Drug-metabolizing Enzymes In Mice Research Articles

Effects of Fasting and Phoenix dactylifera on the Expression of Major Drug- Metabolizing Enzymes in the Mouse Livers.

This study aimed to investigate the effects of consuming Phoenix dactylifera and fasting on the mRNA expression of major hepatic drug-metabolizing enzymes in mice. Phoenix dactylifera ethanolic extract was analyzed using LC-MS/MS. We used forty-two male Balb/c mice, which were treated with low (300 mg/kg) and high (2583 mg/kg) doses of Phoenix dactylifera and fasted for 24 hours, two weeks, and one month. Then, we analyzed the expression of cyp3a11, cyp2c29, cyp2d9, and ugt2b1 using real-time polymerase chain reaction assay. In addition, we assessed the relative liver weights of the mice and the hepatic phathohistological alterations. We found that Phoenix dactylifera ethanolic extract contained 38 phytochemical compounds, mainly kaempherol, campesterol, lutein, apigenin, genistein, and isoquercetin. Fasting significantly upregulated the mRNA expression of several drug-metabolizing enzymes in a time-dependent manner and we showed that consuming the low dose of Phoenix dactylifera significantly upregulated the expression of drug-metabolizing enzymes more than the high dose. The results of the histological examinations and relative liver weight showed that fasting and consuming of Phoenix dactylifera did not cause any toxicological alterations in the liver of the mice. It is concluded from this study that fasting and consuming of Phoenix dactylifera upregulated the mRNA expression of major drug-metabolizing enzymes in mouse livers. These findings may explain, at least partly, the variation of drug response during fasting in the month of Ramadan and would direct future clinical studies in optimizing the dosing of pharmacotherapeutic regimen.

Role of the CLOCK protein in liver detoxification.

Whether and how circadian clock proteins regulate drug detoxification are not known. Here, we have assessed the effects of CLOCK (a core circadian clock protein) on drug metabolism and detoxification. Regulation by CLOCK protein of drug-metabolizing enzymes was assessed using Clock knockout (Clock-/- ) mice and Hepa-1c1c7/AML-12 cells. The relative mRNA and protein levels were determined by qPCR and Western blotting respectively. Toxicity and pharmacokinetic experiments were performed with Clock-/- and wild-type mice after intraperitoneal injection of coumarin or cyclophosphamide. Transcriptional gene regulation was investigated using luciferase reporter, mobility shift, and chromatin immunoprecipitation (ChIP) assays. Clock deletion disrupted hepatic diurnal expressions of a number of drug-metabolizing enzymes in mice. In particular, CYP2A4/5 expressions were markedly down-regulated, whereas CYP2B10 was up-regulated. Positive regulation of Cyp2a4/5 and negative regulation of Cyp2b10 by CLOCK were confirmed in Hepa-1c1c7 and AML-12 cells. Based on a combination of luciferase reporter, mobility shift, and ChIP assays, we found that CLOCK activated Cyp2a4/5 transcription via specific binding to E-box elements in promoter region and repressed Cyp2b10 transcription through REV-ERBα/β (two target genes of CLOCK and transcriptional repressors of Cyp2b10). Furthermore, Clock ablation sensitized mice to coumarin toxicity by down-regulating CYP2A4/5-mediated metabolism (a detoxification pathway) and to cyclophosphamide toxicity by up-regulating CYP2B10-mediated metabolism (generating the toxic metabolite 4-hydroxycyclophosphamide). CLOCK protein regulates metabolism by the cytochrome P450 family and drug detoxification. The findings improve our understanding of the crosstalk between circadian clock and drug detoxification.

Effect of MRSA on CYP450: dynamic changes of cytokines, oxidative stress, and drug-metabolizing enzymes in mice infected with MRSA.

BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) is a very damaging and widespread pathogen, which is associated with many diseases and causes serious infections. MRSA infection can modulate the effects of drugs, which may occur through an influence on cytochrome P450 (CYP450), the drug-metabolizing enzyme in the liver. In this study, we evaluated the underlying mechanism of drug failure or poisoning in MRSA infection.Materials and methodsMice were infected with three different doses of MRSA and the changes in CYP450 expression, cytokines, and oxidative stress markers were evaluated.ResultsThe administration of an attack dose of MRSA caused serious symptoms of infection and resulted in a 40% mortality rate in the mice. MRSA induced strong inflammation and oxidative stress in the mice, predominantly caused by significant increases in interleukin (IL)-1β, IL-4, IL-6, macrophage inflammatory protein, glutathione S-transferase (GST), and malondialdehyde, and decreases in oxygen radical absorbance capacity and glutathione levels in the liver. The expression of IL-2, tumor necrosis factor-α, and GST was briefly suppressed, but increased on days 3 and 7. The increased inflammation and oxidative stress further induced a significant decrease in the mRNA levels and activities of CYP450 1A2, 2D22, 2E1, and 3A1 in MRSA-infected mice within the first day of infection.ConclusionThese results show that MRSA infection leads to inflammation and oxidative stress, and reduces the expression levels and activities of drug metabolism enzymes, which decreased drug metabolism in patients infected with MRSA. Therefore, to avoid a drug overdose, the plasma concentration of patients with MRSA infection should be continuously monitored.

Influence of diet supplementation with green tea extract on drug-metabolizing enzymes in a mouse model of monosodium glutamate-induced obesity

Consumption of dietary supplements with green tea extract (GTE) is popular for weight management, but it may be accompanied by various side effects, including interactions with drugs. The aim of the present in vivo study was to evaluate the effect of defined GTE (Polyphenon 60) in three dosage schemes on insulin, leptin and drug-metabolizing enzymes in obese mice. Experimental obesity was induced by repeated s.c. application of monosodium glutamate to newborn mice. Green tea extract was administered in three dosage schemes in chow diet. The plasmatic levels of insulin and leptin were assayed using enzyme-linked immunosorbent assay. Enzyme activities and mRNA expressions of drug-metabolizing enzymes (totally 13) were analyzed in liver and small intestine using spectrophotometric and HPLC assays and RT-PCR, respectively. GTE-treatment decreased insulin and leptin levels. Eleven enzymes were significantly affected by GTE-treatment. Long-term administration of 0.01% GTE caused increase in the activity and mRNA level of cytochrome P450 3A4 (CYP3A4) ortholog in the liver as well as in the small intestine. Interestingly, short-term overdose by GTE (0.1%) had more pronounced effects on enzyme activities and mRNA expressions than long-term overdose. GTE-mediated induction of CYP3A4 ortholog, the main drug-metabolizing enzyme, could result in decreased efficacy of simultaneously or subsequently administered drug in obese individuals.

Effect of defined green tea extract in various dosage schemes on drug-metabolizing enzymes in mice in vivo

Green tea represents a favourite beverage and green tea extracts are popular components of dietary supplements. The aim of present in vivo study was to report on the effect of defined green tea extract (Polyphenon) in various dosage schemes on drug-metabolizing enzymes in mice. The specific activities and expressions of a panel of drug-metabolizing enzymes (totally 16) were tested in liver and small intestine. Nine enzymes were significantly altered by Polyphenon treatment. The intestinal enzymes were more affected than the hepatic ones. The effects were mostly dose-dependent but short-term treatment had more pronounced impact than the long-term administration. Based on the results, normal consumption of green tea seems to be safe but extremely high doses of green tea extracts in dietary supplements could influence drugs metabolism and efficacy.

Anthracosis in a Coptic Mummy

Green tea represents a favourite beverage and green tea extracts are popular components of dietary supplements. The aim of present in vivo study was to report on the effect of defined green tea extract (Polyphenon) in various dosage schemes on drug-metabolizing enzymes in mice. The specific activities and expressions of a panel of drug-metabolizing enzymes (totally 16) were tested in liver and small intestine. Nine enzymes were significantly altered by Polyphenon treatment. The intestinal enzymes were more affected than the hepatic ones. The effects were mostly dose-dependent but short-term treatment had more pronounced impact than the long-term administration. Based on the results, normal consumption of green tea seems to be safe but extremely high doses of green tea extracts in dietary supplements could influence drugs metabolism and efficacy.

Differences in metabolite burden of di(2-ethylhexyl)phthalate in pregnant and postpartum dams and their offspring in relation to drug-metabolizing enzymes in mice

Di(2-ethylhexyl)phthalate (DEHP) induced adverse effects on mice offspring, and the metabolite mono(2-ethylhexyl)phthalate (MEHP) may be essential to determine the toxicity. In this experiment, we measured liver MEHP levels and the factors determining the metabolism, two enzyme activities [lipase and uridine 5'-diphosphate-glucuronosyltransferase (UGT)] or expression of cytochrome P450 4A14 (CYP4A14) in dams (on gestational day 18 and postnatal day 2) and their offspring. MEHP concentrations in the liver from pregnant dams were 1.5 times higher than those of postpartum dams at exposure to 0.05% DEHP. Accordingly, MEHP concentrations were 1.7 times higher in fetuses than in pups at the dose. Interestingly, lipase activity was 1.8-fold higher in pregnant dams than postpartum ones, but no such difference was noted in the activity between fetuses and pups. UGT activity was also 1.5-fold higher in pregnant dams than postpartum ones, whereas the activity in the fetuses was 1/2 that of pups. No difference was noted in CYP4A14 levels between pregnant and postpartum mice, whereas the levels in the fetuses were <1/10 those of pups. DEHP exposure did not influence lipase activity, whereas it slightly enhanced UGT activity and exclusively increased CYP4A14 levels in pregnant and/or postpartum dams. Taken together, the higher MEHP levels in pregnant dams than postpartum ones may be primarily due to higher lipase activities in pregnant dams, which may closely reflect those in fetuses and pups.

Sho-saiko-to and Saiko-keisi-to, the traditional Chinese and Japanese herbal medicines, altered hepatic drug-metabolizing enzymes in mice and rats when administered orally for a long time

As the consumption of herbal remedies has increased, the opportunity that such herbal medicines are co-administered with other drugs has also risen gradually and we are, therefore, very much concerned about herb-drug interactions. We examined the effects of pre-administration of Kampo medicines (Sho-saiko-to, Saiko-keishi-to, Shigyaku-san and Dai-saiko-to) on the pentobarbital-induced sleeping time in mice and rats, to clarify the possibility that they could affect the drug-metabolizing enzymes. The administration of Sho-saiko-to and Saiko-keishi-to for 4 weeks significantly shortened the pentobarbital-induced sleeping time in mice and the administration of Sho-saiko-to for 2 weeks significantly reduced the sleeping time in rats. Furthermore, we tried to identify the molecular species of rat cytochrome P450s (CYPs) affected by Sho-saiko-to and Saiko-keishi-to by competitive RT-PCR. The oral administration of Sho-saiko-to for 2 weeks upregulated the mRNA expression of CYP2B, CYP3A1, CYP2E1 and CYP4A1 in rats. The treatment with Saiko-keishi-to for 2 weeks also up-regulated the mRNA expression of CYP2B, CYP3A1 and CYP4A1. Sho-saiko-to and Saiko-keishi-to may potentially influence the drug-metabolizing enzymes in man, and would thus require much attention when used in the clinical situation.

Mechanism of Inhibitory Effects of Cannabidiol and Cannabidiol Hydroxy-quinone on the Hepatic Microsomal Drug-Metabolizing Enzymes in Mice (Proceedings of the 23rd Symposium on Toxicology and Environmental Health)

Mechanism of Inhibitory Effects of Cannabidiol and Cannabidiol Hydroxy-quinone on the Hepatic Microsomal Drug-Metabolizing Enzymes in Mice (Proceedings of the 23rd Symposium on Toxicology and Environmental Health)

Effects of co-administration of butylated hydroxytoluene, butylated hydroxyanisole and flavonoids on the activation of mutagens and drug-metabolizing enzymes in mice

Effects of co-administration of food additives and naturally occurring food components were studied on the activation of mutagens. Male mice (ddY) were given diets containing butylated hydroxytoluene (BHT) or butylated hydroxyanisole (BHA) and flavone or flavanone (2,3-dihydroflavone) for two weeks and the ability of hepatic microsomes to activate aflatoxin B 1, benzo[a]pyrene and N-nitrosodimethylamine was determined by the mutagenicity test. Co-administration of an antioxidant (0.1% BHT or 0.2% BHA in diet) and a flavonoid (0.1% flavone or 0.1% flavanone) resulted in additive effects on the activation of aflatoxin B 1 and benzo[a]pyrene, while the activation of N-nitrosodimethylamine was not elevated significantly by the co-administration. To understand the mechanism for the additive effects, induction of specific isozymes of cytochrome P450 involved in the activation of the mutagens was studied. Co-administration of BHT (0.1%) and flavone (0.1%) increased markedly the levels of proteins and the activities of the enzymes related to the isozymes of CYP2A and CYP2B, while co-administration of BHA (0.2%) and flavanone (0.1%) elevated those related to CYP1A. Further, the activation of aflatoxin B 1 and benzo[a]pyrene in hepatic microsomes was inhibited by the antibodies against these isozymes, which suggested that the enhanced activation of the mutagens by the co-administration might be mediated by the induction of these isozymes.

Effect of Diclofenac and Naproxen on Drug-Metabolizing Enzymes in Mice.

The effect of non-steroidal anti-inflammatory drugs (NSAIDs) diclofenac and naproxen on xenobiotic-metabolizing enzymes was studied in male Swiss mice given the drugs in their diet. Diclofenac at levels of 25, 75, and 375ppm, and naproxen at 150, 500, and 1, 500ppm, were given for a period of 4 weeks. Control animals consumed a similar diet deprived of the test NSAIDs. Feeding of NSAIDs did not affect the activity of arylhydrocarbon hydroxylase, whereas the level of cytochrome P-450 (P-450) was significantly decreased in liver and lungs of the animals. The maximum decline in content of the enzyme was found at the largest dose of NSAIDs. On the other hand, the activity of glutathione-S-transferase (GST) was significantly increased in the two organs by both drugs. However, hepatic activity of the enzyme after induction by 375ppm diclofenac was almost 1.37 fold greater in comparison to that after induction by 1, 500ppm naproxen. In lungs, this ratio was found to be 1.76. Like GST, reduced glutathione (GSH) levels in the liver and lungs of the animals were also significantly increased. The maximum increase in GSH in lungs elicited by the two NSAIDs was similar. The results of this study indicate that diclofenac might prove to be a better chemopreventive agent against xenobiotics because of the higher induction of GST activity by it.

Comparison of effects of xenobiotics on extrahepatic and hepatic microsomal drug-metabolizing enzymes in mice

The content of microsomal protein is the same in both kidneys and small intestine, corresponding to 57% of the control value expressed as 100% in the untreated liver. The contents of P450 and cytochrome b 5, and the activity of NADPH-cytochrome c reductase in the kidney were higher than those in the small intestine, which were 17%, 22% and 41% of controls, respectively, in the former and 5%, 11% and 22% of controls in the latter. As compared with similar measurements made in the liver, the activities of substrate-metabolizing enzymes in these extrahepatic organs were very low. The activities of renal aniline hydroxylase, aminopyrine N-demethylase, 7-ethoxycoumarin O-deethylase, 7-methoxycoumarin O-demethylase and benzo(a)pyrene hydroxylase were 6%, 5%, 3%, 0.6% and 0.2% of controls, respectively. The activities of these enzymes in the small intestine were lower than those in the kidney or below the limits of detection. These results suggested that isoforms or their contents of P450 responsible for these substrate biotransformations are different among liver, kidneys and small intestine. Meantime, this study showed similar significant inductions by phenobarbital and rifampin of small intestinal and hepatic microsomal drug-metabolizing enzymes. In contrast, neither phenobarbital nor rifampin was capable of increasing renal microsomal enzymes, with the exception of benzo(a)pyrene hydroxylase which was induced by rifampin. These findings indicated that both liver and small intestine, but not kidneys contain the same phenobarbital- and rifampin-inducible P450 isoforms, cytochrome b 5 and NADPH-cytochrome c reductase. In addition, CCl 4 could be bioactivated by CYP2E1 to free radicals in the kidney which caused destruction of microsomal enzymes. In mice pretreated with phenobarbital, CCl 4 also attenuated the increase in content of P450 in the small intestine, which appeared to be a result of induction by phenobarbital of CYP2E1.

Impact of Quercetin Consumption on Phase-I and Phase-II Drug-Metabolizing Enzymes in Mice.

In the present study Swiss NMRI mice were fed quercetin, a naturally-occurring dietary polyphenolic flavonoid, through their drinking water at dose levels of 0, 1, 3, and 9μg/ml for 8 weeks. There was no change in the hepatic and pulmonary levels of arylhydrocarbon hydroxylase, cytochrome P-450, cytochrome b5, cytochrome c-reductase, or UDP-glucuronyltransferase due to quercetin feeding. However, hepatic activity of glutathione-S-transferase was significantly increased at 3 and 9μg/ml dose levels; and that of the pulmonary enzyme, at 9μg/ml dose. Levels of reduced glutathione were significantly elevated in liver and lungs. These increases in glutathione-S-transferase and reduced glutathione may protect the liver and lungs from the carcinogenic insult of chemicals through the detoxification process.

Effects of acetone administration on drug-metabolizing enzymes in mice: presence of a high-affinity diethylnitrosamine de-ethylase

Treatment of CD1 mice with acetone raised activities of hepatic microsomal p-nitrophenol hydroxylase, ethoxycoumarin de-ethylase, acetone hydroxylase and diethylnitrosamine de-ethylase (DENd) several-fold. P-450IIE1-linked acetone hydroxylase showed the highest inducibility. In microsomes from acetone-pretreated mice the cytochrome b5 and P-450 content was nearly doubled and their electrophoretic profile showed induction of a protein of Mr 53 000, probably P-450IIE1. Liver phase II enzymes were not affected by acetone treatment. Kinetic analyses of DENd were performed in control or acetone-induced microsomes and K m and V max were determined. Two distinctly apparent K m values (0.56 and 20.3 mM) were observed for DENd of control microsomes and at least 3 apparent K m values (0.05, 0.51, 8.4 mM) were observed in acetone-induced microsomes. Thus, acetone administration to mice induces a high-affinity form of DENd which can be important in vivo at low diethylnitrosamine (DEN) exposure as this enzyme functions when DEN concentration is below 0.1 mM.

Effects of m-dichlorobenzene and its sulfur-containing metabolites on hepatic drug-metabolizing enzymes in mice.

Sulfur-containing metabolites, 2, 4-dichlorophenyl methyl sulfoxide, 2, 4-dichlorophenyl methyl sulfone (2, 4-DCPSO2CH3), 3, 5-dichlorophenyl methyl sulfoxide and 3, 5-dichlorophenyl methyl sulfone (3, 5-DCPSO2CH3) were all found in the urine of both male and female mice given orally a 200 mg/kg dose of m-dichlorobenzene (m-DCB). m-DCB (200 mg/kg) given to mice of both sexes by either oral or intraperitoneal (i.p.) route increased the activities of aminopyrine N-demethylase (AD) and aniline hydroxylase, and the content of cytochrome P-450 in the liver microsomes. 3, 5-DCPSO2CH3 (100μmol/kg, i.p.) induced markedly the enzyme system in mice of both sexes. On the other hand, 2, 4-DCPSO2CH3 (100 μmol/kg, i.p.) decreased significantly the AD activity in the males and the cytochrome b5 content in the females. An i.p. administration of m-DCB, 2, 4-DCPSO2CH3 or 3, 5-DCPSO2CH3 also caused a marked increase in epoxide hydrolase activity in the livers of the male and female mice, except that 2, 4-DCPSO2CH3 had no effect on the enzyme activity in the females. Thus, the differences in the effects of 2, 4- and 3, 5-DCPSO2CH3 on the enzyme system were demonstrated and the sex differences in the effects of the sulfones were also found in mice.

In vivo effects of tetrahydrocannabinols and their eight monooxygenated metabolites of the hepatic microsomal drug-metabolizing enzyme systems of mice.

In vivo effects of tetrahydrocannabinols (THCs) and their eight monooxygenated metabolites on the hepatic microsomal drug-metabolizing enzymes in mice were studied. delta 8-THC and its metabolites (7 alpha-hydroxy-, 7 beta-hydroxy- and 7-oxo-delta 8-THC, and 8 alpha, 9 alpha- and 8 beta, 9 beta-epoxyhexahydrocannabinol) tended to increase the enzyme contents or activities except for 7 beta-hydroxy-delta 8-THC which affected the microsomal enzymes in a different manner between the single and subchronic treatments. Single administration (5 mg/kg, i.v.) of 7-oxo-delta 8-THC, 8 alpha, 9 alpha- and 8 beta, 9 beta-epoxyhexahydrocannabinol led to the significant increase in hepatic microsomal p-nitroanisole O-demethylase and aniline hydroxylase activities accompanying a significant increase in cytochrome P-450 content in hepatic microsomes. The same results were obtained with subchronic treatment of mice with these metabolites (5 mg/kg/d, i.v. for 7 d), although the effect of 8 beta, 9 beta-epoxyhexahydrocannabinol on cytochrome P-450 was not statistically significant. 7 beta-Hydroxy-delta 8-THC significantly increased nicotinamide adenine dinucleotide phosphate (NADPH)-cytochrome c reductase and aniline hydroxylase activities by single administration, while the metabolite significantly decreased the contents of cytochrome b5 and P-450 and p-nitrophenol uridine diphosphate-glucuronyltransferase activity by the subchronic treatment. In contrast, delta 9-THC and its metabolites (8 alpha-hydroxy-, 8 beta-hydroxy- and 8-oxo-delta 9-THC) did not significantly affect the microsomal enzymes by both treatments except that the single administration of 8 alpha-hydroxy-delta 9-THC and the subchronic treatment of delta 9-THC significantly decreased NADPH-cytochrome c reductase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of Dietary β-Carotene on Hepatic Drug-Metabolizing Enzymes in Mice

The effects of dietary supplements of β-carotene (20-500mg per kg diet) on hepatic microsomal drug-metabolizing enzyme activities were studied in mice. Supplementation for 14 days resulted in marked reductions in the concentrations of cytochrome P-450 and biphenyl 4-hydroxylase. The antipyrine N-demethylase and p-nitroanisol O-demethylase activities, however, were unchanged. Also apparently unchanged were the hepatic concentrations of microsomal protein, lipid peroxides, and superoxide dismutase. Supplemental β-carotene was weakly protective against the acute toxic effects of an injection of 1, 2-dimethylhydrazine (DMH), as indicated by a lowered mortality. This anti-carcinogenic action of β-carotene, including a protection against DMH-induced colon carcinogenesis, suggests an alteration by this carotenoid in the metabolism of carcinogens by the liver.

1,4-Bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP) and related compounds as inducers of hepatic monooxygenases: Structure-activity effects

1,4-Bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP) resembles phenobarbital (PB) in its mode of induction of the hepatic drug-metabolizing enzymes in mice. The structural features of this molecule include: a linear tricyclic aromatic ether ring system, an internal 1,4-disubstituted benzene ring and two 3,5-dichloropyridyloxy substituents. Ten analogs of TCPOBOP have been synthesized and their activities as microsomal enzyme inducers evaluated. Dose-response induction of mice hepatic microsomal cytochrome P-450, aldrin epoxidase and dimethylaminoantipyrine N-demethylase gave ed 50 values for TCPOBOP and five homologs. The results illustrate that changes in the structure of the pyridyloxy ring markedly affect enzyme induction activity. The order of activity for the substituents was 3,5-dibromopyridyloxy ≈ 3,5-dichloropyridyloxy > 5-bromopyridyloxy ≈ 5-chloropyridyloxy > 3-chloropyridyloxy > pyridyloxy. In addition, the effects of altered substitution pattern of the benzene ring and structural alterations of the internal ring moiety were evaluated by measuring hepatic microsomal coumarin hydroxylase activity. The results confirm the microsomal monooxygenase enzyme induction activity of TCPOBOP, and the observed structure-dependent potencies of several related homologs support a receptor-mediated mechanism of action for the process.

Potentiation of the teratogenic effects and altered disposition of diphenylhydantoin in mice fed a purified diet

The effect of a standardized purified diet (AIN-76) on the teratogenic response to diphenylhydantoin (DPH) was studied in mice. Mice were fed either the purified diet or Purina Rodent Laboratory Chow for 2–4 weeks prior to mating, and were treated with either saline or 50 mg/kg of DPH on Days 12, 13, and 14 of gestation (copulatory plug = Day 0). The teratogenic response to DPH was found to be markedly potentiated in mice fed the purified diet (75% cleft palate) as compared to mice fed rodent chow (21% cleft palate). The potentiated teratogenic response to DPH correlated with markedly higher plasma DPH levels in pregnant mice fed the purified diet, indicating that the disposition of DPH was impaired. These effects were attributed to a decreased basal level of drug-metabolizing enzymes in mice fed the purified diet, as indicated by markedly prolonged hexobarbital sleeping times. Modifications of the purified diet, which included the replacement of soluble carbohydrate (50% sucrose) in the purified diet with either cornstarch or casein, did not alter the high incidence of cleft palate. A reduction in the incidence of cleft palate was observed, however, when corn oil in the purified diet was replaced with linseed oil. The replacement of corn oil with linseed oil in the purified diet also restored the hexobarbital sleeping times to those observed in mice fed rodent chow. It is concluded that mice fed purified diets have decreased basal levels of drug-metabolizing activity that alter the disposition of DPH and, as a consequence, potentiate its teratogenic effects.

Depression of Hepatic Microsomal Enzyme Systems by Lentinan in Mice

Studies were performed to determine the effects of an immunopotentiating agent, lentinan, on the hepatic drug-metabolizing enzymes in mice. Lentinan was injected twice a day for two days, and the enzyme activities were determined 12 hr after the last injection of lentinan. A lentinan dose of over 0.25 mg/kg was required to cause a significant decrease (20–40%) in the hepatic microsomal aminopyrine N-demethylase and aniline hydroxylase activities. The loss of drug-metabolizing activity by the treatment with lentinan agreed with the loss of cytochrome P-450 content in many cases. Strain and substrate differences concerning the effect of lentinan on the metabolism of drug were also observed. That is to say, the loss of cytochrome P-450 content by the treatment with lentinan was observed in the ddY, C57BL/6 and BDF1 strain mice, but was not observed in the DBA/2, C3H/He and C57BL/10 strain mice. The decrease in the activities of 7-ethoxycoumarin O-deethylase and biphenyl 2-hydroxylase by the treatment with lentinan was considerably less than that of aminopyrine N-demethylase and aniline hydroxylase in ddY mice.