Mechanism of alkylation by N-nitroso compounds: detection of rearranged alcohol in the microsomal metabolism of N-nitrosodi-n-propylamine and base-catalyzed decomposition of N-n-propyl-N-nitrosourea

Metabolism of N-nitrosodi-n-propylamine by an isolated rat liver microsomal fraction yielded 17% isopropanol and 83% n-propanol (expressed as a percentage of total propanol formed). Base-catalyzed decomposition of N-n-propyl-N-nitrosourea yielded 39% isopropanol and 61% n-propanol. The values provide evidence for involvement of carbocations in both of these reactions.

N-nitroso-bis(2-acetoxypropyl)amine as a further pancreatic carcinogen in Syrian golden hamsters

N-Nitroso-bis(2-acetoxypropyl)amine, a possible beta metabolite of N-nitroso-di-n-propylamine, was shown to be a potent carcinogen in the Syrian golden hamster. After a single s.c. treatment, the pancreas was the most affected organ, followed by the liver, respiratory tract, and kidneys. However, repeated application resulted in a higher incidence of neoplasms of the respiratory tract than of the pancreas and kidneys. The effect of N-nitroso-bis(2-acetoxypropyl)amine on toxicity, target tissues, and carcinogenicity was similar to that of N-nitroso-bis(2-hydroxypropyl)amine. The assumption that these two compounds may have similar metabolic pathways was confirmed; N-nitroso-bis(2-acetoxypropyl)amine was readily deesterified to N-nitroso-bis(2-hydroxypropyl)amine in vivo and in vitro.

A further pancreatic carcinogen in Syrian golden hamsters: N-nitroso-bis(2-acetoxypropyl)amine

Weekly subcutaneous injection of N-nitroso-bis(2-acetoxypropyl)amine (BAP) for 20 weeks to Syrian golden hamsters induced pancreatic neoplasms in 50% of the animals, as early as 15 weeks from the start of treatment. The carcinogenic potency and organotropic spectrum of BAP were similar to those of N-nitroso-bis(2-hydroxypropyl)amine (BHP). Metabolism studies indicated that BAP was readily converted in vivo to BHP and that BHP was also the major urinary metabolite.

Metabolism of n-propylamine, isopropylamine, and 1,3-propane diamine by Mycobacterium convolutum

Mycobacterium convolutum strain NPA-1 can utilize n-propylamine (NPA), isopropylamine (IPA), and 1,3-propane diamine (PD) as sole source of carbon, nitrogen, and energy. Enzyme assays, fatty acid profiles, and 14CO2 incorporation experiments indicate that NPA is deaminated to propionate and further metabolized via the methylmalonyl succinate pathway, and IPA and PD were metabolized (after deamination) through a C2 + C1 cleavage. An inducible amine dehydrogenase was present in cell extracts after growth on the three amines. Polyacrylamide gel electrophoresis of cell extracts from NPA- and IPA-grown cells yielded one major band of amine dehydrogenase activity. When extracts of NPA-grown cells were assayed with NPA, IPA, or PD as substrate, the relative position of the major band on gel electrophoresis was equivalent. Similar results were obtained with extracts prepared from IPA-grown cells. Sephadex G-100 chromatography also indicated one major peak of activity. This suggests that one enzyme of broad specificity is involved in deamination of IPA, NPA, and PD. IPA-grown cells utilized NPA readily, whereas NPA-grown cells could not utilize IPA without lag. Since amine dehydrogenase activity was present in extracts of cells after growth on either substrate, this lag was probably due to the inability to transport IPA without an induction period. The molecular weight of the amine dehydrogenase was approximately 38,500 as determined by gel filtration.

[Stability of amphetaminil. 2. In vivo studies]

The metabolism of radioactively labelled alpha-phenyl-alpha-N-(beta-phenyl-isopropyl)-aminoacetonitrile (amphetaminil, AN 1-R) (tritium-labelled in the amphetamine-part, 14C-labelled in the benzaldehyde-part of the molecule) in the rat was examined. In the body amphetaminil is cleft very quickly into the original compounds of its chemical synthesis (amphetamine, benzaldehyde and hydrocyanic acid) independent of the mode of application (i.p. or oral). Blood: In the interval from 5-90 min after application of amphetaminil only 1-2 percent of the total radioactivity are received from amphetaminil. The main part of the tritium- and 14C-radioactivity is distributed among amphetamine, p-OH-amphetamineglucuronide and hippuric acid. Brain: In the brain only a minimum amount of amphetaminil can be present, if any. The share of amphetamine of the total activity amounts to more than 90 percent. Adipose tissue: In the adipose tissue the ratio of the two isotopes of the substances extracted at pH 5 is almost equal to that of the administered amphetaminil. It seems that the substance is enriched there because of its pronounced lipophilia. After i.p. application the concentration is about 12 times higher than after oral application. Urine: In the urine there could be detected amphetamine, p-OH-amphetamineglucuronide and hippuric acid but no amphetaminil.

A review of the metabolism of amide local anaesthetic agents

(1) Amide local anaesthetics are almost completely metabolized before excretion in both animals and man. (2) Considerable interspecies variability occurs in the quantitative excretion of local anaesthetic metabolites; however, qualitative similarities often exist. (3) The secondary amine metabolite of lignocaine, MEGX, is capable of reacting in vivo with acetaldehyde, formed as a metabolite of ethyl alcohol, to produce a cyclic condensation product. (4) Although hydrolysis in man of the secondary amine metabolite of lignocaine, MEGX, appears extensive, the same is not true for the metabolic analogue produced from mepivacaine, PPX. (5) Metabolism of mepivacaine by the neonate is impaired, but the excretion process in the newborn is capable of eliminating the drug within 24 hr after birth. (6) Metabolic data on bupivacaine and etidocaine are incomplete. The latter compound appears to have a more rapid plasma clearance.

Pharmacology of local anaesthetic agents. Pharmacokinetics of local anaesthetic agents

Information derived from measurements of blood concentrations of local anaesthetics can be extended by the application of pharmacokinetic anaylsis. A better understanding of quantitative aspects of the disposition and absorption of these drugs should assist the anaesthetist in deciding the optimal agent and dosage for regional block techniques.

Kinetics of three structurally related bicyclic antidepressant compounds--a comparison in the dog

Kinetic experiments have been made with three structurally related compounds selected from a series of bicyclic antidepressant compounds. Plasma concentrations were assayed after doses of 5 mg kg−1 given as an intravenous infusion over 2 h to three dogs. The data were evaluated according to a two compartment open model, and kinetic parameters reflecting distribution and elimination characteristics of the drugs were calculated. An attempt was made to evaluate possible relations between chemical structure and these parameters. The lowest drug levels and the most rapid elimination were obtained with a compound utilizing sulphoxidation as an additional pathway of metabolism. The compounds lacking this possibility had considerably slower elimination kinetics, the less lipophilic being the slowest one. Little individual variation was seen. A relation between increased lipophilicity and increased localization in the peripheral compartment was indicated. However, the importance of other factors, such as binding phenomena within tissues, was also indicated.