In vitro characteristics of guinea pig lung aromatic azaheterocycle N-methyltransferase.

The in vitro characteristics of guinea pig lung aromatic azaheterocycle N-methyltransferase have been determined, using R-(+)-nicotine as substrate. The enzyme is a cytosolic, S-adenosyl-L-methionine-dependent N-methyltransferase exhibiting apparent KM values of 14.2 and 13.

Effect of nicotine and N'-nitrosonornicotine on rat lung and trachea ornithine decarboxylase activity.

The exposure of rats to tobacco smoke was previously reported to cause an increase in lung and trachea ornithine decarboxylase (ODC) activity. In the present paper we test the effects of the tobacco-specific components nicotine and N'-nitrosonornicotine (NNN) on lung and trachea ODC activity. In addition, a procedure for the synthesis of analytically pure NNN is described.

High-performance liquid chromatographic analysis of pulmonary metabolites of Leu- and Met-enkephalins in isolated perfused rat lung.

A high-performance liquid radiochromatographic analytical system has been developed which allows the determination of [3H]Leuenkephalin, [3H]Met-enkephalin and their potential metabolites [3H]TyrGlyGlyPhe, [3H]TyrGlyGly, [3H]TyrGly and [3H]tyrosine. Using this procedure, the biotransformation of each of the above enkephalins after 20 min of recirculating transit through isolated perfused rat lungs resulted in the formation of two major metabolites: tyrosine and TyrGlyGly in each case. The results indicate that significant metabolism of enkephalins may occur in the pulmonary circulation.

Biotransformation of primary nicotine metabolites. I. In vivo metabolism of R-(+)-[14C-NCH3]N-methylnicotinium ion in the guinea pig.

The in vivo biotransformation and tissue distribution of the methylated nicotine metabolite R-(+)-[14C-NCH3]N-methylnicotinium acetate was studied in the guinea pig. The detection and quantification of 24-hr urinary metabolites after ip injection was determined by cation-exchange HPLC interfaced to a radiochemical flowthrough detector. The urinary metabolite profile consisted of five peaks.

Synthesis and pharmacological evaluation of aromatic dihydroxylated spiro[indan-1,3'-pyrrolidine] and spiro[indan-2,2'-pyrrolidine] derivatives.

Aromatic hydroxylated derivatives of the spiro[indan-1,3'-pyrrolidine] and spiro[indan-2,2'-pyrrolidine] ring systems have been synthesized and evaluated for dopaminergic agonist and antagonist activities. None of these conformationally restricted catecholamines possessed any dopaminergic activity, but 5,6-dihydroxy spiro[indan-1,3'-pyrrolidine] hydrobromide exhibited weak dopamine antagonist properties.

N-Methylnornicotinium ion, a new in vivo metabolite of R-(+)-nicotine.

N-Methylnornicotinium ion has been identified as a metabolite in the urine of male Hartley guinea pigs that had been chronically dosed ip with R-(+)-nicotine. Under similar conditions, S-(-)-nicotine is not biotransformed into this metabolite. The metabolite was isolated and purified by preparative high performance cation-exchange liquid chromatography.

Remarkable substrate-inhibitor properties of nicotine enantiomers towards a guinea pig lung aromatic azaheterocycle N-methyltransferase.

The kinetics of nicotine methylation by guinea pig lung homogenates has been investigated. An interesting stereospecificity has been observed for nicotine enantiomers. R-(+)-Nicotine is a substrate Km = 1.

Pulmonary metabolism of exogenous enkephalins in isolated perfused rat lungs.

Metabolism of enkephalins during transit through the pulmonary circulation may be of significance in regulating systemic levels of these opioids. To determine whether Leu- and Met-enkephalin are metabolized by the pulmonary circulation, [3H]Tyr-Leu-enkephalin (10 microM) or [3H]Tyr-Met-enkephalin (10 microM) were each administered to isolated rat lungs perfused in a recirculating manner with a physiologic salt solution and a recently developed high-performance liquid radiochromatographic analytical method was used to identify and quantitate metabolites in the perfusion medium. Both Leu- and Met-enkephalin were metabolized in a curvilinear, time-dependent manner.

Stereospecific in vivo N-methylation of nicotine in the guinea pig.

R-(+)-[3H-N'-CH3]N-methylnicotinium ion has been identified as a urinary metabolite of ip administered R-(+)-[3H-N'-CH3]nicotine in the guinea pig. Under similar conditions, S-(-)-[3H-N'-CH3]nicotine is not converted to the corresponding N-methylated metabolite. R-(+)-N-methylnicotinium salt was isolated from the urine of guinea pigs that had been chronically dosed ip with R-(+)-nicotine.

Management of bone disease in the dialysis patient.

Bone disease arises in dialysis patients from either secondary hyperparathyroidism or aluminum accumulation. Certain clinical features and biochemical characteristics may help distinguish these disorders, although a bone biopsy is required for a definitive diagnosis. Hyperparathyroidism is managed by correcting serum phosphorus (dietary phosphate restriction plus phosphate binding agents), raising serum calcium (appropriate dialysate Ca, oral Ca supplements, and vitamin D sterols), and by the direct effect of vitamin D on the parathyroid glands.

Evidence of stereospecificity in the in vivo methylation of [14C](+/-)-nicotine in the guinea pig.

In vivo metabolism of [14C]nicotine to N-methylnicotinium ion in the guinea pig appears to be a stereospecific biotransformation, involving only the R-(+)-isomer. The detection and quantitation of urinary radiolabeled nicotine metabolites after ip injection of either [N-14CH3](+/-)-nicotine or [2'-14C](+/-)-nicotine, was carried out on an HPLC cation-exchange analytical system. Utilizing the recently discovered phenomenon of differential enantiomeric association, the stereo-chemistry of the methylation pathway was determined.

Leucine enkephalin analogues containing a conformationally restrained N-terminal amino acid residue.

Three analogues of leucine enkephalin, in which the terminal tyrosine-1 residue has been replaced by conformationally restrained aromatic amino acids, have been synthesized by classical solution methods. Their opiate agonist potencies on electrically stimulated guinea pig ileum and mouse vas deferens preparations were determined and compared with morphine, Met enkephalin, and Leu enkephalin. None of these analogues had analgesic properties when evaluated on the above tissue preparations or when evaluated by the hot-plate test in mice after subcutaneous and intracerebroventricular administration.

Leu-enkephalin provokes naloxone-insensitive pulmonary vasoconstriction.

Leu-enkephalin evoked dose-dependent pulmonary vasoconstriction in isolated perfused rat lungs. The pressor responses were not attenuated by either naloxone or naltrexone nor were they mimicked by morphine. Blockade of histamine receptors with pyrilamine or blockade of serotonin receptors with methysergide also failed to antagonize leu-enkephalin-induced pulmonary vasoconstrictor responses.

High-performance liquid chromatographic method for the determination of N-methylated metabolites of nicotine.

An analytical method has been developed, using cation-exchange high-performance liquid chromatography, for the analysis of N-methylated metabolites of nicotine. This method has been used to detect and quantitate seven potential in vivo urinary metabolites of [2'-14C]-nicotine, including four methylated nicotine derivatives, in the guinea pig.

Inhibition of bacterial DNA cytosine-5-methyltransferase by S-adenosyl-L-homocysteine and some related compounds.

S-Adenosyl-L-homocysteine and five related compounds have been evaluated as inhibitors of a DNA cytosine-5-methyltransferase. DNA methylation was assayed in cell extracts from E. coli strain J6-2 dcm+, proficient in DNA cytosine-5-methyltransferase activity, containing substrate DNA isolated from E.

Multisubstrate adducts as potential inhibitors of S-adenosylmethionine dependent methylases: inhibition of indole N-methyltransferase by (5'-deoxyadenosyl)[3-(3-indolyl)prop-1-yl]methylsulfonium and (5'-deoxyadenosyl)[4-(3-indolyl)but-1-yl]methylsulfonium salts.

Multisubstrate adducts of the indole N-methyltransferase reaction have been designed in which a structural moiety representing the nucleophilic methyl acceptor is attached through the sulfur atom to the 5-(methylthio)adenosine and/or methionine moieties of the methyl donor, S-adenosyl-L-methionine. Indole derivatives attached through a 4-(3-indolyl)butyl sulfide or a 3-(3-indolyl)propyl sulfide linkage to 5'-thioadenosine or homocysteine have been synthesized, together with their corresponding methylsulfonium salts. These compounds have been assayed for their ability to inhibit rabbit lung indole N-methyltransferase.

Synthesis and analgesic properties of two leucine-enkephalin analogues containing a conformationally restrained N-terminal tyrosine residue.

Two analogues of Leu-enkephalin, in which the terminal tyrosine-1 residue has been replaced by a conformationally restrained tyrosine analogue, have been synthesized by classical solution methods, and their opiate agonist potencies on electrically stimulated guinea pig ileum and mouse vas deferens preparations were determined in comparison with Leu-enkephalin. The restriction in the degree of freedom of the tyrosine moiety in [(2-amino-6-hydroxy-2-tetralinyl)carbonyl]glycylglycylphenylalanylleucine methyl ester (3e) leads to a 7 to 8 times higher agonist activity at the mu-receptor subtype in guinea pig ileum when compared to Leu-enkephalin, and an almost 30-fold decrease in potency, vs. Leu-enkephalin, on mouse vas deferens preparation.

alpha 2-Adrenoceptor agonist properties of exo- and endo-isomers of 2-amino-6,7,dihydroxybenzonorbornene designed as rigid catecholamines.

A series of N-substituted exo- and endo-isomers of 2-amino-6,7-dihydroxybenzonorbornene, designed as rigid catecholamines, have been studied in the pithed rat in-vivo, as vasoconstrictor agents, and as inhibitors of the twitch response in the transmurally stimulated guinea-pig ileum. The exo-isomers examined were vasoconstrictor agonists in the pithed rat and inhibited the twitch response of the ileum. The corresponding endo-isomers were inactive in both preparations.

Microscopy of the dentine of enamel-free areas of rat molar teeth.

Dentine of the enamel-free areas (EFA) of first mandibular molar teeth of rats aged between 20-150 days was examined by scanning electron microscopy. Demineralized sections were stained with Gram-Twort's stain and examined for dental caries. In newly erupted teeth, a few dentinal tubules opened on the EFA surface.

Species differences in the metabolic C- and N-oxidation , and N-methylation of [14C]pyridine in vivo.

1. The metabolism of [2,6-14C]pyridine in vivo has been investigated in the rat, hamster, mouse, gerbil, rabbit, guinea-pig, cat and man, and the quantitative determination of the various urinary metabolites carried out by radiochromatographic analysis. 2.

Synthesis and dopaminergic properties of some exo- and endo-2-aminobenzonorbornenes designed as rigid analogue of dopamine.

Stereospecific syntheses of exo-2-amino-5,6-dihydroxybenzonorbornene (11f), exo-2-amino-6,7-dihydroxybenzonorbornene (11h), exo-2-amino-7,8-dihydroxybenzonorbornene (11g), and endo-2-amino-6,7-dihydroxybenzonorbornene (14d), rigid analogues of dopamine, are described. Compounds 11 h and 14d, their N-methyl (11i and 11j) and N,N-dimethyl (14i and 14j) derivatives, and compounds 11f and 11g were inactive as dopamine agonists when evaluated for dopaminergic activity by their ability to induce stereotyped behavior in mice after subcutaneous injection and by their ability to cause hyperactivity in rats after bilateral injection into the nucleus accumbens. However, compounds 11f, 11g, 11h, and the N-methyl derivatives 11i and 14d were all effective in displacing [3H]-2-amino-6,7-dihydroxytetralin ([3H]ADTN) and [3h[-N-n-propylnorapomorphine ([3H]NPA) from rat striatal membranes.