QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) All Versions of this Article: dmd.105.003764v1 33/11/1708    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Monostory, K. Articles by Kóbori, L. Search for Related Content PubMed PubMed Citation Articles by Monostory, K. Articles by Kóbori, L.

BIOTRANSFORMATION OF DERAMCICLANE IN PRIMARY HEPATOCYTES OF RAT, MOUSE, RABBIT, DOG, AND HUMAN

Katalin Monostory, Krisztina Khalmy, Krisztina Ludányi, Gábor Czira, Sándor Holly, László Vereczkey, Iván Ürmös, Imre Klebovich, and László Kóbori

Chemical Research Center, Hungarian Academy of Sciences, Budapest, Hungary (K.M., K.K., K.L., G.C., S.H., L.V.); EGIS Pharmaceuticals Ltd., Budapest, Hungary (I.Ü., I.K); and Transplantation and Surgery Clinic, Semmelweis University, Budapest, Hungary (L.K.)

(Received January 19, 2005; accepted August 22, 2005)

	Abstract

Top Abstract Materials and Methods Results Discussion References

 
The metabolic fate of deramciclane [(1R,2S,4R)-(–)-2-phenyl-2-(2'-dimethylamino-ethoxy)-1,7,7-trimethyl-bicyclo[2.2.1]heptane], a new anxiolytic drug candidate, has been determined in rat, mouse, rabbit, dog, and human hepatocytes. Rat and rabbit cells were the most active, whereas the rate of metabolism was quite slow in human hepatocytes. During biotransformation, deramciclane underwent side chain modification and oxidation at several positions of the molecule. The side chain modification led to the formation of N-desmethyl deramciclane and phenylborneol. The oxidation of deramciclane resulted in several hydroxy-, carboxy-, and N-oxide derivatives. The hydroxylation took place at primary or secondary carbons of the camphor ring as well as at the side chain; furthermore, dihydroxylated derivatives were also found. The side chain-modified metabolites were also oxidized to hydroxy- or carboxy-derivatives. Conjugation of phase I metabolites, as a route of elimination, was also observed in rat, rabbit, and dog hepatocytes. Although there were some species differences in biotransformation of deramciclane, it was concluded that phase I metabolism in human liver cells seemed to be similar to the metabolism in the hepatocytes isolated from rat. With careful approach, the rat model may be considered to be predictive for human metabolism of deramciclane.

In the last few years, efforts have been made to develop new non-benzodiazepine-type anxiolytics with minimal risk of sedative and muscle relaxant side effects in the therapeutic dose range. Deramciclane, developed by EGIS Pharmaceuticals Ltd. (Budapest, Hungary), is a novel potential anxiolytic agent that is more effective than diazepam or chlordiazepoxide (Gacsályi et al., 1988; Berényi et al., 1990). Deramciclane has been shown to be a potent and relatively specific 5-HT2A/2C receptor antagonist in receptor binding and functional studies (Palvimaki et al., 1998). Its anticonvulsant activity is exerted via inhibition of synaptosomal -aminobutyric acid uptake (Kovács et al., 1989). Our work demonstrates the similarities and differences in biotransformation of deramciclane by comparing catalytic activities of rat, mouse, rabbit, dog, and human hepatocytes.

	Materials and Methods

Top Abstract Materials and Methods Results Discussion References

 
Chemicals. Deramciclane and the putative metabolites, N-desmethyl-deramciclane, 9-hydroxy-deramciclane, deramciclane N-oxide, N-desmethyl 9-hydroxy-deramciclane, phenylborneol, phenylbornylene, phenylcamphene, and 4''-hydroxy-deramciclane were provided by EGIS Pharmaceuticals Ltd. (Budapest, Hungary). [¹⁴C]Deramciclane labeled on the phenyl-ring (1.3394 GBq/mmol) was synthesized at the Chemical Research Center of the Hungarian Academy of Sciences (Budapest, Hungary). Collagenase, HEPES, and Williams' medium E were the products of Sigma Chemie GmbH (Deisenhofen, Germany). All other chemicals for hepatocyte isolation, ß-glucuronidase/arylsulfatase, and ethyl acetate were purchased from Merck (Darmstadt, Germany). Triethylamine was obtained from Loba Feinchemie (Fischamend, Austria). Methanol, dichloromethane, butanol, n-hexane, and chloroform were obtained from ChemoLab (Budapest, Hungary) as chromatography-grade products. All other chemicals were obtained from Reanal (Budapest, Hungary).

Isolation and Culture of Hepatocytes. Experiments were carried out by using hepatocytes prepared from male Wistar rats (240–250 g), NMRI mice (30–35 g) (ToxiCoop Safety Toxicological Study Center, Budapest, Hungary), New Zealand rabbits (3.8–4.3 kg), and beagle dogs (9.5–11.0 kg) (Institute for Drug Research Ltd., Budapest, Hungary). Human livers were obtained from kidney transplant donors at the Transplantation and Surgery Clinic, Semmelweis University (Budapest, Hungary). Permission of the Local Research Ethics Committee was obtained to use human tissues. The liver cells were isolated by the method of Bayliss and Skett (1996). Hepatocytes having viability better than 90%, as determined by trypan blue exclusion (Berry et al., 1991), were used in the experiments. The cells were plated at a density of 4 x 10⁶ cells/dish onto 60-mm plastic dishes precoated with collagen in medium described by Ferrini et al. (1998).

Biotransformation of Deramciclane. Hepatocytes were maintained in primary culture for 24 h in culture medium containing 50 µM deramciclane (266.4 MBq/mmol). After the incubation period, the cells and extracellular medium were separated and the metabolites were extracted with dichloromethane. Conjugates of deramciclane metabolites formed in hepatocytes were subjected to enzymic hydrolysis by ß-glucuronidase/arylsulfatase in 0.1 M sodium acetate buffer (pH 4.4), and then the metabolites were extracted with dichloromethane. The organic phases were evaporated to dryness in vacuo and the residue was resolved in methanol. The radioactivity of the samples at each stage was followed by liquid scintillation techniques (LKB 1217 Rackbeta type; Amersham Biosciences, Uppsala, Sweden). Radioactivity recoveries for the extractions ranged from 89% to 99%. The extracts of the cells or the extracellular medium (before and after enzymic hydrolysis) were analyzed by thin-layer chromatography on 0.2-mm-thick DC-Alufolien Kieselgel 60 F₂₅₄ plates (Merck) using three different delivery systems: 1) ethyl acetate/triethylamine (25:1 v/v), 2) butanol/acetic acid/water (4:1:1 v/v), and 3) n-hexane/chloroform (1:1 v/v). The amounts of deramciclane and its metabolites were calculated on the basis of digital autoradiography by a Berthold digital autoradiograph type LB-287 (EG&G; Berthold Technologies, Bad Wildbad, Germany). The metabolites were identified on the basis of R_f values on thin layer compared with the authentic standards, or on the basis of mass spectrometric and infrared spectroscopic analyses. The spots containing the metabolites were directly transferred to the mass spectrometer (Ludányi et al., 1997) or they were eluted from thin-layer plates with methanol; the samples were evaporated and subjected to spectroscopic analysis.

Mass Spectrometric Analysis. Attempts were made to identify the chemical structures of separated and eluted metabolites by mass spectrometric analysis using a reverse geometry VG-ZAB-2SEQ type mass spectrometer (Waters, Manchester, UK). Cs⁺ ions (30 kV) were used in fast-atom bombardment (FAB) ionization mode and the matrix was glycerol. Tandem mass spectra were observed by the mass-analyzed ion kinetic energy spectrometry technique combined with collision-induced decomposition (CID) using argon collision gas at a pressure corresponding to 50% main beam transmission. The resolution of exact mass measurements was 10,000. Some samples separated by thin-layer chromatography were further analyzed by gas chromatography/mass spectrometry (GC-MS) with the following GC-experimental conditions: HP-5890 GC instrument equipped with a capillary column (25 m x 0.25 mm x 0.25 µm Cp-Sil 8), helium carrier gas (2 ml/min). In these experiments, electron impact ionization was performed at 70 eV electron energy and at 200°C source temperature.

Infrared Spectroscopic Analysis. For the on-line GC-infrared investigations of the metabolites, a NICOLET 170 SX Fourier-transform spectrometer connected to a Varian 3700 type gas chromatograph was used. The experimental parameters were as follows: Ge/KBr beamsplitter, quartz light-pipe (150 mm x 0.5 mm), helium carrier gas (6 ml/min), HP-1 column (10 m, 0.53 mm).

	Results

Top Abstract Materials and Methods Results Discussion References

 
Biotransformation of Deramciclane. In vitro metabolism of deramciclane was studied in primary hepatocytes isolated from rat, mouse, rabbit, dog, and human. The metabolites formed during the 24-h incubation period were extracted from the cells or from the extracellular matrix and analyzed by thin-layer chromatography and autoradiography. Table 1 summarizes the amounts of deramciclane and its metabolites with their structures, chromatographic properties, mass spectrometric data (molecular ion and fragment ions), and the species that were able to produce the given metabolites from deramciclane.

The most extensive metabolism of deramciclane was observed in liver cells of rat and rabbit. After the 24-h incubation period, deramciclane could be detected merely in trace (less than 10% of deramciclane amount present at 0 min) in the cells or in the extracellular medium. The rate of biotransformation was much slower in mouse and dog hepatocytes; about 40% and 50% of the deramciclane amount remained unchanged. Human liver cells were much less active than the hepatocytes from any animal species investigated.

Figure 1 displays the metabolic profile found in extracts of rat hepatocytes and extracellular medium. Metabolites were separated on thin-layer plates with an ethyl acetate/triethylamine (25:1 v/v) delivery system and were detected by digital autoradiography. Although the metabolites were identified on the basis of R_f values compared with the authentic standards, the final evidence for the structures was provided by mass spectrometric analysis. Demethylation of deramciclane resulted in the formation of N-desmethyl deramciclane (M4), which was found mainly inside the cells because of its lipophilicity. The main metabolite produced by rat liver cells was 9-hydroxyderamciclane (M5), which was eliminated primarily as glucuronide. Other hydroxylated metabolites, hydroxy-deramciclane II (M6, hydroxy-group was located at the 5- or 6-position of the camphor ring), N-desmethyl 9-hydroxy-deramciclane (M2), and N-desmethyl hydroxy-deramciclane II (M3), were also detected as minor metabolites as well as phenylborneol and its hydroxylated derivatives (M8).

View larger version (33K): [in this window] [in a new window]   FIG. 1. Deramciclane metabolites produced by rat hepatocytes. After a 24-h incubation period, the extracts of the cells (a) and extracellular matrix (b) were analyzed by thin-layer chromatography with the mobile phase of ethyl acetate/triethylamine (25:1 v/v).

The metabolic profile found in human cells lacked some of the deramciclane derivatives that were detected in hepatocytes of other species. On the other hand, none of the metabolites could be considered as the major one; all of them were produced at a similar rate. Hydroxylation and side chain modification resulted in hydroxyderamciclane II (M6), N-desmethyl deramciclane (M4), and phenylborneol (M8). 9-Hydroxy-deramciclane (M5) and N-desmethyl 9-hydroxy-deramciclane (M2) were not produced in detectable amounts, whereas N-desmethyl hydroxy-deramciclane II (M3) was detected in trace in the extracts of extracellular liquid. Conjugation of phase I metabolites was not observed at all.

View larger version (33K): [in this window] [in a new window]   FIG. 2. Mass spectrometric behavior of 9-hydroxy-deramciclane. a, FAB spectrum; b, CID spectrum of MH+ at m/z 318.

N-Desmethyl deramciclane was present in hepatocytes of all species investigated. Chromatographic and mass spectrometric behavior of the demethylated derivative was identical to that of the authentic reference compound.

Several hydroxylated derivatives of deramciclane were isolated mainly from the extracellular matrix in free or conjugated forms. Although the protonated molecular ion at m/z 318 was characteristic of all hydroxy-deramciclane compounds, three types could be distinguished by MS/MS (CID) analysis. In the case of two types, the hydroxy-group was located at the camphor ring, which was confirmed by the presence of fragment ion at m/z 229 (cleavage of dimethylamino-ethanol side chain). The water loss from the m/z 229 (which resulted in m/z 211) indicated the location of the hydroxy-group at the camphor and not at the aromatic ring. In the case of the third type of hydroxy-deramciclane compounds, the masses of the CID fragments indicated hydroxylation at the dimethylamino-ethanol side chain. Finally, it must be mentioned that hydroxylation on the 4''-position of the phenyl-ring was ruled out on the basis of chromatographic properties of the authentic reference compound.

View larger version (42K): [in this window] [in a new window]   FIG. 3. Infrared spectrum of 9-hydroxy-deramciclane metabolite (top) and authentic reference compound (bottom) in vapor phase.

Type II of hydroxy-deramciclane metabolites involves the compounds for which one of the secondary carbon atoms of the camphor ring was hydroxylated (Fig. 4). The CID spectrum of m/z 318 with fragments at m/z 229, 169, and 156 predicted that the hydroxy-group was likely to locate at the 5- or 6-position.

View larger version (34K): [in this window] [in a new window]   FIG. 4. Mass spectrometric behavior of hydroxy-deramciclane II. a, FAB spectrum; b, CID spectrum of MH+ at m/z 318.

Rat and human hepatocytes were proven to be able to produce deramciclane N-oxide. Chromatographic and mass spectrometric properties of the isolated metabolite were identical to that of authentic reference compound. The chromatographic mobility of deramciclane N-oxide standard was rather slow in ethyl acetate/triethylamine (25:1 v/v)—it ran close to the start point (M1 spot of Fig. 1)—but it could be separated on a thin-layer plate in butanol/acetic acid/water (4:1:1 v/v). The results of MS/MS analysis (MH⁺ at m/z 318 and fragments at m/z 213 and 106) provided the evidence that the skeleton of deramciclane remained unchanged, whereas the side chain involved one more oxygen suspected to form N-oxide.

Hydroxylation of N-desmethyl deramciclane also occurred at several positions of the molecule. The structures of N-desmethyl 8- or 9-hydroxy-deramciclane were determined by MS/MS after isolation from thin layer. Thin-layer or gas chromatographic properties and mass spectrometric behavior of N-desmethyl 9-hydroxy-deramciclane metabolite (R_f 0.115 in butanol/acetic acid/water) were identical to those of the authentic reference compound. Thus, the spot with an R_f of 0.262 was supposed to contain N-desmethyl 8-hydroxyderamciclane. GC-MS analysis of the extracts proved the presence of one more N-desmethyl hydroxy-deramciclane metabolite that was produced by the hepatocytes of all species investigated. The results of mass spectrometric measurement made it clear that N-desmethyl-deramciclane underwent hydroxylation at one of the secondary carbons of the camphor ring.

Among hydroxylated derivatives of deramciclane, there were two dihydroxylated metabolites with different chromatographic mobilities in butanol/acetic acid/water, but identical mass spectrometric properties (Table 1). The results of MS/MS analysis supported the assumption that one of the hydroxy-group was located at the camphor ring, whereas the other was at the side chain. The exact mass measurement also confirmed the structure of dihydroxy-deramciclane metabolites as C₂₀H₃₂O₃N (MH⁺ = 334.2382) and of the side chain as C₄H₁₂O₂N (m/z 106 fragment = 106.0868).

Using a butanol/acetic acid/water solvent delivery system, two carboxy-derivatives of deramciclane could be separated, which were produced by oxidation of one of the methyl-groups of the camphor ring to carboxylic acid. Furthermore, N-demethylation and oxidation to carboxylic acid resulted in N-desmethyl carboxy-deramciclane with the molecular ion (MH⁺) at m/z 318 and fragment ions at m/z 243 and 76 (as a result of the cleavage of monomethyl amino-ethanol side chain). Although it was identical to the molecular ion of hydroxy-deramciclane derivatives, the latter could be distinguished on the basis of CID spectra.

The cleavage of the total side chain of deramciclane resulted in the formation of phenylborneol as it was identified on the basis of chromatograhic properties of the authentic standard. Although GC-MS analysis determined its structure as phenylcamphene and phenylbornylene, that determination might be due to the chemical modification of phenylborneol (loss of water) during the isolation from the thin-layer plate or GC procedures. Since the authentic reference compounds for phenylborneol, phenylbornylene, and phenylcamphene had the same R_f values in both mobile phases used, the correct separation had to be developed in n-hexane/chloroform (1:1 v/v). The radiodensitogram confirmed that the metabolite produced during deramciclane biotransformation was neither phenylbornylene nor phenylcamphene, but most probably phenylborneol. The spot with an R_f of 0.720 (in butanol/acetic acid/water) also contained hydroxy-phenylborneol as a product of rat hepatocytes.

View larger version (21K): [in this window] [in a new window]   FIG. 5. Proposed metabolic scheme for deramciclane.

	Discussion

Top Abstract Materials and Methods Results Discussion References

The proposed metabolic scheme for biotransformation of deramciclane based on the results of this study is depicted in Fig. 5. Oxidative metabolism of deramciclane occurred on the ring of camphor and/or on the side chain, but the aromatic ring remained unchanged. Primary routes of metabolism in all species were N-demethylation and hydroxylation of the molecule. N-Demethylation does not result in pharmacological deactivation of deramciclane. N-Desmethyl-deramciclane has been reported to have receptor-binding characteristics and pharmacological activity similar to those of the parent compound. Previous studies proved that N-desmethyl deramciclane was also formed in vivo in several animal species (Kanerva et al., 1998; Nemes et al., 2000; Magyar et al., 2002) and in humans (Huupponen et al., 2004).

Both deramciclane and N-desmethyl deramciclane were subjected to hydroxylation at different positions of the camphor part or the side chain. Camphor is known to undergo oxidative metabolism to form hydroxy-derivatives (Leibman and Ortiz, 1973; White et al., 1984; Sariaslani et al., 1990). In the case of deramciclane, several positional isomers of hydroxy-metabolites were also identified. 9-Hydroxy-deramciclane was produced in detectable amounts by the hepatocytes from all species investigated except for humans. Hydroxylation of the camphor ring at the 9-position was considered to be one of the major routes of deramciclane metabolism in rat, mouse, and rabbit hepatocytes, whereas dog cells formed 9-hydroxy-deramciclane as a minor metabolite. In contrast, 8-hydroxy-deramciclane was detected only in trace and solely in rat liver cells. As it is often observed with metabolites hydroxylated at primary carbon atoms of a xenobiotic, further oxidation to carboxylic acids was also observed in the case of deramciclane. From the fact that carboxy-deramciclane was produced by human hepatocytes, the formation of 9- or 8-hydroxy-deramciclane as an intermediate metabolite was also supposed. Hydroxylation at one of the secondary carbon atoms (at the 5- or 6-position) of the camphor ring also occurred. One of the hydroxy-deramciclane II metabolites, supposed to be 5-hydroxy-deramciclane, was produced by the hepatocytes from all species, whereas the 6-hydroxy derivative was formed only in rat cells. The major metabolite, N-desmethyl deramciclane, was subjected to further hydroxylation at primary or secondary carbon atoms of the camphor ring. Further oxidation of N-desmethyl deramciclane also resulted in the formation of N-desmethyl carboxy-deramciclane in rat and rabbit hepatocytes, possibly via the intermediate metabolites, N-desmethyl 9- or 8-hydroxy-deramciclane.

Our results showed that hydroxylation at the 1'-position of the side chain of deramciclane also occurred in rat and human cells. Furthermore, dihydroxylated derivatives with one hydroxy group at the side chain and the other at the camphor ring were also found in rat, rabbit, and dog hepatocytes, but not in human hepatocytes. Oxidation of the side chain at the nitrogen led to the formation of a considerable amount of deramciclane N-oxide in rat and human cells. It should be noted that sequential metabolism of N-oxide was not observed. Phenylborneol due to the cleavage of the total side chain of deramciclane was formed as a minor metabolite in hepatocytes isolated from all species investigated. However, water loss leading to phenylbornylene and phenylcamphene was excluded in all species. The amount of phenylborneol can be supposed to be reduced by sequential metabolism to hydroxy-phenylborneols. Hydroxy-phenylborneol formation was proved in rat hepatocytes.

Glucuronide conjugation of hydroxy-deramciclane derivatives seemed to be facile in rat, rabbit, and dog liver cells. However, there was no indication for the presence of glucuronide conjugates in mouse or human hepatocytes.

One of the main goals of comparative metabolic studies is considered to be their appropriateness for selecting the best animal model(s) for preclinical toxicology studies on the basis of qualitative similarity in metabolic profile to human models. The profiles of deramciclane metabolites in the hepatocytes isolated from several laboratory animals and humans were not exactly the same across species. Although we highlighted species differences in deramciclane metabolism, it was concluded that phase I metabolism in human liver cells seemed to be similar to the metabolism in rat hepatocytes. Phase I metabolites isolated and identified from human hepatocytes were also produced by rat cells. With careful approach, the rat model may be considered to be predictive for human metabolism of deramciclane.

	Acknowledgments

 
We express our thanks to EGIS Pharmaceuticals Ltd. (Budapest, Hungary) for providing the authentic reference compounds used in this study.

	Footnotes

 
Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.

doi:10.1124/dmd.105.003764.

ABBREVIATIONS: deramciclane, (1R,2S,4R)-(–)-2-phenyl-2-(2'-dimethylamino-ethoxy)-1,7,7-trimethyl-bicyclo[2.2.1]heptane; N-desmethylderamciclane (M4), (1R,2S,4R)-(–)-2-phenyl-2-(2'-methylamino-ethoxy)-1,7,7-trimethyl-bicyclo[2.2.1]heptane; 9-hydroxy-deramciclane (M5), (1R,2S,4R,7R)-2-(2'-dimethylamino-ethoxy)-2-phenyl-7-(hydroxy-methyl)-1,7-dimethyl-bicyclo[2.2.1]heptane; deramciclane N-oxide, (1R,2S,4R)-(–)-2-phenyl-2-(2'-dimethylamino-ethoxy)-1,7,7-trimethyl-bicyclo[2.2.1]heptane-N-oxide; hydroxy-deramciclane II (M6), (1R,2S,4R)-(–)-2-phenyl-2-(2'-dimethylamino-ethoxy)-5 or 6-hydroxy-1,7,7-trimethyl-bicyclo[2.2.1]heptane; N-desmethyl 9-hydroxy-deramciclane (M2), (1R,2S,4R,7R)-2-(2'-methyl-amino-ethoxy)-2-phenyl-7-(hydroxy-methyl)-1,7-dimethyl-bicyclo[2.2.1]heptane; N-desmethyl hydroxy-deramciclane II (M3), (1R,2S,4R)-(–)-2-phenyl-2-(2'-methylamino-ethoxy)-5 or 6-hydroxy-1,7,7-trimethyl-bicyclo[2.2.1]heptane; phenylborneol (M8), (1R,2S,4R)-(–)-2-hydroxy-2-phenyl-1,7,7-trimethyl-bicyclo[2.2.1] heptane; phenylbornylene, (1S,4R)-2-phenyl-1,7,7-trimethyl-bicyclo[2.2.1]hept-2-ene; phenylcamphene: 3,3-dimethyl-2-methylene-1-phenyl-bicyclo[2.2.1]heptane; 4''-hydroxy-deramciclane: (1R,2S,4R)-(–)-2-(4''-hydroxy-phenyl)-2-(2'-dimethyl-amino-ethoxy)-1,7,7-trimethyl-bicyclo[2.2.1]heptane; CID, collision-induced decomposition; FAB, fast-atom bombardment; GC-MS, gas chromatography/mass spectrometry; MS/MS, tandem mass spectrometry.

Address correspondence to: Katalin Monostory, P.O. Box 17, Budapest, H-1525 Hungary. E-mail address: monostor{at}chemres.hu

	References

Top Abstract Materials and Methods Results Discussion References

 


Bayliss KM and Skett P (1996) Isolation and culture of human hepatocytes, in Human Cell Culture Protocols (Jones GE ed) pp 369–390, Humana Press, Totowa, NJ.

Berényi E, Blaskó G, Fekete M, and Nógrádi M (1990) EGYT-3886. Drugs Future 15: 1174–1175.

Berry MN, Edwards AM, Barritt GJ, Grivell MB, Halls HJ, Gannon BJ, and Friend DS (1991) Initial determination of cell quality, in Isolated Hepatocytes (Berry MN, Barrit GJ, and Edwards AM eds) pp 45–47, Elsevier, Amsterdam.

Ferrini JB, Ourlin JC, Pichard L, Fabre G, and Maurel P (1998) Human hepatocyte culture, in Cytochrome P450 Protocols (Phillips IR and Shephard EA eds) pp 341–352, Humana Press, Totowa, NJ.

Gacsályi I, Gyertyán I, Petcz L, and Budai Z (1988) Psychopharmacology of a new anxiolytic agent EGYT-3886. Pharmacol Res Commun 20 (Suppl I): 115–116.

Gillette JR (1995) Keynote address: man, mice, microsomes, metabolites and mathemathics 40 years after the revolution. Drug Metab Rev 27: 1–44.[Medline]

Guengerich FP (1993) Metabolic reactions: types of reactions of cytochrome P450 enzymes, in Handbook of Experimental Pharmacology: Cytochrome P450 vol 105 (Born GVR, Cuatrecasas P, and Herken H eds) pp 89–103, Springer-Verlag, Berlin.

Guengerich FP (1996) The chemistry of cytochrome P450 reactions, in Cytochrome P450: Metabolic and Toxicological Aspects (Ioannides C ed) pp 55–74, CRC Press, New York.

Hollenberg PF (1992) Mechanisms of cytochrome P450 and peroxidase-catalyzed xenobiotic metabolism. FASEB J 6: 689–694.

Huupponen R, Anttila M, Rouru J, Kanerva H, Miettinen T, and Scheinin M (2004) Pharmacokinetics of deramciclane and N-desmethylderamciclane after single and repeated oral doses in healthy volunteers. Int J Clin Pharmacol Ther 42: 449–455.[Medline]

Kanerva H, Huuskonen H, Alhonen-Raatesalmi A, Nevalainen T, and Urtti A (1998) Pharmacokinetics of deramciclane in dogs after single oral and intravenous dosing and multiple oral dosing. Biopharm Drug Dispos 19: 531–539.[Medline]

Klebovich I, Kanerva H, Bojti E, Urtti A, and Drabant S (1998) Comparative pharmacokinetics of deramciclane in rat, dog, rabbit and man after the administration of a single oral dose of 3 mg kg^{– 1}. Pharm Pharmacol Commun 4: 129–136.

Kovács I, Maksay G, and Simonyi M (1989) Inhibition of high-affinity synaptosomal uptake of -aminobutyric acid by a bicyclo-heptane derivative. Arzneim-Forsch/Drug Res 39: 295–297.

Leibman KC and Ortiz E (1973) Mammalian metabolism of terpenoids. I. Reduction and hydroxylation of camphor and related compounds. Drug Metab Dispos 1: 543–551.[Abstract]

Ludányi K, Gömöry Á, Klebovich I, Monostory K, Vereczkey L, Újszászy K, and Vékey K (1997) Application of TLC-FAB mass spectrometry in metabolism research. J Planar Chromatogr 10: 90–96.

Magyar K, Lengyel J, Bolehovszky A, Grezal G, and Klebovich I (2002) Studies of the side chain cleavage of deramciclane in rats with radiolabelled compounds. Eur J Pharm Sci 15: 217–223.[Medline]

Maurel P (1996) The use of adult human hepatocytes in primary culture and other in vitro systems to investigate drug metabolism in man. Adv Drug Deliv Rev 22: 105–132.[CrossRef]

Nemes KB, Abermann M, Bojti E, Grezal G, Al-Behaisi S, and Klebovich I (2000) Oral, intraperitoneal and intravenous pharmacokinetics of deramciclane and its N-desmethyl metabolite in the rat. J Pharm Pharmacol 52: 47–51.[Medline]

Palvimaki EP, Majasuo H, Kuoppamaki M, Mannisto PT, Syvalahti E, and Hietala J (1998) Deramciclane, a putative anxiolytic drug, is a serotonin 5-HT2C receptor inverse agonist but fails to induce 5-HT2C receptor down-regulation. Psychopharmacology 136: 99–104.[CrossRef][Medline]

Sariaslani FS, McGee LR, and Trower MK (1990) Lack of regio- and stereospecificity in oxidation of (+)camphor by Streptomyces griseus enriched in cytochrome P-450_soy. Biochem Biophys Res Commun 170: 456–461.[Medline]

Vermeulen NPE (1996) Role of metabolism in chemical toxicity, in Cytochrome P450: Metabolic and Toxicological Aspects (Ioannides C ed) pp 29–53, CRC Press, New York.

White RE, McCarthy MB, Egeberg KD, and Sligar SG (1984) Regioselectivity in the cytochrome P-450: control by protein constraints and by chemical reactivities. Arch Biochem Biophys 228: 493–502.[CrossRef][Medline]

This article has been cited by other articles:

				K. Monostory, K. Kohalmy, E. Hazai, L. Vereczkey, and L. Kobori ROLE OF CYP2E1 IN DERAMCICLANE METABOLISM Drug Metab. Dispos., November 1, 2005; 33(11): 1717 - 1722. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) All Versions of this Article: dmd.105.003764v1 33/11/1708    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Monostory, K. Articles by Kóbori, L. Search for Related Content PubMed PubMed Citation Articles by Monostory, K. Articles by Kóbori, L.