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PubMed1990

[Potential cardiotonic agents. 10. Synthesis and positive inotropic action of 5-(4-pyridinyl)- and 5-phenyl-substituted 2-alkylthio-3-cyan-pyridines and their S-oxidation products].

The alkylation of the 5-(4-pyridinyl)- and 5-phenyl-substituted 3-cyan-2(1H)-pyridinethiones 1 with alkyl iodides and halomethylcarbonyl compounds led to the 2-alkylthio-pyridines 3a-c, 3e, 3f and the thieno[2,3-b]pyridines 4, respectively. In an other way the 2-ethylthio-5-(4-pyridinyl)pyridines 3b and 3d were formed from the corresponding 2-chloroderivatives and ethylmercaptan. By means of oxidation of the 2-alkylthio-pyridines 3 with 3-chloroperbenzoic acid and potassium permanganate, respectively, the 2-sulfinyl- and 2-sulfonyl-pyridines 5 and 6 were obtained. The 3-cyano-5-(4-pyridinyl)pyridine-2-sulfonic acid 7 was prepared by oxidation of the 2(1H)-pyridinethione 1a with potassium permanganate. Some derivatives possess positive inotropic properties.

Animals↗

PubMed1980

Inhibition of thromboxane synthesis and platelet aggregation by pyridine and its derivatives.

Pyridine inhibited the conversion of PG endoperoxide to TXA2 catalyzed by TX synthetase from human platelet and swine lung microsomes. The inhibitory potency of pyridine is abolished by derivatizing pyridine at the 2-position but is increased by introducing hydrophobic substituents at 3- or 4-positions, with 3-substituted pyridines being the most potent inhibitors. Inhibition by pyridine and its derivatives was also selective, since other enzymes in the arachidonic acid cascade were not significantly affected. Pyridine and the active derivatives also inhibited human platelet aggregation induced by arachidonic acid or ADP.

Animals↗

PubMed1995

3-Methylcholanthrene and pyridine effects on CYP1A1 and CYP1A2 expression in rat renal tissue.

The effects of 3-methylcholanthrene (3-MC) and pyridine on rat renal cytochrome P450 (CYP) 1A1 and 1A2 mRNA expression have been examined by Northern-blot analysis and reverse transcriptase-polymerase chain reaction (RT-PCR), followed by Southern-blot analysis of the PCR products. Northern-blot hybridization and RT-PCR analyses of kidney poly(A)+ RNA revealed that 3-MC treatment produced a time-dependent increase in the renal CYP1A1 and 1A2 mRNA levels, with CYP1A1 and 1A2 mRNA levels maximally increased at 24 and 18 hr, respectively, after treatment. These data were confirmed via RT-PCR analysis using a subsaturating level of cDNA template and by Southern-blot analysis of the PCR products. This approach served as the foundation for examining the effects of pyridine on CYP1A1 and 1A2 expression in renal tissue. RT-PCR analysis of renal CYP1A1 and 1A2 poly(A)+ RNA levels after treatment with pyridine (200 mg/kg/day for 3 consecutive days) revealed that CYP1A1 mRNA levels were maximally elevated approximately 10-fold after pyridine treatment for 2 consecutive days, whereas CYP1A2 mRNA levels were maximally elevated approximately 3-fold at 24 hr after treatment. The mRNA levels of glyceraldehyde 3-phosphate dehydrogenase, which served as an internal control, remained constant after 3-MC or pyridine treatment. These results show that expression of CYP1A1 and 1A2 mRNAs is enhanced in renal tissue after exposure to 3-MC or pyridine, and that constitutive expression of CYP1A1 seems to be greater than that of CYP1A2 in renal tissue.

Animals↗

PubMed1991

Phenotypic variation in the outer membrane protein composition of Actinobacillus (Haemophilus) pleuropneumoniae: non-specific effect of exogenous pyridine nucleotide supply.

Actinobacillus pleuropneumoniae, grown in batch culture, was provided with pyridine nucleotides at concentrations that limited the final growth yield (pyridine nucleotide-deficient cultures) or did not determine the final extent of growth (pyridine nucleotide-sufficient cultures). Sarkosyl-extracted outer membranes from stationary phase, pyridine nucleotide-sufficient organisms contained 23,000 Mr and 43,000 Mr polypeptides that were absent (23,000 Mr) or barely detectable (43,000 Mr) in outer membranes from stationary phase, pyridine nucleotide-deficient organisms or exponential phase organisms. When growth ceased due to exhaustion of pyridine nucleotide, the ratio of the major outer membrane polypeptides (31,000, 38,000 and 69,000 Mr) was altered, becoming more like the ratio found with exponential phase organisms. Similar results were obtained when growth ceased due to glucose exhaustion at low biomass concentrations demonstrating that diverse nutrient deprivations can induce similar changes in outer membrane protein profile. All of these polypeptides were recognized by porcine immune sera indicating their production by A. pleuropneumoniae growing in vivo.

Actinobacillus pleuropneumoniae↗

PubMed2000

Estimation of the total range of 1J(CC) couplings in heterocyclic compounds: pyridines and their N-oxides, the experimental and DFT studies.

A very large set of one-bond spin-spin carbon carbon coupling constants, 1J(CC), has been measured for 32 variously mono- and disubstituted pyridine N-oxides and for 14 substituted pyridines. The N-oxides studied were 2-, 3- and 4-monosubstituted isomers, and a series of disubstituted compounds. A variety of substituents has been employed (CH3, COCH3, C5H4NO, CN, F, Br, Cl, OH, OCH3, NH2, N(CH3)2 and NO2), which allowed us to study substituent effects thoroughly. Good linear relationships between 1J(C3C4) in 3- and/or 4-substituted pyridine N-oxides and 1J(CipsoCortho) in benzenes and between 1J(C2C3) in 2- and/or 3-substituted pyridine N-oxides and 1J(CipsoCortho) in benzenes have been found. An analogous linear relationship has been observed between 1J(C3C4) in 3- and/or 4-substituted pyridines and 1J(CipsoCortho) in benzenes. It has been also concluded that, by analogy to 1J(CC) couplings in substituted benzenes, those in pyridines and their N-oxides are the substituent electronegativity dependent. The estimated total range covered by 1J(CC), couplings in substituted compounds varies, in the case of 1J(C2C3) couplings for example, from 25 Hz in 2-lithiopyridine N-oxide to ca. 100 Hz in 2,3-difluoropyridine N-oxide and from 18 Hz in 2-lithiopyridine to 92 Hz in 2,3-difluoropyridine. The DFT calculations have been carried out for the parent compounds and for a set of their 2-lithio, and variously substituted fluoro derivatives. The DFT data reproduced very well the experimental coupling values and revealed that the Fermi contact contribution is the dominating factor which governs the magnitude of the CC coupling across one bond.

Cyclic N-Oxides↗

PubMed1993

Ligand effects on platinum binding to DNA. A comparison of DNA binding properties for cis- and trans-[PtCl2(amine)2] (amine = NH3, pyridine).

The DNA binding properties of cis- and trans-[PtCl2(pyridine)2] have been examined and compared with their NH3 analogs, cis- and trans-DDP. The presence of a planar ligand reduces the rates of DNA binding but does not greatly affect the overall conformation of CT DNA, as measured by circular dichroism spectroscopy. The sequence specificity of trans-[PtCl2(py)2] includes alternating purine-pyrimidine sequences. The sequence specificity is further different between the two pyridine isomers, and the steric effects of two cis-pyridine groups are demonstrated by the appearance of relatively few binding sites in the 49-bp duplex. The effects of the pyridine ligand are further manifested by a greatly enhanced DNA-DNA interstrand cross-linking efficiency for the trans isomer, with a cross-link per adduct frequency of between 0.14 and 0.23, depending on the rb of the sample. The unwinding of closed circular pUC19 DNA by trans-[PtCl2(pyridine)2] is also more efficient than that by either DDP isomer, with an unwinding angle calculated at phi = 17 degrees (compare cis-DDP with phi = 13 degrees and trans-DDP with phi = 9-10 degrees). In contrast, little unwinding is induced by cis-[PtCl2(pyridine)2], with phi = 4 degrees. These results in particular invert the standard cis/trans structure-activity relationships observed previously for [PtCl2(NH3)2]. The results are discussed with respect to the previously demonstrated effect of activation of the trans-platinum geometry using sterically hindered ligands.

Base Sequence↗

PubMed2004

Tetra-2,3-pyrazinoporphyrazines with externally appended pyridine rings. 1. Tetrakis-2,3-[5,6-di(2-pyridyl)pyrazino]porphyrazine: a new macrocycle with remarkable electron-deficient properties.

A new pyrazinoporphyrazine macrocycle carrying externally appended pyridine rings, tetrakis-2,3-[5,6-di(2-pyridyl)pyrazino]porphyrazine (hydrated), [Py(8)TPyzPzH(2)].2H(2)O, was prepared in high yield by direct cyclotetramerization of the precursor, 2,3-dicyano-5,6-di(2-pyridyl)-1,4-pyrazine, [(CN)(2)Py(2)Pyz], in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). The single-crystal X-ray structure of [(CN)(2)Py(2)Pyz] shows a noncoplanar positioning of the pyrazine and pyridine rings in the two slightly different independent molecular units present in the crystal. UV-vis spectra of [Py(8)TPyzPzH(2)] were measured in two nondonor solvents (CHCl(3), CH(2)Cl(2)), a slightly basic solvent (pyridine), and an acidic solvent (CH(3)COOH). In all cases, the spectral changes are consistent with the occurrence of molecular aggregation and colloidal dispersions which break up with time to give clear solutions containing exclusively the monomeric form of the macrocycle, either neutral [Py(8)TPyzPzH(2)] (in CHCl(3), CH(2)Cl(2), and CH(3)COOH) or dianionic [Py(8)TPyzPz](2)(-) (in pyridine). A spectrally monitored titration of [Py(8)TPyzPzH(2)] in CH(2)Cl(2) with TBA(OH) shows the loss of two protons from the macrocyclic core and quantitative conversion of [Py(8)TPyzPzH(2)] to [Py(8)TPyzPz](2)(-). Cyclic voltammetry and thin-layer spectroelectrochemical measurements show that [Py(8)TPyzPzH(2)] is present in CH(2)Cl(2) while [Py(8)TPyzPz](2)(-) is present in pyridine, but both forms of the compound exhibit identical electrochemical behavior, consistent with a conversion of the dianion to the neutral porphyrazine in pyridine prior to electroreduction via four reversible one-electron transfer steps. No oxidations of the macrocycle are observed in either solvent containing 0.1 M tetrabuthylammonium perchlorate (TBAP). A comparison of the electrochemical behavior for [Py(8)TPyzPzH(2)] with what is reported for related phthalocyanine and porphyrazine analogues highlights the remarkable electron-accepting properties of the presently investigated free-base macrocycle.

Journal Article↗

PubMed2002

Selective preparation of pyridines, pyridones, and iminopyridines from two different alkynes via azazirconacycles.

Selective preparation of pyridine derivatives from two different alkynes and a nitrile was achieved by a novel procedure in which an alkyne and a nitrile couple first to give an azazirconacyclopentadiene followed by reaction with the second alkyne in the presence of 1 equiv of NiCl(2)(PPh(3))(2). This procedure gives only single products of pyridine derivatives from two different symmetrical alkynes and a nitrile. Our novel procedure can be used even with two similar alkyl-substituted alkynes such as 3-hexyne and 4-octyne. Two possible pyridine isomers from 3-hexyne, 4-octyne, and acetonitrile could be completely and independently prepared as single products by this method. The origin of the selectivity comes from the addition order of two different alkynes. This method was applied for the formation of pyridones and iminopyridines using isocyanate and carbodiimide derivatives instead of nitriles, respectively. Reaction of an alkyne with Cp(2)ZrEt(2) and an isocyanate or a carbodiimide gives an azazirconacycle. Treatment of the azazirconacycle with the second alkyne in the presence of 1 equiv of NiCl(2)(PPh(3))(2) gave a pyridone or an iminopyridine derivative. The use of two different unsymmetrical alkynes afforded the pyridine with five different substituents when the first alkyne has a trialkylsilyl group and the second alkyne has a phenyl group as functional groups. On the other hand, azazirconacyclopentadienes reacted with propargyl bromide in the presence of CuCl with excellent regioselectivity to give tetrasubstituted pyridine derivatives as single products. With the assistance of the trialkylsilyl groups, pyridines with all different substituents including H were also prepared.

Journal Article↗

PubMed2003

Formation of highly ordered organic monolayers by dative bonding: pyridine on ge(100).

The adsorption of pyridine onto the Ge(100) surface has been studied using both real-time scanning tunneling microscopy (STM) and ab initio pseudopotential density functional calculations. The results show that pyridine molecules adsorb on the electron-deficient down-Ge atoms of the Ge=Ge dimers via Ge-N dative bonding, with the pyridine ring tilted to the surface. The electron-rich up-Ge atoms remaining after adsorption of pyridine induce an asymmetric dimer row, which is mainly reconstructed to the c(4 x 2) structure. At pyridine coverage of 0.25 ML, the adsorbed pyridine molecules form a perfectly ordered monolayer. The entire Ge substrate underlying this organic monolayer rearranges into the c(4 x 2) structure.

Journal Article↗

PubMed1985

Structure-activity relationships of arylimidazopyridine cardiotonics: discovery and inotropic activity of 2-[2-methoxy-4-(methylsulfinyl)phenyl]-1H-imidazo[4,5-c]pyridine.

Recently several noncatecholamine, nonglycoside cardiotonic drugs have been discovered that possess both inotropic and vasodilator activities in experimental animals and man. Prototypical compounds include amrinone, sulmazole, and fenoximone. We investigated the structural requirements necessary for optimal inotropic activity in a series of molecules containing a heterocyclic ring fused to 2-phenylimidazole and discovered that 2-phenylimidazo[4,5-c]pyridines were generally 5-10-fold more potent than analogous 2-phenylimidazo[4,5-b]pyridines (e.g., sulmazole) or 8-phenylpurines. Furthermore, all imidazo[4,5-c]pyridine analogues we tested were orally active; in contrast, only one of the imidazo[4,5-b]pyridine derivatives, sulmazole, was significantly active. One of several highly active compounds in the [4,5-c] series was 50 (LY175326, 2-[2-methoxy-4-(methylsulfinyl)phenyl]-1H-imidazo[4,5-c]pyridine hydrochloride). The structure-activity relationship of this series is presented and compared to that of the imidazo[4,5-b]pyridine and purine series.

Animals↗

PubMed1965

The formation of pyridine haemochromogen.

1. Titration of haem with pyridine in alkaline media of low ionic strength yields a true pyridine haemochromogen, compound III, at very low concentrations of pyridine. 2. Graphical analysis of this titration gives the first spectrophotometric evidence for a dimeric haem. 3. Compound III is unstable and tends to aggregate to a second compound, compound II, whose formation is enhanced under those conditions favourable to hydrophobic bonding. 4. At higher concentrations of pyridine, compound II is dispersed to yield the classical pyridine haemochromogen, compound I, whose spectral properties are essentially those of pyridine haemochromogen in a non-aqueous medium.

Journal Article↗

PubMed1978

Regulation of Ca2+ release from mitochondria by the oxidation-reduction state of pyridine nucleotides.

Mitochondria from normal rat liver and heart, and also Ehrlich tumor cells, respiring on succinate as energy source in the presence of rotenone (to prevent net electron flow to oxygen from the endogenous pyridine nucleotides), rapidly take up Ca(2+) and retain it so long as the pyridine nucleotides are kept in the reduced state. When acetoacetate is added to bring the pyridine nucleotides into a more oxidized state, Ca(2+) is released to the medium. A subsequent addition of a reductant of the pyridine nucleotides such as beta-hydroxybutyrate, glutamate, or isocitrate causes reuptake of the released Ca(2+). Successive cycles of Ca(2+) release and uptake can be induced by shifting the redox state of the pyridine nucleotides to more oxidized and more reduced states, respectively. Similar observations were made when succinate oxidation was replaced as energy source by ascorbate oxidation or by the hydrolysis of ATP. These and other observations form the basis of a hypothesis for feedback regulation of Ca(2+)-dependent substrate- or energy-mobilizing enzymatic reactions by the uptake or release of mitochondrial Ca(2+), mediated by the cytosolic phosphate potential and the ATP-dependent reduction of mitochondrial pyridine nucleotides by reversal of electron transport.

Adenosine Triphosphate↗

PubMed1974

Activation of the de novo pathway for pyridine nucleotide biosynthesis prior to ricinine biosynthesis in castor beans.

The ricinine content of etiolated seedlings of Ricinus communis increased nearly 12-fold over a 4-day period. In plants quinolinic acid is an intermediate in the de novo pathway for the synthesis of pyridine nucleotides. The only known enzyme in the de novo pathway for pyridine nucleotide biosynthesis, quinolinic acid phosphoribosyltransferase, increased 6-fold in activity over a 4-day period which preceded the onset of ricinine biosynthesis by 1 day. The activity of the remainder of the pyridine nucleotide cycle enzymes in the seedlings, as monitored by the specific activity of nicotinic acid phosphoribosyltransferase and nicotinamide deamidase, was similar to that found in the mature green plant. In the roots of Nicotiana rustica, where the pyridine alkaloid nicotine is synthesized, the level of quinolinic acid phosphoribosyltransferase was 38-fold higher than the level of nicotinic acid phosphoribosyltransferase, whereas in most other plants examined, the specific activity of quinolinic acid phosphoribosyltransferase was similar to the level of activity of enzymes in the pyridine nucleotide cycle itself. A positive correlation therefore exists between the specific activity of a de novo pathway enzyme catalyzing pyridine nucleotide biosynthesis in Ricinus communis and Nicotiana rustica and the biosynthesis of ricinine and nicotine, respectively.

Journal Article↗

PubMed1994

Pyridine nucleotide redox potential modulates cystic fibrosis transmembrane conductance regulator Cl- conductance.

Cl- conductance of the apical membrane of airway epithelial cells has properties of a passive diffusion mechanism but is decreased by inhibition of oxidative metabolism. Recent reports that cAMP-dependent Cl- conductance also requires ATP at the intracellular domains of the cystic fibrosis transmembrane conductance regulator (CFTR) suggests that ATP concentration could mediate metabolic regulation of Cl- conductance. However, metabolic inhibitors affect processes other than ATP free energy levels, including notably the metabolic pathways that set the redox potential of pyridine nucleotides within the cell. We have investigated the possibility that CFTR-mediated Cl- conductance is affected by the ratio of oxidized to reduced intracellular pyridine nucleotides. CFTR was expressed in airway and heterologous cells and studied under whole cell voltage clamp conditions, which permitted the intracellular NAD(P)+/NAD(P)H ratio to be varied independently of ATP concentration. In three cell types expressing CFTR, whole cell dialysis with reduced pyridine nucleotides inhibited activation of Cl- currents by forskolin and 8-(4-chlorophenylthio)-cAMP (CPT-cAMP), whereas dialysis with oxidized pyridines increased both basal and stimulated CFTR-mediated Cl- conductance. In cell-attached membrane patches, the open probability of 5-6-picosiemens Cl- channels that had been activated by forskolin and CPT-cAMP was further and reversibly increased by permeant oxidants. Neither swelling-induced whole cell K+ currents in CFTR-expressing cells nor swelling-induced whole cell Cl- currents in multidrug resistance protein-expressing cells were affected by NADPH. Pyridine nucleotide redox potential had little effect on phosphorylation of histone by protein kinase A. We conclude that CFTR Cl- conductance function can be modulated by pyridine nucleotide redox potential. This effect points to the existence of a mechanism or mechanisms by which cytosolic nucleotides other than ATP can affect plasma membrane Cl- conductance and may help explain how a passive ion conductance is linked to cellular energy metabolism.

3T3 Cells↗

PubMed1986

Antitumor and immunologic effects of a pyridine-extracted fraction of Propionibacterium acnes.

The antitumor and immunological effects of a pyridine extractable fraction of Propionibacterium acnes were tested in a murine ovarian teratocarcinoma (MOT) model. Previous studies have demonstrated that tumor rejection in this model depends upon sequential activation of tumoricidal neutrophils (PMNs) followed by cytostatic macrophages. The pyridine extract significantly prolonged the survival of mice challenged with 10(3) or 10(4) MOT cells but had little impact on a 10(5) tumor inoculum. In vivo cytoreduction occurred within the first 24 h following IP treatment which correlated temporally with the influx of tumoricidal PMNs into the peritoneal cavity. Immunotherapy failure in mice challenged with 10(5) MOT cells occurred between 48 and 72 h after treatment when macrophage chemotaxis into the peritoneal cavity was initiated. Although injection of unfractionated bacteria activated MOT-cytostatic macrophages, the pyridine extract was deficient in this regard. Intraperitoneal injection of the pyridine extract resulted in an early (day +1) depression and late (day +5) enhancement of peritoneal NK cytotoxicity. These data suggest that the retention of neutrophil-activating moieties in the pyridine extract are sufficient for antitumor effects against low tumor inocula while the depletion of macrophage-activating determinants results in diminished effects against larger tumor cell challenges.

Adjuvants, Immunologic↗

PubMed1981

Effect of pyridine homologues on the basal rate of electron transport and H+/e- ratio in chloroplasts.

Low concentrations of hydrophobic pyridine homologues (1 mM) were found to increase the rate of the Hill reaction in chloroplasts without significantly affecting either the steady-state proton uptake or the rate of proton leakage in the dark. By assuming that the organic base can be bound to two types of independent binding sites in the thylakoid membrane with dissociation constants K1 and K2 respectively, the kinetic data can be treated quantitatively. The values of K1 and K2 determined by the treatment are in the same relative order as the hydrophobicities of the pyridine homologues: K1 - 1.16 mM and K2 = 54 mM for pyridine; 0.6 and 38 mM for 4-picoline; 0.27 and 31 mM for 4-ethylpyridine, 0.10 and 4.2 mM for 4-t-butylpyridine; 0.08 and 3.2 mM for 4-n-butylpyridine. The rates of oxygen generation and proton uptake by illuminated chloroplasts with either ferricyanide or 1,4-benzoquinone as the electron acceptor were also measured in the presence of various pyridine homologues. Low concentration of pyridine homologues were found to decrease the H+/e- ratio. This last observation seems to substantiate an indirect coupling mechanism between electron transport and proton translocation.

Chloroplasts↗

PubMed1992

Evidence for elevation of cytochrome P4502E1 (alcohol-inducible form) mRNA levels in rat kidney following pyridine administration.

The effects of pyridine on renal cytochrome P4502E1 (CYP2E1) expression in rat have been examined by immunoblot and Northern blot analyses. Immunoblot analyses revealed that 2E1 protein levels were elevated from 1.4- to 4.6-fold following pyridine administration in a dose- and time-dependent manner. Northern blot analyses revealed that renal 2E1 poly(A)+ RNA levels increased from 1.4- to 3.8-fold following pyridine treatment and that these increases in 2E1 mRNA paralleled the dose- and time-dependent increases in 2E1 protein content. In contrast, hepatic 2E1 poly(A)+ RNA levels failed to increase following these same dosing regimens, suggesting that metabolic alterations, such as those associated with starvation, were not etiologic factors in renal 2E1 induction. These results show that pyridine induced CYP2E1 in kidney and that elevation of renal 2E1 protein levels accompanying pyridine administration occurred at least partly as a consequence of increased 2E1 poly(A)+ RNA levels. The results of this research reveal that regulatory mechanisms governing CYP2E1 expression may differ in hepatic and renal tissues.

Animals↗

PubMed1978

Pyridine interactions with phenolic groups in water: evidence for hydrogen bonding and hydrophobic association.

Pyridine interactions with phenol, substituted phenol, tyrosine and poly(Glu50,Tyr50) in aqueous solutions have been studied by ultraviolet (UV) difference spectroscopy, spectrophotometric pH titration, circular dichroism (CD) and proton magnetic resonance (PMR) spectroscopy. A red shift and spectral sharpening of the near-UV spectrum of phenol in water was noted at pyridine concentrations greater than 0.25 M. In addition, the spectrophotometric equivalence point for the phenol- or substituted phenol-phenolate equilibrium was increased about 0.5 pH units upon the addition of 1.0 M pyridine. PMR studies were consistent with the formation of a 1 : 1 phenol-pyridine hydrogen bonded complex. The equilibrium constant derived for this interaction, 0.6-0.7 M-1, is greater than the corresponding value for phenol-acetate hydrogen bonding in water. Enhancement of thepyridine hydrogen bond interaction with Tyr within poly(Glu50,Tyr50) was observed at pH greater than 12 due to a hydrophobic microenvironment produced by pyridine molecules intercalating between neighboring tyrosyl residues.

Circular Dichroism↗