Development of an efficient method of gene introduction to target cells is the key issue in treating genetic and acquired diseases by in vivo gene therapy. Although various nonviral approaches have been developed, any method needs to be optimized in terms of the target disease and transgene product. The most important information required is (i) target cell-specificity of gene transfer, (ii) efficiency, (iii) duration of transgene expression, and (iv) the number of transfected cells following in vivo application of a vector. These characteristics are determined by the properties of the vector used, as well as the route of its administration, biodistribution, interaction with biological components and the nature of the target cells. Cell-specific gene transfer can be achieved by controlling the tissue disposition of plasmid DNA (pDNA), although the interaction of the pDNA complex with biological components might limit the specificity. Various approaches have been reported to increase the efficiency of transgene expression, from cationic lipids/polymers to physical stimuli, but some of those are ineffective under in vivo conditions. The duration of transgene expression is a complex function involving variables including the cell type, transfection method, and plasmid construct. Immune response often reduces the level and duration of transgene expression. In addition, the number of transfected cells is important, especially in cases in which the therapeutic protein localizes within the target cells. Successful clinical application of nonviral gene delivery methods rely on the development of such methods optimized for a particular target disease.
In Parkinson's disease, while dopamine (DA) replacement therapy, such as with L-DOPA (levodopa), improves the symptoms, it does not inhibit the degeneration of DA neurons in the substantia nigra. Numerous studies have suggested that both endogenous and environmental neurotoxins and oxidative stress may participate in this disease, but the detailed mechanisms are still unclear. Recent genetic studies in familial Parkinson's disease and parkinsonism have shown several gene mutations. This new information regarding its pathogenesis offers novel prospects for effective strategies involving the neuroprotection of vulnerable DA neurons. This review summarizes current findings regarding the pathogenesis and antiparkinsonian drugs, and discusses their possibilities of targets to develop novel neuroprotective drugs.
The Na+-dependent transport of L-glutamate (GluT) has been identified in brain tissue more than thirty years ago. Neurochemical studies, performed in various experimental models during 1970's, defined the basic rules for the selection or synthesis of GluT-specific substrates and inhibitors. The protein molecules (transporters) that mediate the translocation of the substrates across the plasma membrane have been cloned and studied during the last ten years. The sites on the transporters that bind the substrates favour glutamate-like or aspartate-like molecules with one positively charged and two negatively charged ionised groups. Substituents at C3 and C4 are often tolerated but substitutions at C2 or alterations of the ionisable groups usually impede the binding. The substrate binding sites display an “anomalous” selectivity towards stereoisomers. These structural requirements are shared by all Na+-dependent glutamate transporters thus making the design of transporter-selective ligands a challenging task. Moreover, the molecular mechanisms of the transport have not yet been adequately elucidated. Data from a wide variety of experimental studies strongly indicate that Na+-dependent GluT regulates the functioning of the glutamatergic excitatory synapses—the most important rapid inter-neuronal signalling system in the mammalian brain. Altered structural and/or functional properties of the Na+-dependent glutamate transporters have been implicated in the damage to the brain tissue following cerebral ischaemia and in the progressive loss of neurons in conditions such as Alzheimer dementia and amyotrophic lateral sclerosis. Furthermore, it seems that fine-tuning of glutamatergic neurotransmission by regulating the Na+-dependent GluT could be useful in the therapy of schizophrenia.
An ionspray ionization mass-spectrometric method for the determination of N1,N12-diacetylspermine (Ac2Spm) was developed using 15N-labeled Ac2Spm as the internal standard. Concentrations of Ac2Spm in the urine obtained from 17 cancer patients measured by the present method correlated well with those measured by ELISA, showing the usefulness of the two methods.
Mevalonate pyrophosphate decarboxylase (MPD) in mouse liver was purified by affinity chromatography. The purified enzyme was a homodimer of 46-kDa subunits and had an isoelectric point of 5.0. Kinetic analysis revealed an apparent Km value of 10 μM for mevalonate pyrophosphate. The enzyme required ATP as a phosphate acceptor and Mg as a divalent cation, which could be substituted with Mn or Co. Its optimum pH was 4.0—7.0. A comparison with MPD from various other sources revealed the mouse MPD to have essentially the same properties as rat MPD, expect for the optimum pH range. An excess of rabbit anti-rat MPD antibody deleted approximately 80% of the MPD activity in the crude extract of mouse liver. These results suggested that the homodimer of 46-kDa subunits represents the major active form of MPD in mice.
Beta-amyloid peptide 1—42 is a major peptide constituent of β-amyloid fibrils. We investigated the role of sucrose on the deposition and the D-aspartic acid formation in an amyloidogenic peptide 1—42 under physiological conditions. From analyses using thioflavine-T fluorometric assay and electronmicroscopic spectroscopy after 60 h incubation at 37 °C, it was found that sucrose retarded the fibril formation in the amyloidogenic peptide. The retardation of the formation of amyloid fibrils by sucrose was suggested to be not due to viscosity but due to disturbance of the assemlby of α-helix containing peptides. Moreover, we showed that the formation of D-aspartyl residue, which is found in β-amyloid fibrils from Alzheimer disease brains, in the amyloidogenic peptide was also retarded in the presence of sucrose.
To elucidate the biological significance of extracellular adenine compounds, the effects of adenosine (Ado) on cellular levels of adenine compounds, especially adenosine triphosphate (ATP), in PC12 cells were studied. Ado and inosine but not adenosine 5′-monophosphate, adenosine 5′-diphosphate, ATP, guanosine, cytosine, thymidine, and uridine, significantly enhanced cellular ATP levels in PC12 cells in time- and dose-dependent manners. Various P1 receptor agonists of Ado did not enhance the ATP level. In addition, theophylline, an antagonist of P1 receptors, did not inhibit the Ado-evoked ATP enhancement. These results suggest that the Ado receptor is not involved in the augmentation of the cellular ATP level induced by Ado in PC12 cells. The ATP-enhancing effect of Ado was potentiated by dipyridamole, an inhibitor of Ado uptake, or coformycin, an inhibitor of Ado deaminase. The effect of Ado on the ATP level was also observed when PC12 cells were incubated in glucose-free medium. Together these results suggest that enhancement of cellular ATP levels in PC12 cells by extracellular Ado might be acceleration of ATP synthesis through the Ado salvage system using hypoxanthine-guanine phosphoribosyltransferase rather than Ado kinase since 5′-iodotubercidin, an inhibitor of Ado kinase, had no effect on the enhancement elicited by Ado.
Our previous study demonstrated that the smallest synthetic peptide with the sequence CPVHLKRLLLLLLLLLLLLLLLL, SP-CL16(6—28), admixed with phospholipid (synthetic lung surfactant, SLS) showed strong surface activity. In this study, we attempted to develop a dual-type surfactant with both anti inflammatory and surface activities. SP-CL16(6—28) was first chemically synthesized and then purified for use by centrifugal partition chromatography. A mixture of SP-CL16(6—28) and phospholipid complex was tested for anti inflammatory activity using the human monocyte cell line THP-1. Whether the suppression of tumor necrosis factor-α (TNF-α), interleukin (IL)-8, IL-6, IL-1β, and macrophage migration inhibitory factor (MIF) was reduced by lipopolysaccharide (LPS) in monocytes was examined. Levels of these cytokines were measured by enzyme-linked immunosorbent assay. It was found that SLS significantly and dose dependently inhibited the secretion of TNF-α by THP-1 cells following stimulation with LPS. Dipalmitoylphosphatidylcoline did not inhibit the release of cytokines. These findings suggest that SLS has anti inflammatory activity. Therefore it should be possible to develop a SLS with both anti inflammatory activity and surface activity.
Interleukin (IL)-5 is thought to play important roles in asthma and to be a potential therapeutic target. An intratracheal injection of murine recombinant IL-5 (3—30 μg/animal) induced a dose-dependent increase in the number of eosinophils in the bronchoalveolar lavage fluid of Brown Norway (BN) rats 24 h after administration. Bovine serum albumin (30 μg/animal), used as reference material, did not cause any change. The reaction was not observed in F344 rats. The increase in the number of eosinophils did not accompany bronchial hyperreactivity in BN or F344 rats. Prednisolone (3—10 mg/kg, i.p.) and emedastine (30 mg/kg, p.o.) reduced the increased number of eosinophils induced by the IL-5 challenge. These results suggest that IL-5 is a potent inducer of eosinophils in the airway of BN rats. Prednisolone and emedastine are effective against IL-5-induced eosinophilia.
Effects of Mn2+ on isolated guinea pig ventricular myocardia were examined. In isolated papillary muscles, Mn2+ produced a transient decrease in contractile force followed by a late sustained augmentation. Mn2+ markedly increased the amplitude of post-rest contractions; the time course of potentiation was almost the same as that of the late augmentation of contractile force after Mn2+ application. Mn2+ also increased the amplitude of rapid-cooling contractures. The negative inotropic effect of diltiazem and nicardipine was not affected by the presence of Mn2+. Mn2+ shortened the action potential duration under normal condition whereas it prolonged the duration under Ca2+ free conditions. Mn2+, when applied to fura-2-loaded ventricular myocytes, markedly quenched the cytoplasmic fluorescence excited at 360 nm wavelength. We concluded that Mn2+ not only causes a decrease in contractile force by blocking the L-type Ca2+ channel, but also enters the cytoplasm through the channel and produces late augmentation of the contractile force through enhancement of sarcoplasmic reticulum function.
Hange-shashin-to has been used for chronic hypofunction of the gastrointestinal tract and to improve functional abnormalities of the upper and lower gastrointestinal system. To determine whether the pharmacological effects of Hange-shashin-to are due to gut-regulatory peptide levels, we developed a sensitive and specific double-antibody enzyme immunoassay (EIA) for detecting motilin and also examined the levels of somatostatin-, motilin-, gastrin-, and vasoactive intestinal peptide (VIP)-immunoreactive substances (IS) in plasma from healthy subjects. We developed a sensitive (3.5 pg, 1.4 pg/well) and specific (carboxy-terminal region) EIA for motilin. A single oral administration of Hange-shashin-to 6.0 g caused significant increases somatostatin-IS (20—60 min), motilin-IS (40 min), and gastrin-IS (40—90 min) levels in plasma compared with levels in a placebo group. Hange-shashin-to had no significant effect on VIP-IS levels after single administration. These changes in hormone levels (somatostatin, motilin, and gastrin) might relate to normalization of the upper and lower gastrointestinal system by Hange-shashin-to.
We examined the effects of the histamine H2-receptor antagonist, lafutidine, on the levels of gastrointestinal peptides (somatostatin, calcitonin gene-related peptide (CGRP), gastrin, secretin, and motilin) in plasma from healthy subjects. After a single oral administration of lafutidine (10 mg), the plasma lafutidine level (186±13.4 ng/ml) was highest in the 60-min sample after administration and then the plasma level fell. Lafutidine caused significant increase in plasma somatostatin levels at 20 to 120 min and in CGRP levels at 40 to 120 min, compared with a placebo group. The physiological release of plasma secretin was reduced by administration of lafutidine, but the medicine did not alter the level of gastrin or motilin. These results suggest that the pharmacological effects of lafutidine on regulation of gastrointestinal functions closely relate to changes of somatostatin-, CGRP- and secretin-immunoreactive substance levels in human plasma.
An assay for computerized scoring of the DNA content of the protozoan Tetrahymena pyriformis has been used for the detection of toxic responses to cocaine, since DNA is responsible for the replication of the genetic material and also reflects closely the number of chromosomes in the nucleus. Thus, doubling of the number of chromosomes in a cell will also correspond to doubling of the DNA content and of the nuclear volume. Two chemical forms of cocaine were used, cocaine hydrochloride and cocaine freebase (crack), at two doses of 1 and 2 mg per 100 ml of protozoan culture, respectively. Image analysis of the protozoan nucleus patterns revealed a rapid stimulating effect on the DNA content for both cocaine hydrochloride and freebase after 1 h of incubation. However, after 2 h of treatment a reduction, although not statistically significant, of the DNA content of the protozoan was observed. These observations were further correlated with the phagocytic activity of the protozoan cultures. This paper provides some possible explanations of the toxic effects of cocaine on this particular cell model.
To explore the physiological roles of cytochrome P450 (CYP) in peripheral blood cells, we examined which isoforms of CYP families were expressed in human myeloid leukemia cell lines (U937, HL-60 and K562) and lymphoid cell lines (BALL-1, MOLT-4 and Jurkat) by RT-PCR. We observed relatively high expression of CYP1A1, CYP1B1, CYP2A6, CYP2A7, CYP2D6, and CYP2E1 in all cell types, but CYP2A13 and CYP2C9 expression was not detected. Expressions of aryl hydrocarbon (Ah) receptor and Ah receptor nuclear translocator (ARNT), which mediate induction of the CYP1 family, were also detected in all cell types. Cell-type specific expression of CYP3A4 and CYP3A5 was observed in MOLT-4 and K562 cells. Weak, but significant, expression of CYP3A7 was detected in K562 cells. The profile of CYP expression in the culture cells reported here provides information that furthers our understanding of the physiological roles of CYP enzymes in human blood cells.
Pharmacological studies were carried out to characterize further the endocrinological profile and the binding mode to the estrogen receptor (ER) of 6,12-dihydro-3-methoxy-1-benzopyrano[3,4-b][1,4]benzothiazin-6-one (1). Binding experiments were conducted with highly purified recombinant human estrogen receptors hERα and β. Potent estrogenic activity of compound 1 was assessed by testing its ability to down-regulate ERs and to enhance estrogen receptor element (ERE)-dependent transcription. The latest step of our work dealt with the synthesis of the 9-fluorinated derivative 15 for ionic microscopy experiments to determine the intracellular localization of compound 1. Although 1 failed to compete with [3H]E2 for binding to both ER isoforms, evidence was reported that it interacted with hERα in MCF-7 cells (ER down-regulation/ERE-dependent luciferase induction). Hence, an appropriate conformation of the hormone binding domain, most probably conferred by co-regulators of ER, is required for the onset of an activity of the compound 1. Estrogenic activity was weak but on the order of magnitude of that of coumestrol (slightly weaker). The synthesis of the 9-methoxylated derivative 16 and its pharmacological evaluation led us to propose a binding mode of 1 on hERα. Compound 1 appears to interact with ERα mainly through interactions of its 3-methoxy substituent with the residue His-524 of the hormone binding domain.
In this study the anti-proliferative effect of curcumin (curcuma longa) that is the active ingredient of ground dried rhizome has been studied against three local and three reference leishmanial strains, Leishmania major, Leishmania tropica and Leishmania infantum (Pakistani isolate). Curcumin has shown an average IC50 of 5.3 μM against promastigotes of various leishmanial strains which is much lower as compared with pentamidine that is one of the basic treatments against leishmaniasis. The main draw back attributed to these assays performed on promastigotes is the heterogeneity of results compared with those obtained with intracellular amastigotes or with in vivo effect. We also tested activity of curcumin against axenic amastigote like cells (AALC) of L. major strain (MHOM/PK/88/DESTO). Curcumin proves to be far more potent then pentamidine against AALC which further strengthens the fact about its leishmaniacidal activity.
We previously reported that zeaxanthin dipalmitate (ZD), a carotenoid from Lycium chinense fruit, reduces myofibroblast-like cell proliferation and collagen synthesis in vitro. To determine whether ZD might reduce the severity of hepatic fibrosis in an animal model, hepatic fibrosis was induced in rats by bile duct ligation/scission (BDL) for a period of 6 weeks. Treatment of BDL rats with ZD at a dose of 25 mg/kg body weight significantly reduced the activities of aspartate transaminase (p<0.05) and alkaline phosphatase (p<0.001) in serum. Furthermore, collagen deposition was significantly reduced as assessed by the Sirius Red binding assay in BDL rats administered ZD at the dose of 25 mg/kg body weight (p<0.01). In addition, the levels of thiobarbituric acid-reactive substances and 4-hydroxyproline were reduced when BDL rats received ZD at the dose of 25 mg/kg body weight. These results showed that ZD effectively inhibited hepatic fibrosis in BDL rats, at least in part via its antioxidative activity.
The transdermal therapeutic systems (TTS) usually achieve constant plasma concentration for an extended period of time. This is because a sufficient drug stored in the device can keep the constant concentration on the surface of the stratum corneum during the system application. When the drug molecules are not enough to provide the constant surface concentration, the rate of drug penetration decreases with time because of decreased supply of the drug molecules from the delivery device. This paper has proposed an empirical simple approach to predict the plasma concentration for such a TTS. A novel compound, GTS-21, for Alzheimers' disease currently under development was used as a model drug. In vivo and in vitro experiments were carried out in hairless rats. The in vivo plasma concentration–time profile in hairless rats following the application of TTS well agreed with the predicted profile based on the skin pharmacokinetic model together with the model parameters determined from the in vitro experiment.
Purpose of the present study was to evaluate the myopathy risk using a urethane infusion method following oral administration of five kinds of commercial HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme A) reductase inhibitors (HCRIs), (pravastatin (PV), simvastatin (SV), cerivastatin (CeV), atorvastatin (AV), and fluvastatin (FV)) alone or with coadministration of bezafibrate (BF). The solubility of HCRIs in various solvents was determined as a criterion of the physicochemical property. The plasma creatine phosphokinase (CPK) level as a marker of myopathy in normal rats was screened under urethane infusion after oral administration of HCRI alone or with BF coadministration. Also, renal tissue specimens were prepared and the myoglobin remaining in the tissue was visualized by the labeled avidin-biotin technique. The plasma CPK level in normal rats under urethane infusion following oral administration of five kinds of HCRI increased as the dose of HCRI increased, and coadministration of BF further increased the CPK level for each drug. The risk of myopathy evaluated from the CPK level was ranked as follows: CeV>FV>AV>SV>PV. Myoglobin deposition was observed in the cast of proximal tubules, cytoplasm of distal tubules and collecting ducts of rat kidney extracted from rats treated with HCRIs under urethane infusion. Histopathological findings showed that the extent of myoglobin deposition increased on coadministration of BF with each drug. The correlation was found for myopathy risk evaluated by CPK level using the urethane infusion method and drug lipophilicity, i.e., the water/n-octanol partition coefficient except for the case of SV. Histopathological findings for the kidney following HCRI treatment also reflected the CPK level in rats under urethane infusion.
CpG oligodeoxynucleotides (CpG-ODN) could be expectes to act as an adjuvant for humoral and cellular immunities. The aim of this study was to clarify the mechanism of macrophage activation induced by CpG-ODN. Macrophage activation by CpG-ODN was evaluated by measurement of IL-12 secretion. IL-12 secretion by Cp-ODN was dose-dependent and saturation was observed at 1 μM. A reactive oxygen species (ROS) scavenger, N-acetylcysteine, inhibited IL-12 secretion, suggesting that the intracellular redox state is important for the activation of macrophages by CpG-ODN. IL-12 secretion was also inhibited by NADPH–oxidase inhibitors, suggesting that ROS generated by NADPH–oxidase is involved in the immunostimulatory effect of CpG-ODN. Nuclear factor (NF)-κB is one of the transcriptional factors involved in IL-12 gene expression, and indeed CpG-ODN activated NF-κB. However, NADPH–oxidase inhibitors did not affect the activation. These results indicated that NADPH–oxidase plays a crucial role in macrophage activation by CpG-ODN and NF-κB does not act as a predominant transcription factor for IL-12 secretion.
Several anionic proteins that are known to be substrates of scavenger receptors documented in the literature were selected and tested for their effects on the uptake of fractionated heparin (FH), an anionic macromolecular drug. The tests were made in rat liver parenchymal cells to characterize scavenger-like receptors involved in FH uptake, probing into substrate recognition characteristics in comparison with those of scavenger receptors. Although the uptake of FH was completely inhibited by dextran sulfate, a typical substrate of scavenger receptors, suggesting that scavenger-like receptors that have affinity for some anionic macromolecules are responsible for the uptake, it was not inhibited by acetylated low density lipoprotein (Ac-LDL), another typical substrate. Thus, the scavenger-like receptors were suggested to be different from the major scavenger receptors of classes A and B that are known to be sensitive to Ac-LDL. The uptake of FH was only partially inhibited by maleylated bovine serum albumin (Mal-BSA), suggesting that the scavenger-like receptors can be classified into two types in terms of sensitivity to Mal-BSA. The Mal-BSA-sensitive receptor was also found to be sensitive to oxidized low density lipoprotein (Ox-LDL). Kinetic analysis revealed that the binding capacity (Bmax) of the Mal-BSA-insensitive receptor was significantly larger than that of the Mal-BSA-sensitive one, though their dissociation constants (Kd) and apparent internalization rate constants (kint, app) were comparable. Information obtained in this study should be helpful for understanding the disposition mechanism of FH and also of anionic macromolecules and for developing delivery strategies, although the physiological roles and molecular identity of each receptor need to be further clarified in the future.
This study was carried out to develop a novel method for predicting the skin permeability coefficient (log Kp) of compounds from their three-dimensional molecular structure using a combination of molecular orbital (MO) calculation and artificial neural network. Human skin permeability data on 92 structurally diverse compounds were analyzed. The molecular descriptors of each compound, such as the dipole moment, polarizability, sum of charges of nitrogen and oxygen atoms (sum(N, O)), and sum of charges of hydrogen atoms bonding to nitrogen or oxygen atoms (sum(H)) were obtained from MO calculations. The correlation between these molecular descriptors and log Kp was examined using feed-forward back-propagation neural networks. To improve the generalization capability of a neural network, the network was trained with input patterns given 5% random noise. The neural network model with a configuration of 4–4–1 for input, hidden, and output layers was much superior to the conventional multiple linear regression model in terms of root mean square (RMS) errors (0.528 vs. 0.930). A “leave-one-out” cross-validation revealed that the neural network model could predict skin permeability with a reasonable accuracy (predictive RMS error of 0.669).
We recently reported that P-glycoprotein (MDR1) is capable of interfering with the absorption of methylprednisolone in the rat small intestine. This study was undertaken to examine the interaction between methylprednisolone and MDR1 using Caco-2 cells. The permeation of various steroid hormones (hydrocortisone, prednisolone, progesterone, β-estradiol, and testosterone) was compared. The basolateral-to-apical (secretory) permeation of methylprednisolone was more than 3-fold greater than the apical-to-basolateral (absorptive) permeation. When verapamil (0.1 mM), a potent modulator of MDR1, was added to both apical and basolateral sides of Caco-2 cells, the absorptive permeation of methylprednisolone was increased and its secretory permeation was decreased. As a result, the secretory-oriented manner of methylprednisolone permeation almost completely disappeared. Prednisolone and hydrocortisone exhibited weaker secretory-oriented movement than did methylprednisolone. The secretory-oriented permeation of prednisolone and hydrocortisone was also diminished by the addition of verapamil. There was no significant directionality in progesterone permeation and the permeation of β-estradiol and testosterone tended to be absorptive. These results appear to suggest that methylprednisolone, prednisolone, and hydrocortisone interact with MDR1 as the substrates. In contrast, there was no evidence that MDR1 was capable of potently interfering with the absorption of the sex hormones tested in this study, supporting our previous findings in the rat. It was further found that apically-added verapamil demonstrated a modulating effect on MDR1 function even at 5 μM.
The crude polysaccharide (PFB-1) was isolated from the leaves of Perilla frutescens var. crispa by the sequential procedures with hot-water extraction, methanol reflux, and ethanol precipitation. It was further purified by anion column chromatography in order to obtain the partially purified polysaccharide (PFB-1-0). In the presence of PFB-1-0, strong cellular lysosomal enzyme activity of murine peritoneal macrophages was observed in vitro. Compared to bacterial lipopolysaccharide (LPS), its activity was relatively high. The in vitro phagocytic activity was enhanced by PFB-1-0 as the similar pattern in both gram-negative bacteria, E. coli, and gram-positive bacteria, S. aureus with a time-dependent manner. We also investigated the production of several mediators by murine peritoneal macrophages upon stimulation with PFB-1 (in vivo) or PFB-1-0 (in vitro). The levels of nitric oxide (NO) and tumor necrosis factor (TNF)-α were increased in the presence of PFB-1-0 in vitro. The PFB-1 stimulated the production of interleukin (IL)-6 and granulocyte-macrophage colony-stimulating factor (GM-CSF) in vivo. Results suggest that the polysaccharide from P. frutescens var. crispa represents an immunopotentiator and biological response modifiers in vitro and in vivo levels.
It was demonstrated that trans-stilbene was metabolically activated to the estrogenic compound by rat liver microsomes (Sugihara et al., Toxicol. Appl. Pharmacol., 167, 46—54 (2000)). In this study, determination of the isoforms of cytochrome P450 involved in the oxidation of the proestrogen, trans-stilbene, to its hydroxylated metabolites was examined. When trans-stilbene was incubated with rat liver microsomes in the presence of NADPH, estrogenic compounds, trans-4-hydroxystilbene and trans-4,4′-dihydroxystilbene were formed. Comparison of the oxidase activity among liver microsomes of untreated, 3-methylcholanthrene-treated, acetone-treated, clofibrate-treated, dexamethasone-treated and phenobarbital-treated rats toward trans-stilbene showed that those from 3-methylcholanthrene-treated rats exhibited the highest activity. Human liver microsomes also catalyzed the oxidation in varying degrees. Variation in trans-stilbene oxidase activity was closely correlated to that of phenacetin O-deethylase activity. The oxidase activity was inhibited by α-naphthoflavone; however, in this case trans-4,4′-dihydroxystilbene was not detected. The oxidase activity toward trans-stilbene was exhibited by recombinant human cytochrome P450 1A1 and 1A2 expressed in a human B lymphoblastoid cell line.