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PubMed1976

Ion-pair chromatography of acidic drug metabolites and endogenic compounds.

Liquid-liquid chromatographic systems based on ion-pair partition with silica microparticles as the support for the stationary phase have been used for the separation of anionic compounds of biochemical and pharmacological interest. A high separating efficiency can be obtained with both aqueous and organic mobile phases and the retention is easily regulated by the nature and the concentration of the quaternary ammonium counter ion, present in the aqueous phase. The influence of the composition of the liquid phases on the selectivity and separating efficiency has been studied, as well as equilibration methods and the stability of the systems. Examples are given of separations of sulphonamides, barbiturates, glucuronic and sulphuric acid conjugates of steroidal compounds and phenols glycine conjugates of carboxylic acids (hippuric, nicotinuric and salicyluric acid) and anionic metabolites of biogenic amines (indoleacetic, benzoic, mandelic and phenylacetic acid derivatives).

Barbiturates↗
PubMed2003

Transport of Cl- across the plasma membrane during pollen grain germination in tobacco.

The role of Cl- transport across the plasma membrane was studied in an early step of pollen grain germination in tobacco Nicotiana tabacum L. The Cl- channel blockers, 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) and niflumic acid, completely suppress the germination with IC(50) approximately 8 micro M. At this concentration NPPB reduces the rate of Cl- efflux out of pollen grain by 1.8-fold in the interval 5-12 min, and niflumic acid reduces the rate 1.2-fold. 4,4;-Diisothiocyanatostilbene-2,2;-disulfonic acid, a known inhibitor of Cl- channels and antiporters, completely suppresses germination as well (IC(50) = 240 micro M), but has no effect on the rate of Cl- efflux. Inhibitors of chloride co-transporters, such as furosemide, bumetanide, and bis(1,3-dibutylbarbituric acid)pentamethine oxonol, suppress the germination by less than 50%. This set of data suggests that NPPB-sensitive anion channels are involved in the activation of pollen grains in the early stage of germination.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed2000

Effect of barbiturates on hydroxyl radicals, lipid peroxidation, and hypoxic cell death in human NT2-N neurons.

BACKGROUND: Barbiturates have been shown to be neuroprotective in several animal models, but the underlying mechanisms are unknown. In this study, the authors investigated the effect of barbiturates on free radical scavenging and attempted to correlate this with their neuroprotective effects in a model of hypoxic cell death in human NT2-N neurons. METHODS: Hydroxyl radicals were generated by ascorbic acid and iron and were measured by conversion of salicylate to 2,3-dihydroxybenzoic acid. The effect of barbiturates on lipid peroxidation measured as malondialdehyde and 4-hydroxynon-2-enal was also investigated. Hypoxia studies were then performed on human NT2-N neurons. The cells were exposed to 10 h of hypoxia or combined oxygen and glucose deprivation for 3 or 5 h in the presence of thiopental (50-600 microM), methohexital (50-400 microM), phenobarbital (10-400 microM), or pentobarbital (10-400 microM), and cell death was evaluated after 24 h by lactate dehydrogenase release. RESULTS: Pentobarbital, phenobarbital, methohexital, and thiopental dose-dependently inhibited formation of 2,3-dihydroxybenzoic acid and iron-stimulated lipid peroxidation. There were significant but moderate differences in antioxidant action between the barbiturates. While phenobarbital (10-400 microM) and pentobarbital (10-50 microM) increased lactate dehydrogenase release after combined oxygen and glucose deprivation, thiopental and methohexital protected the neurons at all tested concentrations. At a higher concentration (400 microM), pentobarbital also significantly protected the neurons. At both 50 and 400 microM, thiopental and methohexital protected the NT2-N neurons significantly better than phenobarbital and pentobarbital. CONCLUSIONS: Barbiturates differ markedly in their neuroprotective effects against combined oxygen and glucose deprivation in human NT2-N neurons. The variation in neuroprotective effects could only partly be explained by differences in antioxidant action.

Barbiturates↗
PubMed1983

Comparison of local anesthetics as bronchodilator aerosols.

Lidocaine aerosols have been ineffective at preventing airway constriction provoked by non-reflex stimuli. To determine if there were any advantages to using more potent amide-type local anesthetics or local anesthetics from other chemical classes, the authors compared the protection afforded by pretreatment with aerosols of lidocaine, bupivacaine, hexylcaine, and procaine against a subsequent prolonged challenge (5 min) with 10% citric acid aerosols in barbiturate-anesthetized Basenji-Greyhound dogs. The local anesthetics were administered as aerosols (4% solutions) for 10 min immediately preceding the citric acid challenge. In control experiments, that employed pretreatment with aerosols of isotonic saline rather than local anesthetics, the citric acid challenge aerosol increased pulmonary resistance by an average of 3.3 +/- 0.8 (+/- SE) cmH2O X 1(-1) X s during the first 15-min postchallenge, and reduced dynamic compliance by one-third during this time. None of the local anesthetics prevented citric-acid-induced changes in pulmonary mechanics. The average increases in pulmonary resistance (0-15 min postchallenge) elicited by citric acid aerosols in dogs pretreated with lidocaine, hexylcaine, bupivacaine, and procaine were 2.1 +/- 0.6, 2.1 +/- 0.6, 3.2 +/- 1.3, and 3.3 +/- 1.0 cmH2O X 1(-1) X s, respectively. The authors concluded that local anesthetic aerosols have little or no effect against other than reflex bronchoconstriction, and none of those tested were more effective than lidocaine.

Anesthetics, Local↗
PubMed1989

Increased response of cerebellar cGMP to kainate but not NMDA or quisqualate following barbital withdrawal from dependent rats.

Female Sprague-Dawley rats were maintained on a diet of powdered food containing barbital for 8 weeks before the drug was abruptly withdrawn. Twenty-four hours later both barbital-dependent and control rats were injected intracerebroventricular (i.c.v.) with saline or one of four doses of kainic acid (KA) or in a separate experiment with saline or one of three doses of N-methyl-D-aspartic acid (NMDA) or of quisqualic acid (QA). After 4.5 min, the animals were killed by focused microwave irradiation, and the cerebella were collected. The levels of cyclic guanosine 3',5' monophosphate (cGMP) were markedly elevated in the cerebella of barbital-withdrawn rats when compared to controls. When compared to saline treatment, KA, at all dosages, resulted in a significantly greater elevation of cerebellar cGMP in the barbital-withdrawn rats than was induced by drug withdrawal alone. Only the two higher dosages of KA produced a significant elevation of this parameter in the control rats. Unlike KA, neither QA or NMDA produced any greater elevations of cGMP in barbital withdrawn rats than were induced by drug withdrawal alone. These collective results suggest that there is an increase in the response to KA but not QA or NMDA following the withdrawal of barbital from dependent rats.

Animals↗
PubMed1988

Benzodiazepines and barbiturate potentiate the pre- and postsynaptic gamma-aminobutyric acid (GABA)A receptor-mediated response in the enteric nervous system of guinea pig small intestine.

To determine whether or not presynaptic gamma-aminobutyric acid (GABA) receptors regulate the release of GABA, we examined properties of the presynaptic GABA receptor and compared the findings within the case of the postsynaptic GABA receptor, using the longitudinal muscle with myenteric plexus (L-M) preparation of guinea pig small intestine. Muscimol, but not baclofen, reduced the Ca++-dependent release of [3H]GABA evoked by high K+ in the presence of tetrodotoxin from L-M preparation of the small intestine preloaded with [3H]GABA. Bicuculline, picrotoxin and furosemide antagonized the effect of muscimol. Diazepam, clonazepam and pentobarbital potentiated the muscimol-induced inhibition of high K+-evoked release of [3H]GABA. The potentiating effect of clonazepam was antagonized by Ro 15-1788. Muscimol induced a Ca++-dependent and tetrodotoxin-sensitive release of [3H]acetylcholine from L-M preparation preloaded with [3H]choline. The effect of muscimol was antagonized by bicuculline, picrotoxin and furosemide. Diazepam, clonazepam and pentobarbital potentiated the muscimol-evoked release of [3H]ACh. The potentiation of muscimol effect by clonazepam was inhibited by Ro 15-1788. These results indicate that both the GABA autoreceptor and postsynaptic receptor may possess the same property which is related to benzodiazepine and barbiturate binding sites in the enteric nervous system of the guinea pig small intestine. The benzodiazepine binding site seems to be of central type.

Acetylcholine↗
PubMed1989

Requirement for a 1-kilobase 5'-flanking sequence for barbiturate-inducible expression of the cytochrome P-450BM-3 gene in Bacillus megaterium.

In a previous publication (Wen, L.-P., and Fulco, A. J. (1987) J. Biol. Chem. 262, 6676-6682), we described the cloning of the gene encoding cytochrome P-450BM-3, a catalytically self-sufficient fatty acid monooxygenase induced by barbiturates in Bacillus megaterium. We have now subcloned a 1.6-kilobase segment of DNA from this cloned gene that includes the barbiturate-responsive regulatory region as well as 88 bases encoding the NH2-terminal portion of cytochrome P-450BM-3. From this, we generated two series of 5' and 3' deletion derivatives and examined their effects on gene expression. When the 1.6-kilobase fragment or the 1.3-kilobase 5'----3' deletion derivative is inserted into Escherichia coli on a vector containing a promoterless chloramphenicol acetyltransferase (CAT) gene with the sequence encoding the NH2-terminal portion of P-450BM-3 placed immediately in front of the CAT gene, CAT activity is constitutive and unaffected by pentobarbital. On the other hand, the basal level of CAT is low in B. megaterium transformed by the same construct but is strongly inducible by pentobarbital. Furthermore, the multicopy plasmid containing this regulatory region causes a dramatic decrease in both the basal and pentobarbital-induced expression of chromosomally encoded P-450BM-3 in B. megaterium. This competition effect, unlike CAT expression, is independent of the orientation of the regulatory DNA segment in the plasmid. Removal of 0.3 kilobase or more from the 3' end of the 1.6-kilobase segment of DNA or 0.6 kilobase from the 5' end abolishes the competition effect and also eliminates basal and inducible CAT expression in B. megaterium. In transformed E. coli, constitutive CAT expression is maintained when as little as 0.3 kilobase of DNA from the 3' end of the 1.6-kilobase segment is inserted in the correct orientation in front of the CAT gene. The data are consistent with the hypothesis that the synthesis of cytochrome P-450BM-3 in B. megaterium is under positive control and requires gene interaction with at least one trans-acting factor, presumably a protein, to activate transcription from the P-450BM-3 promoter. The binding of this putative protein is mediated by at least two regulatory regions (R1 and R2) that span about 1 kilobase of the 5'-flanking region of the gene.

Bacillus megaterium↗