sodium (PhB), and barbituric acid (BA) on each type of receptor activity were compared with each other. ACh-induced responses were evaluated by the change in membrane conductance. PBV showed different blocking potencies for each type of receptor activity, their ratio being DNa : HCl : HK=1 : 0.5 : 0.02. PhB showed a similar potency ratio, but the potency for each type was approximately a half of PB. BA blocked neither type of receptor activities. The mode of blockade was studied by plotting dose-inhibition curve for each type of receptor activity, and found to be "noncompetitive" in all types. It was suggested that PB and PhB had much greater blocking potency for the receptor activities of "nicotinic type" than that for the "muscarinic type". It was concluded that PB does not compete with ACh for the common binding site at the receptor, but it binds to a certain allosteric site which controls the opening of ionic channels, particularly for Na+ and Cl-.

Animals↗

PubMedDate not supplied

Opening of frog skin sodium channels by phenobarbital.

This paper presents a study of the action of phenobarbital (anticonvulsant barbituric acid with pK1 = 7.3 and pK2 = 11.8) on the short-circuit current and on the transepithelial conductance of the frog isolated skin. An increase in these parameters was found after addition of the drug to the outside medium (apical). This effect is significantly higher at pHs lower than pK1, suggesting that the neutral form of this substance is the active form. All studies were performed at pH 7. Phenobarbital induces a depolarization of the apical barrier and an increase in 22Na+ radioactive tracer fluxes, which parallel the increase in the observed short-circuit current. This suggests an opening of the Na+ channels in this barrier. A dose-response curve shows that phenobarbital possibly acts on two different sites, with different affinity constants and stoichiometries. To further characterize these channels, comparative studies with oxytocin (a hormone that opens amiloride-sensitive Na+ channels in the apical side) were performed. The results show that phenobarbital causes the same percentage of increase in Isc in control and oxytocin-pretreated skins. Amiloride was also found to inhibit the phenobarbital-sensitive channels with an affinity constant [KAMIL = (60 +/- 1.78) x 10(-8) M] insensitive to the phenobarbital concentration.

Amiloride↗

PubMedDate not supplied

[Study of oxidative enzymes of the lignin-degrading fungus Pleurotus ostreatus].

The elctrophoretic separation in polyacrylamide gel of laccase and peroxidase isoenzymes of the lignin-degrading fungus Pleurotus ostreatus was investigated. The optimal electrophoretic conditions were found: in the electrode buffer tris-diethyl barbituric acid pH 7.0 in the gradient gel-4-10% acrylamide. Seven peroxidase isoenzymes oxidizing base benzidine and guaiacol were identified and five laccase isoenzymes reacting with specific substrates-p-phenylene diamine, alphs-naphthol, pyrogallol, hydroquinone were determined.

Agaricales↗

PubMedDate not supplied

[Polarized fluoroimmunoanalysis of phenobarbital using the TD(x) analyzer from "Abbott" laboratories].

Polarographic fluoroimmunoassay was developed for identification and estimation of phenobarbital in urine. The study was carried out using TDx-analyzer "Abbott" (USA) under conditions of automatic service by modified program N 21 intended for analysis of kanamycin. In the procedure developed rabbit antiserum against phenobarbital was used at the initial dilution 1:2 and the tracer 5-ethyl-5-(4'-fluoroscein thiocarbamyl aminophenyl)barbituric acid was applied at the initial concentration of 60 nmol/l. The minimal content of phenobarbital evaluated in urine was as small as 0.09 microgram/ml and it was measured in the limits of 0.5 microgram/ml. Specificity of the analysis and its reproducibility were studied. The results of the polarographic fluoroimmunoassay correlated highly to the data of EMIT-st-assay and HPLC.

Animals↗

PubMedDate not supplied

[The characteristics of the functional activity of cellular immunity factors in relation to the use of general anesthetics from different pharmacological groups in operations for optic nerve neurolysis].

The functional activity of cellular immunity was studied in 26 patients with opticochiasmatic arachnoiditis as a model of autoimmune involvement of the brain after administration of common anesthetics of different pharmacological groups. Injection of ketamine as the induction and basic component of general combined anesthesia leads to reduction of neurosensitization induced by the pathologic process; it is paralleled by the optimal activation of the suppressor component of lymphocytes and a reduction of sensitization to brain antigen. In contrast to ketamine, barbiturates augment neurosensitization and lead to depression of the lymphocyte activity, this confirming the anti-immunopathological effect of barbituric acid derivatives. Ketamine is advisable for patients with various immunopathological states.

Anesthesia, General↗