Relationship of metabolism of 2′-, 3′- and 5′-adenine nucleotides to presynaptic inhibition of transmitter release in rat vas deferens

Summary In the isolated rat vas deferens stimulated at 0.2 Hz, a series of 2, 3-, and 5-substituted adenine nucleotides all inhibited the twitch responses, their actions being potentiated by the nucleoside transport inhibitors, HNBTGR, NBMPR and dipyridamole.The metabolism of these nucleotides was examined utilising HPLC analysis of the bathing medium after exposure to 30 M nucleoside or nucleotide for 5 min. 5-AMP, 5-ADP, 5-ATP, and NAD⁺ were all partially hydrolysed to adenosine, the relative extent of this being 5-AMP>5-ADP=5-ATPNAD⁺. However, the other nucleotides examined were not detectably converted to adenosine or to adenosine deamination products.These results indicate that the 2-, 3- and 5-substituted nucleotides studied act at a P₁-purinoceptor in rat vas deferens to inhibit neurotransmission and, with the exception of 5-AMP, 5-ADP, 5-ATP and NAD⁺, all appear to act directly at this receptor. However, the 5-adenine nucleotides (AMP, ADP and ATP) and NAD⁺ all appear to act at least partially indirectly subsequent to their hydrolysis to adenosine.Abbreviations. The following abbreviations are used ADA adenosine deaminase (EC 3.5.4.4) - 5-ADP adenosine 5-diphosphate - 2,5-ADP adenosine 2,5-diphosphate - 3 5-ADP, adenosine 3,5-diphosphate - 2-, 3 or 5-AMP adenosine 2-, 3-, or 5-monophosphate - 5-ATP adenosine 5-triphosphate - cNADP⁺ -nicotinamide dinucleotide 2,3-cyclic monophosphate - CoA coenzyme A - HNBTGR 6-(2-hydroxy-5-nitrobenzyl)-thioguanosine - NAD⁺ -nicotinamide adenine dinucleotide - NADP⁺ -nicotinamide adenine dinucleotide phosphate - NBMPR 6-(4-nitrobenzylthio)-purine riboside     

Studies on the constituents of Scutellaria species (XXI): constituents of the leaves of Scutellaria strigillosa Hemsley

From the leaves of Scutellaria strigillosa, 14 compounds, chrysin, apigenin, 5,7,2-trihydroxyflavone, norwogonin, ursolic acid, 6-hydroxy-4-stigmasten-3-one, 6-hydroxy-4,22-stigmastadien-3-one, 2 R,4 R,8 R--tocopherol, (S)-5,5 -bi--tocopheryl, (R)-5,5 -bi--tocopheryl, solanachromene, tocopherylquinone, jodrellin T, and 14,15-dihydrojodrellin T were isolated. The structures were determined on the basis of chemical and spectral data.     

Synthesis and Anti-inflammatory Effect of Chalcones and Related Compounds

Purpose. Mast cell and neutrophil degradations are the important players in inflammatory disorders. Combined with potent inhibition of chemical mediators released from mast cells and neutrophil degranulations, it could be a promising anti-inflammatory agent. 2,5-Dihydroxychalcone has been reported as a potent chemical mediator and cyclooxygenase inhibitor. In an effort to continually develop potent anti-inflammatory agents, a novel series of chalcone, 2- and 3-hydroxychalcones, 2,5-dihydroxychalcones and flavanones were continually synthesized to evaluate their inhibitory effects on the activation of mast cells and neutrophils and the inhibitory effect on phlogist-induced hind-paw edema in mice. Methods. A series of chalcones and related compounds were prepared by Claisen-Schmidt condensation of appropriate acetophenones with appropriate aromatic aldehyde and the anti-inflammatory activities of these synthetic compounds were studied on inhibitory effects on the activation of mast cells and neutrophils. Results. Some chalcones showed strong inhibitory effects on the release of -glucuronidase and histamine from rat peritoneal mast cells stimulated with compound 48/80. Almost all chalcones and 4-hydroxyflavanone exhibited potent inhibitory effects on the release of -glucuronidase and lysozyme from rat neutrophils stimulated with formyl-Met-Leu-Phe (fMLP). Some chalcones showed potent inhibitory effects on superoxide formation of rat neutrophils stimulated with fMLP/cytochalasin B (CB) or phorbol myristate acetate (PMA). 2,3-Dihydroxy-, 2,5-dihydroxy-4-chloro-, and 2,5-dihydroxychalcone showed remarkable inhibitory effects on hind-paw edema induced by polymyxin B in normal as well as in adrenalectomized mice. Conclusions. These results indicated that the anti-inflammatory effects of these compounds were mediated, at least partly, through the suppression of chemical mediators released from mast cells and neutrophils.     

The Solution Conformations of Lidocaine Analogues

IR and ¹H NMR studies in CDCl₃ and CCl₄ of a series of tertiary aminoxylidides with the amino group in the 2 to 6 position of the acyl chain are described. Lidocaine, diethylaminoaceto-2,6-xylidide, forms an intramolecular five-membered ring hydrogen-bonded monomer at all concentrations in both solvents. -Diethyl-amino-propiono-2,6-xylidide forms an intramolecular six-membered ring hydrogen-bonded monomer in CDCl₃ and CCl₄ but a trans intermolecularly associated species is the major form present at high concentrations in CCl₄. The longer-chain homologues are mixtures of nonassociated trans and cis monomers at low concentrations but associated trans forms predominate at high concentrations. Evidence for the presence of a hydrogen-bonded seven-membered ring intramolecular monomer in CDCl₃ for -diethylaminobutyro-2,6-xylidide is presented. The relationship between the molecular conformation and the partition coefficient is discussed.     

Trennung und Bestimmung der Nucleotide des Gehirns

Ohne ZusammenfassungFolgende Abkürzungen werden in der Arbeit verwendet AMP Adenosin-5-monophosphat - ADP Adenosin-5-diphosphat - ATP Adenosin-5-triphosphat - GMP Guanosin-5-monophosphat - GDP Guanosin-5-diphosphat - GTP Guanosin-5-triphosphat - IMP Inosin-5-monophosphat - UMP Uridin-5-monophosphat - UDP Uridin-5-diphosphat - UTP Uridin-5-triphosphat - UDPAG Uridin-5-diphosphat-N-acetylglucosamin - UDPG Uridin-5-diphosphat-glucose - DPN Diphosphopyridinnucleotid - TPN Triphosphopyridinnucleotid Mit 10 TextabbildungenMit Unterstütznng der Deutschen Forschungsgemeinschaft.     

Adrenocorticolytic DDT-metabolites: studies in mink,Mustela vison and otter,Lutra lutra

The irreversible binding and toxicity of the DDT metabolites p,p-DDD and o,p-DDD in the adrenal cortex of female mink Mustela vison were studied. Histological examination of adrenals from mink given a single i.p. injection of p,p-DDD or o,p-DDD (125 mg per kg body weight) showed vacuolation, necrosis and focal bleedings in the zonae fasciculata and reticularis. Autoradiograms of solvent-extracted tissue sections of minks given a single i.v. injection of p,p-[¹⁴C]DDD (0.7 mg per kg body weight) revealed a high level of irreversibly bound radio-activity in the adrenal cortex. Microautoradiography showed that the irreversibly bound radio-activity was confined to the zonae fasciculata and reticularis. Incubation of p,p-[¹⁴C]DDD and o,p-[¹⁴C]DDD with mink or otter, Lutra lutra, adrenal homogenate (300 x g supernatant) resulted in an irreversible binding of radioactivity to protein from both species. The irreversible protein binding of the DDD isomers in mink and otter was decreased by addition of the cytochrome P450 inhibitors metyrapone and carbon monoxide, indicating a cytochrome P450 dependent metabolic activation. In contrast, 3-methylsulfonyl-[¹⁴C]DDE, a potent adrenocortical toxicant in mice, does not appear to be metabolized to a reactive metabolite in the adrenal cortex of mink or otter. In conclusion, both p,p-DDD and o,p-DDD are toxic to the mink adrenal zona fasciculata and reticularis following activation in situ to reactive, tissue-binding metabolites. The results suggest that p,p-DDD and o,p-DDD are adrenocortical toxicants also in otter. The involvement of environmental pollutants in the generation of the adrenocortical hyperplasia observed among Baltic seals is discussed.Abbreviations p,p-DDD 2-(4-chlorophenyl)-2(4-chlorophenyl)-1,1-dichloroethane - o,p-DDD 2-(2-chlorophenyl)-2(4-chlorophenyl)-1,1-dichloroethane - MeSO₂-DDE 3-methylsulfonyl-2,2-bis(4-chlorophenyl)-1,1-dichloroethane - DDT 2-(4-chlorophenyl)-2-(4-chlorophenyl)-1,1,1-trichloroethane - GSH reduced glutathione - PCB polychlorinated biphenyls     

Further studies on (±)-YM-12617, a potent and selective α1-adrenoceptor antagonist and its individual optical enantiomers

Summary YM-12617, 5-[2-[[2-(o-ethoxyphenoxy)ethyl]amino]propyl]-2-methoxybenzenesulfonamide HCl is structurally novel, an extremely potent and highly selective ₁-adrenoceptor antagonist. An asymmetric center exists at the -carbon atom in the phenethylamine portion of YM-12617, therefore two optical enantiomers exist. -Adrenoceptor blocking properties and hypotensive activities of YM-12617 and its enantiomers have been compared in vitro and in vivo. 1. In the isolated rabbit aorta, R(–)- and S(+)-YM-12617 competitively antagonized phenylephrine-induced contraction with pA₂ values of 9.95 and 7.69, respectively. Although R(–)- and S(+)-YM-12617 were also competitive antagonists toward UK-14,304 at prejunctional ₂-adrenoceptors in the isolated guinea-pig ileum, the affinities of R(–)-YM-12617 (pA₂ = 6.18) and S(+)-YM-12617 (pA₂ = 5.64) for these receptors were 5,900 and 110 times lower than those displayed for postjunctional ₁-adrenoceptors in the isolated rabbit aorta. 2. R(–)- and S(+)-YM-12617 displaced both ³H-prazosin and ³H-idazoxan binding to rat brain membranes; however, the affinities of the R(–)- and S(+)-enantiomers for ₁-adrenoceptors (pK_i = 9.95 and 7.83, respectively) were 21,000 and 72 times higher than those for ₂-adrenoceptors (pK _i = 5.62 and 5.97), respectively. 3. Based on pA₂ values obtained in the isolated tissues and pK _i values in the binding assays, R(–)-YM-12617 was 132–182 times more potent than S(+)-YM-12617 as an antagonist at ₁-adrenoceptors. In contrast, the R(–)- and S(+)-enantiomers were similar in potency at blocking ₂-adrenoceptors. 4. In normotensive pithed rats, R(–)- and S(+)-YM-12617 preferentially antagonized the ₁-adrenoceptor mediated pressor effect of phenylephrine with DR₁₀ values of 1.38 and 705 g/kg i. v., respectively, although a high dose (3,000 g/kg i.v.) also inhibited the effect of UK-14,304 at postjunctional ₂-adrenoceptors. R(–)-YM-12617 exhibited an over 2,000-fold selectivity for postjunctional ₁-adrenoceptors, and R(–)-YM-12617 was over 500 times more potent than S(+)-YM-12617 in antagonizing postjunctional ₁-adrenoceptors based on DR₁₀ values. 5. In anesthetized rats, R(–)- and S(+)-YM-12617 dose-dependently produced hypotension with ED₂₀ values, doses required decreased mean blood pressure by 20%, of 0.64 and 61 g/kg i. v., respectively. R(–)-YM-12617 exerted a 95 times more potent hypotensive activity than S(+)-YM-12617, and its isomeric activity ratio was consistent with that for ₁-adrenoceptors but not ₂-adrenoceptors. 6. The present results suggest that the high stereoselectivity of the optical enantiomers of YM-12617 is in the ₁-adrenoceptor, but not in the ₂-adrenoceptor, and their antagonist potency for ₁-adrenoceptors is likely to contribute to the hypotensive effect. Send offprint requests to K. Honda     

Metabolism and presynaptic inhibitory activity of 2′,3′ and 5′-adenine nucleotides in rat vas deferens

Summary In the isolated rat vas deferens stimulated at 0.2 Hz, [¹⁴C]labelled 5-AMP, 5-ADP and 5-ATP (10 M) inhibited twitch responses, were broken down to [¹⁴C]adenosine in the medium and incorporated into [¹⁴C]adenine ribonucleotides in the tissue. Pretreatment of tissues with 6-(2-hydroxy-5-nitrobenzyl)-thioguanosine (NBTGR), a potent inhibitor of adenosine transport, potentiated the presynaptic inhibitory action of these 5 nucleotides and reduced their incorporation in [¹⁴C]adenine nucleotides, but did not alter the appearance of [¹⁴C]adenosine in the medium.A series of 2, 3 and 5-substituted adenine nucleotides (10 M) inhibited the twitch responses of the vas deferens stimulated at 0.2 Hz. This effect was potentiated by NBTGR. Addition of exogenous adenosine deaminase very significantly reduced the inhibitory actions of adenosine, 5-AMP, 5-ADP and 5-ATP and also reduced those of 2, 5-ADP, NAD⁺ and dePCoA. The inhibitory actions of the other 2, 3 and 5 adenine nucleotides studied were not altered by exogenous adenosine deaminase.These results indicated that the presynaptic inhibitory actions of 5-AMP, 5-ADP and 5-ATP in rat vas deferens predominantly result from their prior hydrolysis to adenosine whereas the 2, 3 and 5-substituted adenine nucleotides appear to act mainly directly to inhibit transmitter release.Abbreviations. The following abbreviations are used 5-ADP 5-adenosine diphosphate - 2,5-ADP 2,5-adenosine diphosphate - 3,5-ADP 3,5-adenosine diphosphate - 2,3 or 5-AMP 2,3 or 5-adenosine monophosphate - 5-ATP 5-adenosine triphosphate - CoA coenzyme A - 2,3-cAMP 2,3-cyclic adenosine monophosphate - cNADP⁺ -nicotinamide dinucleotide 2,3-cyclic monophosphate - dePCoA dephosphocoenzyme A - NAD⁺ -nicotinamide adenine dinucleotide - NADP⁺ -nicotinamide adenine dinucleotide phosphate - NBTGR 6-(2-hydroxy-5-nitrobenzyl)-thioguanosine - oxid CoA oxidized-coenzyme A     

Presynaptic opioid receptors modulating acetylcholine release in the hippocampus of the rabbit

Summary Inhibition of cardiae adenylate cyclase by adenosine receptor agonists was reinvestigated in a more homogeneous sarcolemmal vesicular preparation than used in a previous study. Microsomal particles obtained by differential centrifugation were further fractionated on a shallow density gradient of Percoll. Two populations of plasma membrane vesicles were partially resolved. Identical peaks were identified for adenylate cyclase activity and [³H]ouabain binding, whereas 5-nucleotidase activity and -adrenoceptor binding displayed an additonal peak at higher density, where angiotensin converting enzyme, a marker for endothelial plasma membranes, was at maximal activity. Significant inhibition by N⁶-cyclohexyladenosine (CHA), as measured in each fractionation step following homogenization, was observed only at the activity peak of adenylate cyclase. Moreover, analysis of the degree and rank order of potency of several adenosine analogs was indicative for interaction with A₁-adenosine receptors. Accordingly, the peak in adenosine receptor binding, using (-)[¹²⁵I]iodo-N⁶-hydroxyphenyl-isopropyladenosine as the radioligand, coincided with CHA-inhibitable adenylate cyclase activity. By contrast, adenylate cyclase was slightly stimulated by CHA in the higher density range, an action suggested to be mediated via A₂-adenosine receptors, which recently have been demonstrated to exist on guinea-pig coronary endothelium. It is concluded that the full extent of adenosine receptor-mediated adenylate cyclase inhibition in the heart is only to be demonstrated if contamination of the sarcolemmal preparation with endothelial membrane components is kept to a minimum.Abbreviations R-PIA (–)N⁶-(R-phenylisopropyl)-adenosine - NECA 5-(N-ethyl-carboxamido)-adenosine - ICYP (–)[¹²⁵I]iodo-cyanopindolol - dATP 2-deoxy-adenosine-5-triphosphate - S-PIA (+)N⁶-(S-phenylisopropyl)-adenosine - HPIA (–)N⁶-(4-hydroxy-phenylisopropyl)-adenosine - CHA N⁶-cyclohexyl-adenosine - Gpp(NH)p guanylyl imidodiphosphate - dAMP 2-deoxy-adenosine-5-monophosphate - HEPES 4-(2-hydroxyethyl)-1-piperazineethane-sulfonic acid - EDTA (ethylenedinitrilo)-tetraacetic acid - [¹²⁵I]HPIA (–)N⁶-(3-[¹²⁵I]-iodo-4-hydroxyphenylisopropyl)-adenosine     

Lysergic acid diethylamide antagonizes shaking induced in rats by five chemically different compounds

Thyrotropin-releasing hormone (TRH), sodium valproate, AG-3-5 (1-[2-hydroxyphenyl]-4-[3-nitrophenyl]-1,2,3,6-tetrahydropyrimidine-2-one), RX336-M (7,8-dihydro-5, 6-dimethylcyclohex-5-eno-1,2,8,14 codeinone), and Sgd 8473 (-[(4-chlorobenzylideneamino)-oxy]-isobutyric acid) each induced repetitive shaking of the body of rats after intraperitoneal injection. This action of the five diverse chemicals appears to be subserved by a common pharmacological component, because pretreatment with d-lysergic acid diethylamide (0.03–1.0 mg kg^-1, s.c.) attenuated the shaking behavior in a dose-related manner, and cross tolerance was found between RX 336-M and TRH, sodium valproate, and AG-3-5.     

Synthesis and transformations of furan derivatives

By the reactions of 2-phenyl-4-(2-furfuryliden)-, 2-phenyl-4-(5-nitro-2-furfuryliden)-, and 2-methyl-4-(5-nitro-2-furfuryliden)-5-oxazolones with primary and secondary amines, a series of N-mono- and N,N-disubstituted amides of the corresponding-benzamido--(2-furyl)-acrylic and-benzamido- and-acetamido--(5-nitro-2-furyl)acrylic acids was synthesized. 1-Alkyl(aryl) substituted 2-phenyl-4-(5-nitro-2-furfuryliden)-5-imidazolones were synthesized from the reaction of phosphorus oxychloride and the monosubstituted amides of-benzamido--(5-nitro-2-furyl)acrylic acid.Translated from Khimiko-Farmatsevticheskii Zhurnal, No. 2, pp. 21–27, February, 1967.     

Wirkung von cyclischem Adenosin-3′,5′-Monophosphat (3′,5′-AMP) und seinem Dibutyrylderivat (DBA) auf Lipolyse,Glykogenolyse und Corticosteronsynthese

Zusammenfassung 1. Am isolierten Fettgewebe von Ratten hatte das Dibutyrylderivat des cyclischen Adenosin-3,5-Monophosphat (DBA) eine etwa 100 mal stärkere lipolytische Wirkung als das nicht substituierte cyclische Adenosin-3,5-Monophosphat (3,5-AMP). Hormone (ACTH, Noradrenalin) waren an diesem Testobjekt 10000 mal wirksamer als DBA. Durch Hemmung der Phosphodiesterase mit Theophyllin ließ sich auch die Wirkung des DBA verstärken.2. An isolierten Nebennieren von Ratten stimulierte DBA die Corticosteronsynthese etwa 100 mal stärker als 3,5-AMP; ACTH war aber 500 mal wirksamer als DBA. Durch Theophyllin ließ sich die Wirkung von ACTH, DBA bzw. 3,5-AMP nicht verstärken. Hohe Konzentrationen des Xanthinderivates hemmten die Corticosteronsynthese.3. An Ratten war die hyperglykämische Wirkung des DBA wesentlich stärker als diejenige des 3,5-AMP: Für eine Erhöhung des Blutzuckerspiegels um 40 mg/100 ml benötigten wir von DBA weniger als 1 mol/kg, von 3,5-AMP aber 30 mol/kg. Diese Wirkung der Nucleotide ließ sich durch Theophyllin nicht verstärken. Der Fettsäuren- und Glyceringehalt des Plasmas wurde durch Injektion von DBA bzw. 3,5-AMP nicht erhöht, sondern erniedrigt. — Die Ergebnisse wurden im Zusammenhang mit dem Second Messenger Concept von Sutherland u. Mitarb. diskutiert.Über einen Teil der Ergebnisse wurde auf der 8. Frühjahrstagung der Deutschen Pharmakologischen Gesellschaft (Stock u. Westermann, 1967; Bieck u. Westermann, 1967) sowie in einer kurzen Mitteilung (Bleck et al., 1968) berichtet.     

lontophoretic Delivery of a Telomeric Oligonucleotide

Purpose. To evaluate the feasibility of iontophoretically enhanced transdermal delivery of a phosphorothioate oligonucleotide across hairless mouse skin. Methods. The phosphorothioate sequence, 5-d(TTAGGG)-3 (TAG-6) which mimics the repeat sequence of the telomere was used as a model compound. Iontophoresis was performed on hairless mouse skin using an in vitro flow-through diffusion system. Both 5-FITC and uniformly ³⁵S labeled oligonucleotide were used to monitor transdermal flux. Results. Cathodal delivery of TAG-6 resulted in substantial oligonucleotide flux. The molecular label did not alter transport properties. No flux was measured with either anodal or passive delivery. The oligonucleotide was not degraded as it crossed the skin. Molecular transport was donor condition dependent, with pH and salt concentration both having significant effects. Pre-treating the skin with ethanol reduced iontophoretic transport. Conclusions. These data demonstrate that iontophoresis can enhance transdermal flux of an intact phosphorothioate oligonucleotide and that this penetration is donor condition dependent. Furthermore, iontophoretically enhanced transdermal delivery is a feasible apprach to the administration of phosphorothioate oligonucleotides.     

Effect of six virustatic nucleoside analogues on the development of fetal rat thymus in organ culture

The effects of the virustatic agents zidovudine (azidothymidine, AZT) 23-dideoxycytidine (ddC), 23-dideoxyinosine (ddI), acyclovir (ACV), ganciclovir (GCV), and vidarabine phosphate (VP) on the in vitro development of thymic lobes of 17-day-old rat fetuses were tested in an organ culture system. The virustatics were added to the medium for a culture period of 7 days. All nucleoside analogues inhibited the proliferation and differentiation of lymphatic cells. However, differences were observable with respect to the potency of the six drugs to interfere with thymic development. Compared to untreated controls, reduction in the number of thymocytes was significant at concentrations of 30 M AZT and ddI. In the case of ACV, GCV, VP, and ddC concentrations as low as 10 M were sufficient to cause a significant reduction, ddC being the most potent derivate. Increasing concentrations of the nucleoside analogues led to a dose-dependent further inhibition of cell proliferation. At a concentration of 30 M flow cytometry revealed a decrease in the relative number of double positive CD4⁺ CD8⁺ and single positive CD4⁺ CD8^– cells but an increase in the relative number of CD4-CD8⁺ cells. At the same concentration the expression of the CD5 antigen was reduced by the antimetabolites, indicating that maturation of the thymocytes was inhibited. Distribution of the forward light scatter, a cell size-related parameter, showed that the formation of small thymocytes was reduced by the nucleoside analogues. Light and electron microscopic investigations indicated cytotoxic effects of the drugs on the thymocytes, whereas the epithelium was only slightly affected.     

Immunomodulatory effect and quantitation of a cytotoxic glycosphingolipid from Murdannia loriformis

NMR signal reassignments for a cytotoxic glycosphingolipid compound, 2, -O-D-glucopyranosyl-2-(2-hydroxy-Z-6-enecosamide)sphingosine, isolated from an ethanolic extract of the herb Murdannia loriformis, have been achieved by use of FAB-MS, and 1D and 2D ¹H and ¹³C NMR. The amount of 2 in the herb juice was quantitatively determined by use of a validated HPLC method (RP-18, MeOH–H₂O, UV detection at 210 nm). The immunomodulatory effect of the herb juice and of 2 was proved by means of in vitro cellular immunological assays. Compound 2 at a concentration of 13 nmol L^–1 stimulated PBMC proliferation and increased the CD 3,4:CD 3,8 ratio in T lymphocytes.     

Effects of indomethacin on changes in renal blood flow induced by adenosine and its analogues in conscious dogs

Summary The effects of indomethacin on changes in renal blood flow induced by adenosine, NECA (adenosine-5-N-ethyl-carboxamide) and 2,3-dinitro-NECA were investigated in 6 chronically instrumented conscious dogs. Adenosine (187.5, 375 and 750 nmol/kg, i.v.) induced a dose-dependent initial decrease, followed by a reactive increase in renal blood flow. NECA (1.5 nmol/kg, i.v.) also induced an initial decrease, which was, however, followed by a prolonged reactive increase in renal blood fow. 2,3-dinitro-NECA (50 nmol/kg, orally) induced only an increase in renal blood flow. Indomethacin (27.9 mol/kg, i.v.) caused no relevant change of the initial decrease and a significant attenuation of the reactive increase in renal blood flow induced by adenosine. NECA-induced changes in blood flow were affected by indomethacin in the same direction but to a greater extent than were adenosine-induced changes in blood flow. Indomethacin reversed the increase to a decrease in renal blood flow induced by 2,3-dinitro-NECA. Thus, prostaglandins seem to be involved in mediating the response of renal blood flow to adenosine, NECA and 2,3-dinitro-NECA.Part of this study was presented at the fall meeting of the German Pharmacological Society, September 1982 in Vienna, Austria     

Identification of a novel high affinity adenosine binding protein from bovine striatum

Summary In solubilized extracts from bovine striatal membranes three different binding sites for 5-N-ethylcarboxamidoadenosine ([³H]NECA) were observed after separation of the extract by gel filtration on Sepharose CL-6B. The first peak was eluted in the void volume and contained the AZ adenosine receptor. In the second peak, [³H]NECA binding sites were eluted with a pharmacological profile characteristic of adenotin, a low affinity non-receptor adenosine binding protein. The third peak represented approximately 50% of the [³H]NECA binding activity. This site bound [³H]NECA in a reversible and saturable manner with K _D of 17 nmol/l and a binding capacity of 11.3 pmol/mg protein. In competition experiments, adenosine, NECA, NAD, nnosine, 5-AMP and S-adenosyl-L-homocysteine were the most potent ligands. In contrast to adenosine receptors, this site did neither bind adenosine receptor antagonists nor the A₂ selective agonist CGS 21,680 (2-[p-(2-carboxyethyl)phenethylamino]5-N-ethylcarboxamidoadenosine). These results suggest the existence of a novel high affinity binding site for adenosine of unknown function in bovine striatum.Abbreviations AMPPCP ,-methyleneadenosine-5-triphosphonate - CCPA 2-chloro-N⁶-cyclopentyladenosine - CHAPS 3-[3-(cholamidopropyl)dimethylammonio]-1-propanesulfonate - CGS 21,680 2-[p-(2-carboxyethyl)phenethylamino]-5-N-ethylcarbox-amidoadenosine - CPA N⁶-cyclopentyladenosine - DPCPX 1,3-dipropyl-8-cyclopentylxanthine - GppNHp guanosine-5-[,-imido]triphosphate - GTP[S] guanosine-5-O-(3-thiotriphosphate) - NBTI S-4-nitrobenzyl-6-thioinosine - NECA 5-N-ethylcarbox-amidoadenosine - NECG 5-N-ethylcarboxamidoguanosine - PIA N⁶-phenylisopropyladenosine - SAH S-adenosyl-L-homocysteine - XAC 8-{4-[([{(2-aminoethyl)-amino}carbonyl]-methyl)oxy]-phenyl}-1,3-dipropylxanthine Send offprint requests to A. Lorenzen at the above address     

[3H]5′-N-ethylcarboxamide adenosine binds to both Ra and Ri adenosine receptors in rat striatum

Summary Adenosine analogs such as 5-N-ethylcarboxamide adenosine and N⁶-cyclohexyladenosine stimulate or inhibit adenosine cyclase activity in preparations of rat striatum depending on the assay conditions. N⁶-cyclohexyladenosine inhibits but does not stimulate adenosine cyclase activity in preparations of hippocampus. These findings suggest that the striatum contains both R _a (stimulatory) and R _i (inhibitory) adenosine receptors while the hippocampus contains only R _i receptors. We have previously shown that [³H]N⁶-cyclohexyladenosine binds to R _i receptors in rat hippocampus (Yeung and Green 1983). Comparisons of the characteristics of [³H]5-N-ethylcarboxamide adenosine and [³H]N⁶-cyclohexyladenosine binding to hippocampus show that [³H]5-N-ethylcarboxamide adenosine also binds to R _i receptors with high affinity. [³H]5-N-ethylcarboxamide adenosine binds to R _i receptors in the striatum and to a second site that is present in striatum but not hippocampus. High affinity binding of both ligands to R _i receptors can be blocked by treatments with N-ethylmaleimide that do not markedly affect [³H]5-N-ethylcarboxamide adenosine binding to the second site in the striatum. The pharmacological characteristics of the second site indicate that it is the R _a adenosine receptor.The abbreviations used are NEM N-ethylmaleimide - Gpp(NH)p 5-guanylylimidodiphosphate - NECA 5-N-ethylcarboxamide adenosine - l-PIA N⁶-(l-phenylisopropyl)adenosine - d-PIA N⁶-(d-phenylisopropyl) adenosine - DPX 1,3-diethyl-8-phenylxanthine     

Immobilized Artificial Membrane (lAM)-HPLC for Partition Studies of Neutral and Ionized Acids and Bases in Comparison with the Liposomal Partition System

Purpose. To study the partitioning of model acids ((RS)-warfarin and salicylic acid), and bases (lidocaine, (RS)-propranolol and diazepam), with immobilized artificial membrane (lAM)-HPLC, as compared to partitioning in the standardized phosphatidylcholine liposome/buffer system. Methods. The pH-dependent apparent partition coefficients D were calculated from capacity factors (k_IAM) obtained by IAM-HPLC, using a 11-carboxylundecylphosphocholine column. For lipophilic compounds k_IAM, values were determined with organic modifiers and extrapolation to 100% water phase (k_IAMw) was optimized. Temperature dependence was explored (23 to 45° C), and Gibbs free energy (G), partial molar enthalpy (H) and change in entropy (S) were calculated. Equilibrium dialysis was used for the partitioning studies with the liposome/buffer system. Results. For extrapolation of k_IAMw, linear plots were obtained both with the respective dielectric constants and the mole fractions of the organic modifier. All tested compounds showed a similar pH-D diagram in both systems; however, significant differences were reproducibly found in the pH range of 5 to 8. In all cases, G and H were negative, whereas S values were negative for acids and positive for bases. Conclusions. In both partitioning systems, D values decreased significantly with the change from the neutral to the charged ionization state of the solute. The differences found under physiological conditions, i.e. around pH 7.4, were attributed to nonspecific interactions of the drug with the silica surface of the IAM column.