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     

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     

Relaxation of hormonally stimulated smooth muscular tissues by the 8-bromo derivative of cyclic GMP

Summary Substances that cause contraction or relaxation of smooth muscle have been shown to increase intracellular levels of cyclic GMP. Because of the unclear role of cyclic GMP in the control of smooth muscle tone, cyclic GMP derivatives were exogenously applied to various smooth muscle preparations and their effects on tissue tone were studied.Whereas the basal tone of the rat ductus deferens was not affected by exogenous cyclic GMP or its dibutyryl or 8-bromo derivatives, the contractile responses of this tissue to noradrenaline and acetylcholine were depressed by preincubation with 10 M 8-bromo cyclic GMP (Br-cGMP). The 8-bromo derivatives of 2:3-cyclic GMP, 5-GMP and guanosine were without effects. Cyclic AMP levels were not changed by Br-cGMP. The frequency of oxytocin-stimulated rat uteri was also depressed by Br-cGMP (10 M). In helical strips of rat and rabbit aortae, Br-cGMP (1–100 M) caused a concentration-dependent, rapid decrease in noradrenaline-stimulated tissue tension. Br-2:3-cyclic GMP was ineffective. Noradrenaline-stimulated strips from hog spleen arteries were less sensitive to Br-cGMP than aortic tissue. In ductus deferentes and aortic strips stimulated by K⁺ at a depolarizing concentration, Br-cGMP caused less relaxation than under hormonal stimulation.These findings support the concept that cyclic GMP is involved in the control of smooth muscle tone and that hormone- and drug-induced elevations of the cyclic GMP level can reduce contractile responses to neurotransmitters and hormones.Abbreviations cGMP Guanosine 3:5-monophosphate, cyclic GMP - dibutyryl cGMP N², 2-O-dibutyryl guanosine 3:5-monophosphate - Br-cGMP 8-bromo guanosine 3:5-monophosphate - Br-2:3-cGMP 8-bromo guanosine 2:3-monophosphate - Br-GMP 8-bromo guanosine 5-monophosphate - Br-Guo 8-bromo guanosine, Br-guanosine - cAMP adenosine 3:5-monophosphate, cyclic AMP - dibutyryl cAMP N⁶, 2-O-dibutyryl adenosine 3:5-monophosphate - Br-cAMP 8-bromo adenosine 3:5-monophosphate This work was supported by grants from the Deutsche Forschungsgemeinschaft. Preliminary reports were presented (Schultz, 1977b; Schultz et al., 1978).     

The in vitro/in vivo comparative metabolism of 4-aminobiphenyl using isolated hepatocytes

The metabolism of 4-aminobiphenyl by isolated hepatocytes from various species was compared with urinary metabolite profiles in the same species. Radioactive compounds in concentrates of ether extracts from hepatocytes or urine following hydrolysis were analysed by TLC and reversed phase HPLC in conjunction with radioactivity monitoring and synthetic standards.The major metabolites from hepatocytes and in urine were 4-acetamidobiphenyl, 3-hydroxy-4-aminobiphenyl 4-hydroxy-4-aminobiphenyl and 4-hydroxy-4-acetamidobiphenyl. Oxidation of the amine nitrogen gave hydroxylamino, nitroso and nitro compounds. Minor metabolites were 2-hydroxy amine and amide, the hydroxamic acid and the oxamic acid. The urinary metabolite profiles correlated well with those from hepatocytes for each species.Abbreviations Used 4-ABP 4-aminobiphenyl - AA 4-acetamidobiphenyl - A3-OH 3-hydroxy-4-aminobiphenyl - A4-OH 4-hydroxy-4-aminobiphenyl - A2-OH 2-hydroxy-4-aminobiphenyl - AA4-OH 4-hydroxy-4-acetamidobiphenyl - AA3-OH 3-hydroxy-4-acetamidobiphenyl - AA2-OH 2-hydroxy-4-acetamidobiphenyl - AAN-OH N-hydroxy-4-acetamidobiphenyl - NBP 4-nitrobiphenyl - AN-OH 4-hydroxylaminobiphenyl - NOBP 4-nitrosobiphenyl Dedicated to Professor Dr. med. Herbert Remmer on the occasion of his 65th birthday     

Prodrugs of 5-Iodo-2′-Deoxyuridine for Enhanced Ocular Transport

Problems associated with the use of 5-iodo-2-deoxyundine (IDU) in the treatment of herpes simplex keratitis can be attributed largely to the polar nature of IDU resulting in its poor permeability across the lipoidal epithelial layer of the corneal membrane. Five aliphatic 5-esters of IDU were synthesized and evaluated as prodrugs for potential use in the treatment of deep ocular infections such as stromal keratitis, iritis, and even retinitis. A parabolic relationship between in vitro corneal membrane permeability and carbon chain length of prodrugs is evident. For a given prodrug, enzymatic hydrolysis proceeded most readily in iris–ciliary body, followed by cornea and aqueous humor. An increase in carbon chain length made the prodrugs more enzymatically labile but more resistant to chemical hydrolysis at pH 7.4 and 34°C. The 5-butyryl ester of IDU exhibited an approximately fourfold increase in aqueous humor IDU concentration relative to IDU at 25 min following instillation of 25-µl 5 mM solutions.     

Hybrid Pharmacokinetic Models to Describe Anti-HIV Nucleoside Brain Disposition Following Parent and Prodrug Administration in Mice

Brain delivery of active anti-HIV compounds is important for successful treatment of the AIDS patient. As an initial step in predicting human brain drug concentrations, hybrid pharmacokinetic models were developed to characterize the disposition of anti-HIV nucleosides following parent and prodrug administrations in mice. Mouse data were obtained following intravenous administration of 3-azido-2,3-dideoxyuridine (AZddU or AZDU), 3-azido-3-deoxythymidine (AZT), and their dihydropyridine prodrugs (AZddU-DHP and AZT-DHP). Exponential equations were fitted to the serum concentration–time data for each species, including the pyridinium ion moieties, and subsequently used in differential mass balance equations describing the brain dynamics of each compound. Model parameters for the mass balance equations were estimated by various techniques, including the utilization of in vitro data. In general, model-predicted brain concentrations agreed with the observed data. Similar data in larger animals will permit scale-up of the current model to predict human brain drug concentrations.     

Adenosine 3′,5′-monophosphate in cultured neuroblastoma cells: Effect of adenosine,phosphodiesterase inhibitors and benzazepines

Summary The effect of various neurohormones on intracellular levels of adenosine 3,5-monophosphate were evaluated in a neuroblastoma cell line both, in the presence and in the absence of the phosphodiesterase inhibitors isobutylmethylxanthine and papaverine. Without the phosphodiesterase inhibitors only prostaglandin E₁ increased intracellular adenosine 3,5-monophosphate levels. In the presence of isobutylmethylxanthine and/or papaverine, however, adenosine stimulated adenosine 3,5-monophosphate formation and the effect of prostaglandin E₁ was greatly potentiated. Treatment of the cells with dopamine, 5-hydroxytryptamine, noradrenaline, adrenaline, histamine and prostaglandin F₁ was without effect on adenosine 3,5-monophosphate levels either in the presence or absence of the phosphodiesterase inhibitors. The adenosine concentration for a half maximal effect was about 75 M. The effect of 0.1 mM adenosine was not antagonized by 1 mM theophylline. Several adenosine analogs were tested and found to have little or no effect on adenosine 3,5-monophosphate levels in neuroblastoma N4TG3. Diazepam and to a lesser extent chlordiazepoxide act like phosphodiesterase inhibitors when incubated together with prostaglandin E₁.Part of this work was done during a visit of the authors to NIH, U.S.A., J. S. being a fellow of the Deutsche Forschungsgemeinschaft and B. H. of the Max-Planck-Gesellschaft.     

Identification of the Diastereomers of Pentobarbital N-Glucosides Excreted in Human Urine

A study was undertaken to determine if humans excreted pentobarbital N-glucosides as urinary metabolites following oral administration of pentobarbital. (lRS,5RS)-l--D-Glucopyranosyl) pentobarbital ((lRS,5RS)-PTBG) was isolated from the urine of one subject. The two diastereomers, (lRS,5R)-PTBG and (lRS,5S)-PTBG were separated and found to be identical to synthetic standards when compared using HPLC retention times coupled with UV (with and without post-column ionization) and mass spectrometry (HPLC/ MS). A HPLC method was developed for detecting and quantifying (lRS,5R)-PTBG, (lRS,5S)-PTBG and pentobarbital in urine. Following a single oral dose of sodium pentobarbital to male subjects (n = 6), 1.6–6.2% of the pentobarbital dose was excreted as (lRS,5S)-PTBG over 60 hours. (lRS,5R)-PTBG was also detected in one subject and accounted for 0.3% of the pentobarbital dose. Using a modified HPLC system, the four pentobarbital N-glucosides were resolved and analysis of a partially purified pentobarbital N-glucoside extract from one subject indicated that only (lR,5R)-PTBG and (lS,5S)-PTBG could be detected as urinary excretion products. These results indicate that the side chain chirality of pentobarbital may influence the observed enantioselectivity for the formation and/or urinary excretion of the pentobarbital N-glucosides.     

Enhanced Delivery of 5-Iodo-2′-Deoxyuridine to the Brain Parenchyma

5-Ester derivatives of 5-iodo-2-deoxyuridine (IDU) with varying degrees of lipophilicity were examined to evaluate the effectiveness of lipophilic ester prodrugs for enhanced and sustained delivery of IDU to the brain parenchyma. Approximately 1.0% (1.0 ± 0.19; n = 4) of the total radioactivity was found in the brain at 30 min following intravenous administration of the lipophilic benzoyl-5-ester of ¹²⁵I-labeled IDU, whereas IDU per se yielded only 0.01% (0.01 ± 0.06; n = 4). Since the IDU 5-esters generated significantly higher levels of IDU in the brain, an HPLC analysis of IDU in the presence of 5-esters and the metabolite 5-iodouracil was developed to characterize IDU uptake in the brain. The drug was detected at levels of 6.6 and 9.5 µg/g of brain tissue at 3 hr following intravenous administration of valeryl and benzoyl IDU, respectively, at a dose level of 40 mg/kg IDU equivalent each. IDU, on the other hand, when injected at a similar dose level, produced concentration levels below 0.01 µg/g of brain tissue, which was too low to be detected accurately by the HPLC assay. These results suggest that the 5-ester derivatives cross the blood-brain barrier effectively and generate significantly higher brain levels of the parent drug in the brain parenchyma. The regenerated hydrophilic drug because of its polarity is locked in the brain and is subsequently metabolized by pyrimidine phosphorylase to 5-iodouracil. A higher concentration of IDU was generated following administration of the benzoyl ester probably because the ester itself is slowly hydrolyzed by the brain cholinesterases, thereby competitively inhibiting the metabolism of IDU to 5-iodouracil by brain pyrimidine phosphorylase. 5-Benzoyl IDU appears to be a promising bioreversible analogue which can provide enhanced and sustained delivery of IDU to the brain parenchyma.     

Synthesis and Study of 5′-Ester Prodrugs of N6-Cyclopentyladenosine,a Selective A1 Receptor Agonist

Purpose. A series of 5-esters of N⁶-cyclopentyladenosine (CPA) were prepared with the aim to improve stability and bioavailability of selective A₁ agonists. Log P values, stability, affinity, and activity toward human adenosine A₁ receptors were evaluated. Methods. An appropriate synthetic procedure was adopted to avoid concomitant deamination at position 6. Log P values were obtained by the Mixxor system. The stability of CPA and its 5-ester was evaluated in human plasma and whole blood and analyzed with high-performance liquid chromatography. The affinities to human A₁ receptor expressed by N⁶-cyclohexyladenosine cells were obtained by binding experiments. The activities were evaluated by measurements of the inhibition of forskolin stimulated 3-5-cyclic adenosine monophosphate, performing competitive binding assays. Results. All prodrugs were more lipophilic than CPA, and their hydrolysis, in whole blood and in plasma, was found related, respectively, to the length and hindrance of 5-substituents. Affinity and activity values indicated a very weak interaction toward adenosine A₁ receptor of the intact prodrugs. Conclusions. We propose 5-esters of CPA, characterized by suitable lipophilicity and elevated degree of stability in physiological fluids, as possible canditates for CPA prodrugs.     

Nonenzymatic and Enzymatic Hydrolysis of 5-Fluoro-2′-deoxyuridine (FUdR) Esters

The chemical and enzymatic reactivity of 5-fluoro-2-deoxyuridine prodrugs esterified at the 3 and 5 positions with several acyl groups has been investigated. The enzymatic reactivity was affected by the acyl structure, the site of esterification, and the number of esters in the prodrug molecule.     

Cardiostimulatory effects of cyclic 3′,5′-adenosine monophosphate and its acylated derivatives

Summary The effects of cyclic 3,5-AMP and of two acylated derivatives, dibutyryl (DBA) and dihexanoyl-3,5-AMP (DHA) were investigated in isolated perfused hearts of guinea pigs, rats and rabbits.In guinea pig hearts, DBA (Ca- and Na-salt) and DHA-Na in high doses (10 moles) produced strong and long lasting increases in the rate and amplitude of contractions, coronary flow, and moderate increases in phosphorylase activity in the majority of experiments. The positive ino- and chronotropic effects occured 3–5 min after injection of the drug, mostly in a fluctuating manner with several maxima. Theophylline augmented the effects of DBA-Na and revealed positive inotropic actions of non substituted 3,5-AMP.In rat hearts, similar, but more pronounced and dose-dependent effects were observed after 1, 5 and 10 moles DBA-Na. Propranolol (50 g) did not block the action of 10 moles DBA-Na. Non substituted 3,5-AMP, 5-AMP and ATP in doses of 10 moles had no significant positive inotropic effects.In rabbit hearts, DBA-Na (50 moles) produced moderate, non fluctuating rises in the amplitude of contraction.The results provide evidence that under certain conditions cyclic 3, 5-AMP itself, like its acylated derivatives DBA and DHA, may produce strong and direct positive inotropic and chronotropic effects in the heart. These findings support the view that cyclic 3,5-AMP is the cellular mediator of the cardiostimulant actions of substances that increase its rate of production in the myocardial cell.The excellent technical help of Mrs. Vera Bauer is gratefully acknowledged by the authors.     

Hemmung von Adenyl-Cyclase-Präparationen aus der Rattenniere durch Calciumionen und verschiedene Diuretica

Summary Antidiuretic hormone (ADH) increases the permeability to water of certain epithelial membranes. This effect, found in the urinary bladder of the toad and in the distal tubules and the collecting ducts of kidney, is mediated intracellularly by adenosine 35-monophosphate (Ado-35-P). Calcium ions and the diuretic ethacrynic acid are known to inhibit the ADH-induced increase in water permeability of the toad bladder. In adenyl cyclase preparations from rat renal cortex and medulla, the influence of these substances as well as of other diuretics added in vitro has been studied. Adenyl cyclase activity has been determined, excepted as noted, by measuring Ado-35-P formed from 1 mM ¹⁴C-ATP in the presence of 10 mM Mg⁺⁺, an ATP regenerating system, and 5 mM unlabeled Ado-35-P to reduce the enzymatic degradation of the labeled Ado-35-P.Calcium ions reduced the rate of Ado-35-P formation by particles from renal cortex and medulla when the activity was measured in the presence of either Mg⁺⁺ or Mn⁺⁺. With 10 mM Mg⁺⁺, 1 mM Ca⁺⁺ decreased adenyl cylase activity by about 50%. Activities of cortical adenyl cyclase stimulated by parathyroid hormone, thyrocalcitonin or ADH and of medullary adenyl cyclase stimulated by ADH were also reduced by about 50% in the presence of 1 mM Ca⁺⁺. The inhibition was independent of the ATP concentration, but was influenced by the Mg⁺⁺ content of the incubation medium.Adenyl cyclase activities of cortical and medullary membrane preparations were reduced by about 50% by 0.2 mM ethacrynic acid. The extent of this inhibition was essentially the same whether the enzymatic activity was determined in the absence or presence of stimulating hormones. The inhibitory action of ethacrynic acid was partially prevented by simultaneous addition of dithioerythritol (DTE). A derivative of ethacrynic acid, L 589420-0-2, also inhibited renal adenyl cyclase, but its action was not influenced by the addition of DTE. Adenyl cyclase from both parts of the kidney was inhibited by about 90% by 0.2 mM mersalyl. This action was almost completely prevented by the addition of 1 mM DTE. The pharmacological significance of adenyl cyclase inhibition by these diuretics is still uncertain since the role of Ado-35-P in the regulation of sodium transport is as yet unclear.Other diuretics, hydrochlorothiazide, furosemide, mefruside, amiloride, and the non-diuretic benzothiadiazine, diazoxide, had essentially no effect on cortical and medullary adenyl cyclase preparations when they were added in 0.1–0.5 mM concentration.The methylxanthines, theophylline and caffeine, which are known to inhibit nucleoside 35-monophosphate phosphodiesterase, reduced the rate of Ado-35-P formation. The unstimulated and the hormone-stimulated adenyl cyclases were inhibited to the same extent by theophylline. When adenyl cyclases was stimulated by fluoride, however, we found only a very small inhibition by theophylline. Inhibition of the medullary adenyl cyclase was greater than that of the enzyme prepared from renal cortex. At a concentration of 1 mM these methylxanthines significantly inhibited the medullary enzyme, but the inhibition became asymptotic at about 50% when concentrations up to 20 mM were used. Therefore, it is likely that inhibition by these substances varies in different cell types and tissues.Instead of phosphodiesterase inhibitors, unlabeled Ado-35-P can be used in the assay of adenyl cyclase activity to reduce the degradation of enzymatically formed labeled Ado-35-P. This addition, though, can also influence adenyl cyclase activity. In a medullary enzyme preparation 0.2 mM Ado-35-P reduced the adenyl cyclase activity by 13%, 5 mM Ado-35-P by 35%.

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Abkürzungen Ado-35-P Adenosin-35-monophosphat - Guo-35-P Guanosin-35-monophosphat - ADH antidiuretisches Hormon, Vasopressin - PTH Parathormon - TCT Thyreocalcitonin - DTE Dithioerythrit - EDTA Äthylendiamintetraessigsäure Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.Über einen Teil der Ergebnisse wurde auf der 11. Frühjahrstagung der Deutschen Pharmakologischen Gesellschaft berichtet (Jakobs et al., 1970). Einige der vorliegenden Ergebnisse sind der Inauguraldissertation von K. H. J. (Medizinische Fakultät der Universität Heidelberg, 1971) entnommen.     

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.     

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.     

Toxicokinetic interactions between chlorinated aromatic hydrocarbons in the liver of the C57BL/6J mouse: I. Polychlorinated biphenyls (PCBs)

2,2,4,4,5,5- (PCB 153), 2,3,3,4,4,5- (PCB 156) and 3,3,4,4,5,5-hexachlorobiphenyl (PCB 169) were administered orally to three groups of C57BL/6J mice using single doses of 1.5–109.1 mg/kg. Two other groups of mice received binary mixtures of PCB 153 and 156 or PCB 153 and 169. The hepatic deposition, elimination, CYP1a and CYP2b dependent enzyme activities were studied during a 77-day period. Some interactive effects on hepatic deposition and elimination were observed, resulting in increased deposition and faster elimination. These effects were most pronounced for the PCBs 156 and 169. A potentiating effect on hepatic CYP1a dependent 7-ethoxyresorufin-O-deethylation (EROD) activity was observed for the combination of PCB 156 and 153. Based on the results from the present study and earlier studies, it is suggested that the potentiating effect on EROD activity might be caused by a mechanism that is governed by at least two factors. The first is a toxicokinetic modulation of hepatic retention. The second factor is probably an elevation of hepatic Ah receptor levels by PCB 153.     

Effects of N-chlorobenzyl analogues of amiloride on myocardial contractility,Na-Ca-exchange carrier and other cardiac enzymatic activities

Summary 1. In electrically driven guinea pig left atria, micromolar concentrations (2 mol/l to 80 mol/l) of N-chlorobenzyl derivatives of amiloride (o-chlorobenzamil and 3,4-dichlorobenzamil) produced quantitatively similar positive inotropic effects. Contracture developed with 3,4-dichlorobenzamil. Endogenously released catecholamines contributed 30% to the positive inotropic effect of ochlorobenzamil but did not contribute at all to the effect of 3,4-dichlorobenzamil. When tested in the presence of the inhibitor of phosphodiesterase isobutylmethylxanthine, ochlorobenzamil antagonized its positive inotropic effect, whereas 3,4-dichlorobenzamil potentiated it. o-Chlorobenzamil also antagonized the positive inotropic effect of ouabain in that it shifted its concentration-effect curve to the right. Moreover, o-chlorobenzamil prevented the appearance of ouabain toxicity in terms of a rise in the resting force. 2. Also, in electrically driven guinea pig papillary muscle, micromolar concentrations (5 mol/l to 30 mol/l) of both N-chlorobenzyl derivatives of amiloride produced a positive inotropic effect. This effect was more marked with 3,4-dichlorobenzamil than with o-chlorobenzamil and was associated for both compounds with lengthening of relaxation time. 3. o-Chlorobenzamil and 3,4-dichlorobenzamil influenced, though not to the same extent, several systems involved in the onset and in the control of cardiac contractility. 3,4-Dichlorobenzamil inhibited with the same potency Na-K-ATPase, sarcotubular Ca-ATPase, Na-Ca-exchange carrier, cAMP-dependent phosphodiesterase isolated from bovine heart and oxidative phosphorylation of mitochondria isolated from rat liver. Low micromolar concentrations of o-chlorobenzamil mainly inhibited Na-Ca-exchange carrier and cAMP-dependent phosphodiesterase. 4. The results suggest that 3,4-dichlorobenzamil is a quite unspecific compound and its cardiac effects are the result of an interference with several enzymatic and transport systems. In contrast, both the inhibition of the Na-Ca-exchange carrier and cAMP-dependent phosphodiesterase can contribute to the increase in the force of contraction induced by o-chlorobenzamil. Finally, the antagonism of o-chlorobenzamil against the cardiac effects of ouabain can be explained by the inhibition of the Na-Ca-exchange carrier. Send offprint requests to M. Floreani     

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.     

Dehydro-digitoxosides of digitoxigenin and digoxigenin: Binding to beef heart (Na++K+)-ATPase in relation to unchanged digitoxosides

Summary Dehydro-digitoxosides are metabolites of digitalis glycosides. In order to study their possible biological activity their affinity to (Na⁺+K⁺)-activated ATPase was determined and compared with unchanged glycosides. Based on the dissociation constants of glycoside-enzyme-complexes, the affinity of the dehydro-digitoxosides ranged in the same order of magnitude as that of the native glycosides. Comparing mono-, bis-, and tris-digitoxosides of digitoxigenin (dt-1, dt-2, dt-3) and of digoxin (dg-1, dg-2, dg-3) with the corresponding dehydrodigitoxosides (3-dehydro-dt-1, 9-dehydro-dt-2, 15-dehydro-dt-3, 3-dehydro-dg-1 and 9-dehydro-dg-2, respectively) the dehydro-digitoxosides had lower affinities to the enzyme. The highest dissociation constants (K _D)were found for 3-dehydro-dt-1 and 3-dehydro-dg-1. The half maximal inhibition of (Na⁺+K⁺)-ATPase activity (I₅₀) corresponded to affinity measurements in all but two cases: dehydro-dt-3 and dehydro-dt-2 showed very low I₅₀ values.     

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.