Characterization of benzazepine UDP-glucuronosyl-transferases in laboratory animals and man

Bis(hydroxyphenyl)methane-bisphenol F-metabolism by the HepG2 human hepatoma cell line and cryopreserved human hepatocytes

Bisphenol F (BPF) is present in the environment and as a contaminant of food. Humans may, therefore, be exposed to BPF, and an assessment of this risk is required. BPF has been shown to have genotoxic and endocrine-disruptor properties in a human hepatoma cell line (HepG2), which is a model system for studies of xenobiotic toxicity. In this study, we investigated the ability of HepG2 cells to biotransform BPF, because metabolism may affect the observed effects of BPF, and we compared this metabolic capacity with that of human hepatocytes. Cells were incubated for 24 hours with [(3)H]-BPF. The culture medium was then concentrated and its metabolites were isolated by high-performance liquid chromatography and identified by mass spectrometry. BPF was largely metabolized into the corresponding sulfate by the HepG2 cell line. BPF was metabolized into both sulfate and glucuronide by human hepatocytes, but with differences between individuals. The metabolism of BPF in both HepG2 cells and human hepatocytes suggests the existence of a detoxification pathway. Thus, these two cell models differ in metabolic capacity. It is, therefore, very important, when assessing the toxic effects of substances in vitro, to determine, in parallel, the biotransformation capacities of the model used to extrapolate in vivo.

Normal-phase liquid chromatography-particle-beam mass spectrometry in drug metabolism studies of the dopamine receptor antagonist Odapipam and the muscarine M1 receptor agonist Xanomeline

1. The metabolism of Odapipam has been studied with phenobarbital-induced rat liver microsomes, followed by analysis with normal-phase hplc in combination with particle-beam mass spectrometry. 2. During the incubation of Odapipam, five different metabolites were formed. The EI+ mass spectra of the metabolites indicated the formation of N-desmethyl-Odapipam, 1-hydroxy-Odapipam, the two isomers of 3'-hydroxy-Odapipam and a metabolite which was dehydrogenated in the dihydrobenzofuran moiety. 3. The intrinsic hepatic extraction ratio and metabolism of Xanomeline has been studied in the perfused rat liver. Increasing the input concentration resulted in measurable concentrations of Xanomeline in the perfusate, although the extraction ratio was still > 0.9 at 140 microM. 4. Analysis of the perfusate by normal-phase hplc and particle-beam mass spectrometry showed the formation of at least six metabolites. The EI+ mass spectrum of the metabolites indicated the formation of omega-3 hydroxy-, omega-2 hydroxy-, omega-1 hydroxy-, omega-1 keto-Xanomeline in addition to omega-1 hydroxy-N-desmethyl-Xanomeline and an N-oxide of Xanomeline. 5. The results show that normal-phase hplc based on silica material is superior to reversed-phase-based systems in terms of selectivity. Furthermore, the use of non-aqueous solvents in combination with particle-beam mass spectrometry is advantageous compared with reversed-phase hplc since changing between different solvents in normal-phase hplc results only in minor changes in the particle-beam interface parameters such as nebulizer position, helium pressure and interface temperature.

11C- and 76Br-labelled NNC 22-0010, selective dopamine D1 receptor radioligands for PET

NNC 22-0010 is a new dopamine antagonist with a high affinity and selectivity for D1 receptors in vitro. NNC 22-0010 has both an N-methyl group and a bromine, which allows radiolabelling with either 11C or 76Br. We labelled [11C]NNC 22-0010 by N-methylation of the free base of the secondary amine with [11C]methyl iodide in a total radiochemical yield of 40%. The total synthesis time was 30 min. The specific radioactivity at time of injection of the radioligand was 48 to 55 GBq/mumol. The [76Br]NNC 22-0010 was synthesized from the iodine precursor by an exchange reaction with 76Br using a Cu(+)-assisted nucleophilic substitution reaction. The radiochemical yield was 60% after purification. Specific radioactivity at time of injection of the radioligand was 6 to 20 GBq/mumol. In PET experiments with [11C]NNC 22-0010 and [76Br]NNC 22-0010 there was a rapid uptake of radioactivity in the monkey brain. The striatum-to-cerebellum ratio was 2-2.5 after 1 h. Binding in the striatum was displaced by SCH 23390, whereas binding in the cerebellum was not reduced. Metabolite studies showed that 1 h after injection about 20% of the radioactivity in plasma represented unchanged radioligand. This value was on the same level for at least 6 h. The results indicate that radiolabelled NNC 22-0010 has potential for imaging dopamine D1 receptors selectively in the human brain.