Microbial contamination of tattoo and permanent makeup inks marketed in the US: a follow-up study.

In a 2018 survey, U.S. Food and Drug Administration (FDA) identified microbial contamination in 42 (49%) of 85 unopened tattoo and permanent makeup (PMU) inks purchased from 13 manufacturers in the US between November 2015 and April 2016. To confirm the results of our previous survey, we evaluated the level of microbial contamination in an additional 27 samples from 10 manufacturers from September 2017 to December 2017, including 21 unopened tattoo and PMU inks which were selected based on our previous survey results and 6 ink diluents that were not previously analysed. Aerobic plate count and enrichment culture methods from the FDA's Bacteriological Analytical Manual revealed 11 (52%) out of 21 inks, from six manufacturers, were contaminated with micro-organisms, with contamination levels up to 3·6 × 108  CFU per gram, consistent with our previous survey results. We identified 25 bacterial strains belonging to nine genera and 19 species. Strains of Bacillus sp. (11 strains, 44%) were dominant, followed by Paenibacillus sp. (5 strains, 20%). Clinically relevant strains, such as Kocuria rhizophila and Oligella ureolytica, were also identified, as similar to the findings in our previous survey. No microbial contamination was detected in any of the six ink diluents.

FDA 2014 survey of eye area cosmetics for microbiological safety.

In an attempt to assess cosmetics containing 'nontraditional' preservatives, 93 eye area cosmetic products were selected based on labelled or marketed claims that these products were 'green', 'natural', 'paraben-free', 'preservative-free' or contained nontraditional preservatives (e.g. botanical extracts). Products were analysed for water activity, pH and microbiological content, which included enumeration of aerobic micro-organisms, detection of microbial growth after a 7-day enrichment and identification of microbial isolates. The survey found that 60% (56/93) of the eye area cosmetics were free of microbiological growth under test conditions, 32% (30/93) showed the presence of micro-organisms at low levels (<100 CFU per ml or g) and 8% (7/93) showed microbiological growth at higher levels (> 100 CFU per ml or g). Gram-positive bacteria such as Bacillus and Staphylococcus were the dominant genera identified in these cosmetic products, whereas Gram-negative species were relatively uncommon. The survey found a positive association between lower water activity cosmetics and the presence of micro-organisms in these products. Similarly, colour cosmetics were more likely to contain micro-organisms than noncolour cosmetics. The most represented micro-organisms in the survey were from genus Bacillus, suggesting that the natural raw materials are the likely source of observed microbial loads. SIGNIFICANCE AND IMPACT OF THE STUDY: In the United States, cosmetic products are regulated postmarket; therefore, surveillance programmes are one of FDA's most important tools for monitoring microbiological safety of cosmetics. 'Traditional' preservatives, such as parabens and formaldehyde releasers, are perceived unfavourably by some consumers, resulting in cosmetic manufacturers increasingly using 'nontraditional' preservatives. FDA conducted an analytical survey of eye area cosmetics that claimed to be free of traditional preservatives and determined microbiological loads in tested products. This study explores the association of microbial loads with the physical and chemical characteristics of the cosmetic products, and points to the limits of preservative activity in cosmetics.

Microbiological survey of commercial tattoo and permanent makeup inks available in the United States.

AIMS: Tattooing and use of permanent makeup (PMU) has dramatically increased over the last decade, with a concomitant increase in ink-related infections. The aim of this study was to determine whether micro-organisms are present, and if so, the number and their identification in the commercial tattoo and PMU inks available in the United States. METHODS AND RESULTS: We surveyed 85 unopened tattoo and PMU inks, purchased from 13 companies. We incubated 100 µl of ink samples on trypticase soy agar plates for bacterial growth, 7H10 Middlebrook medium for mycobacterial growth, and Sabouraud dextrose medium for fungal growth. In total, 42 inks were contaminated with micro-organisms (49%). Thirty-three inks were contaminated with bacteria, 2 inks with fungi, and 7 inks had both bacterial and fungal growth. Mycobacteria were not detected in any of the examined tattoo and PMU inks. In 26 inks, microbial concentrations ranged between 101 and 103 CFU per ml, but higher counts (>103 CFU per ml) were recorded in 16 inks. We identified 83 bacteria by their 16S rDNA sequences, including 20 genera and 49 species. Strains of Bacillus spp. (53%) were dominant, followed by Lysinibacillus fusiformis (7%) and Pseudomonas aeruginosa (5%). Thirty-four (41%) possibly clinically relevant strains were identified, including P. aeruginosa, Dermacoccus barathri and Roseomonas mucosa, some of which have been previously reported to be associated with human skin infections. CONCLUSIONS: The results indicate that commercial tattoo and PMU inks on the US market surveyed in this study contain a wide range of micro-organisms, including pathogenic bacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: Microbial contaminants in tattoo and PMU inks are an emerging safety concern for public health. This study provides evidence that microbial contamination of tattoo and PMU inks available in the United States is more common than previously thought and highlights the importance of monitoring these products for potentially pathogenic micro-organisms.

Tissue distribution and histopathological effects of titanium dioxide nanoparticles after intravenous or subcutaneous injection in mice.

Nanoparticles can be formed following degradation of medical devices such as orthopedic implants. To evaluate the safety of titanium alloy orthopedic materials, data are needed on the long-term distribution and tissue effects of injected titanium nanoparticles in experimental animals. In this study, we evaluated the tissue distribution and histopathological effects of titanium dioxide (TiO(2)) nanoparticles (approximately 120 nm diameter) in mice after intravenous (i.v.; 56 or 560 mg kg(-1) per mouse) or subcutaneous (s.c.; 560 or 5600 mg kg(-1) per mouse) injection on two consecutive days. Animals were examined 1 and 3 days, and 2, 4, 12 and 26 weeks after the final injection. When examined by light microscopy, particle agglomerates identified as TiO(2) were observed mainly in the major filtration organs - liver, lung and spleen - following i.v. injection. Particles were still observed 26 weeks after injection, indicating that tissue clearance is limited. In addition, redistribution within the histological micro-compartments of organs, especially in the spleen, was noted. Following s.c. injection, the largest particle agglomerates were found mainly in the draining inguinal lymph node, and to a lesser extent, the liver, spleen and lung. With the exception of a foreign body response at the site of s.c. injection and the appearance of an increased number of macrophages in the lung and liver, there was no histopathological evidence of tissue damage observed in any tissue at any time point.

The state of nano-sized titanium dioxide (TiO2) may affect sunscreen performance.

In the past several years, there has been a trend in the sunscreen/cosmetics industry to replace micron-sized titanium dioxide (TiO(2)) particles with nanoscale materials. The increased use of nanoscale TiO(2) has resulted in questions about these and other nanoproducts. This study examines the effects of using nanoscale TiO(2) on ultraviolet (UV) attenuation in simple to complex sunscreen formulations. UV light attenuation, product stability, and potential damage to the skin barrier were examined with both nanoscale and microscale TiO(2) particles. Results indicate that none of the formulations decreased the barrier function of the skin and the best UV attenuation occurs when the TiO(2) particles are stabilized with a coating and evenly distributed such as with non-agglomerated coated nanoscale materials. This indicates that nanoscale TiO(2) may have better efficacy while lacking toxicity.

Age-related differences in susceptibility to cisplatin-induced renal toxicity.

Limited experimental models exist to assess drug toxicity in pediatric populations. We recently reported how a multi-age rat model could be used for pre-clinical studies of comparative drug toxicity in pediatric populations. The objective of this study was to expand the utility of this animal model, which previously demonstrated an age-dependent sensitivity to the classic nephrotoxic compound, gentamicin, to another nephrotoxicant, namely cisplatin (Cis). Sprague-Dawley rats (10, 25, 40 and 80 days old) were injected with a single dose of Cis (0, 1, 3 or 6 mg kg(-1) i.p.). Urine samples were collected prior and up to 72 h after treatment in animals that were >or= 25 days old. Several serum, urinary and 'omic' injury biomarkers as well as renal histopathology lesions were evaluated. Statistically significant changes were noted with different injury biomarkers in different age groups. The order of age-related Cis-induced nephrotoxicity was different than our previous study with gentamicin: 80 > 40 > 10 > 25 day-old vs 10 >or= 80 > 40 > 25-day-old rats, respectively. The increased levels of kidney injury molecule-1 (Kim-1: urinary protein/tissue mRNA) provided evidence of early Cis-induced nephrotoxicity in the most sensitive age group (80 days old). Levels of Kim-1 tissue mRNA and urinary protein were significantly correlated to each other and to the severity of renal histopathology lesions. These data indicate that the multi-age rat model can be used to demonstrate different age-related sensitivities to renal injury using mechanistically distinct nephrotoxicants, which is reflected in measurements of a variety of metabolite, gene transcript and protein biomarkers.

A modern view of excipient effects on bioequivalence: case study of sorbitol.

PURPOSE: To examine the effect of common excipients such as sugars (sorbitol versus sucrose) on bioequivalence between pharmaceutical formulations, using ranitidine and metoprolol as model drugs. METHODS: Two single-dose, replicated, crossover studies were first conducted in healthy volunteers (N=20 each) to compare the effect of 5 Gm of sorbitol and sucrose on bioequivalence of 150 mg ranitidine or 50 mg metoprolol in aqueous solution, followed by a single-dose, nonreplicated, crossover study (N=24) to determine the threshold of sorbitol effect on bioequivalence of 150 mg ranitidine in solution. RESULTS: Ranitidine Cmax and AUC0-infinity were decreased by approximately 50% and 45%, respectively, in the presence of sorbitol versus sucrose. Similarly, sorbitol reduced metoprolol Cmax by 23% but had no significant effect on AUC0-infinity. An appreciable subject-by-formulation interaction was found for ranitidine Cmax and AUC0-infinity, as well as metoprolol Cmax. Sorbitol decreased the systemic exposure of ranitidine in a dose-dependent manner and affected bioequivalence at a level of 1.25 Gm or greater. CONCLUSIONS: As exemplified by sorbitol, some common excipients have unexpected effect on bioavailability/bioequivalence, depending on the pharmacokinetic characteristics of the drug, as well as the type and amount of the excipient present in the formulation. More research is warranted to examine other 'common' excipients that may have unintended influence on bioavailability/bioequivalence.

Formation of DNA adducts of the food-derived mutagen 2-amino-9H-pyrido-[2,3-b]indole (A(alpha)C) and bioassay of mammary gland carcinogenicity in Sprague-Dawley rats.

2-amino-9H-pyrido[2,3-b]indole (AalphaC) is a heterocyclic amine found at relatively high concentrations in barbecued or grilled meats. In the current study, the mammary gland carcinogenicity of AalphaC was examined in female Sprague-Dawley rats given 10 doses of AalphaC (75 mg/kg, orally, once per day starting at 43 days of age) and placed on a defined high-fat diet (23.5% corn oil), a strong promotional factor for rat mammary gland carcinogenesis. Within 1 year, one out of 20 rats dosed with AalphaC developed a tubulopapillary carcinoma, indicating that the bioassay was largely negative. As DNA adduct formation is considered to play a role in carcinogenesis, AalphaC-DNA adduct levels were measured in the mammary gland and other tissues by the 32P-postlabelling method. Under intensification conditions, one major adduct and up to three minor adducts were detected in isolated mammary gland epithelial cells and other tissues (liver, stomach, small intestine, colon and kidney) of AalphaC-treated rats; the adduct patterns were similar in all tissues examined. The major adduct, comprising 60-100% of total DNA adduct levels in tissues, was chromatographically identical to the principal adduct found in 3'-dGp-AalphaC (synthesized by reacting 3'-phospho-2'-deoxyguanosine (3'-dGp) with N-acetoxy-AalphaC). Of the tissues examined, the highest AalphaC-DNA adduct levels were found in the liver. In male rats given a single dose of AalphaC (75 mg/kg, orally, 3 hr prior to necropsy), no AalphaC-DNA adducts were detected in extrahepatic tissues. In female rats given a single dose or 12 daily doses of AalphaC, hepatic DNA adduct levels were at least 12-13-fold higher than those in any other tissue. Mean total AalphaC-DNA adduct levels in mammary gland epithelial cells and liver from female rats given multiple doses of AalphaC were 3.5 and 50.7 (RAL x 10(7)), respectively. Although factors in addition to DNA adduct formation are likely to play a role in mammary gland carcinogenesis, the results suggest that the weak mammary gland carcinogenicity of AalphaC may in part be associated with low AalphaC-DNA adduct levels in the mammary gland epithelium.

Metabolism of food-derived heterocyclic amines in nonhuman primates.

During the cooking of meats, several highly mutagenic heterocyclic amines (HCAs) are produced. Three HCAs, IQ, MeIQx, and PhIP have been under study for carcinogenicity in cynomolgus monkeys, and to date, IQ has been shown to be a potent hepatocarcinogen. Concomitantly, the metabolic processing of these HCAs has been examined. Metabolism studies show that the potent hepatocarcinogenicity of IQ is associated with the in vivo metabolic activation of IQ via N-hydroxylation and the formation of DNA adducts. In monkeys undergoing carcinogen bioassay with IQ, N-hydroxylation was confirmed by the presence of the N-hydroxy-N-glucuronide conjugate of IQ in urine. The N-hydroxylation of IQ appears to be carried out largely by hepatic CYP3A4 and/or CYP2C9/10, and not by CYP1A2, an isoform not expressed in liver of this species. Notably MeIQx is poorly activated in cynomolgus monkeys and lacks the potency of IQ to induce hepatocellular carcinoma after a 5-year dosing period. The poor activation of MeIQx appears to be due to the lack of constitutive expression of CYP1A2 and an inability of other cytochromes P450, such as CYP3A4 and CYP2C9/10, to N-hydroxylate the quinoxalines. MeIQx is detoxified in monkeys largely by conjugation with glucuronide at the N-1 position. Although the carcinogenicity of PhIP is not yet known, the metabolic data suggest that PhIP will be carcinogenic in this species. PhIP is metabolically activated in vivo in monkeys by N-hydroxylation, as discerned by the presence of the N-hydroxy-N-glucuronide conjugate in urine, bile, and plasma. PhIP also produces DNA adducts that are widely distributed in tissues. The results from these studies support the importance of N-hydroxylation in the carcinogenicity of HCAs in nonhuman primates and by analogy, the importance of this metabolic activation step in the possible carcinogenicity of dietary HCAs in humans.

Induction of the male-specific cytochrome P450 3A2 in female rats by phenytoin.

We previously reported that administration of dexamethasone (DEX) and other selected pharmacological agents to rats resulted in a profound increase in hepatic cytochrome P450 3A1 in both sexes, but male constitutive P450 3A2 was modestly increased (4-fold) in adult males and not detected in either treated or untreated females (Cooper et al., Arch. Biochem. Biophys. 301, 345, 1993). Using a more sensitive Western blot stain, we have now detected in females low but significant induction of P450 3A2 by DEX. Of 10 compounds tested, DEX was the most effective inducer of P450 3A1 in either sex and of P450 3A2 in males. Unexpectedly, the antiepileptic, phenytoin, was the most potent inducer of P450 3A2 in females, resulting in levels up to 30% of those seen in untreated males. Even more striking, phenytoin differentially induces the male-specific P450 3A2 with barely detectable increases in P450 3A1 in either sex. By comparison, when administered to female rats, the other active P450 3A inducers preferentially induce P450 3A1 compared to 3A2 by ratios ranging from 3- to 400-fold. Another male-specific isozyme, P450 2C11, was induced in females by both DEX and phenytoin, but DEX was much more effective than phenytoin. These results suggest that the masculinization of expression of these two sexually dimorphic isozymes of cytochrome P450 may occur by different mechanisms, and that phenytoin is atypical of the other nine compounds we tested. Moreover, of the known inducers of the "steroid inducible" 3A family, phenytoin is unique in its ability to differentially induce P450 3A2 compared to P450 3A1, particularly in the female rat. Also, administration of phenytoin to female rats gave rise to P450 3A2 levels that could be divided into two distinct classes of high and low levels of P450 3A2. Should this prove to be a genetic polymorphism, it could be very useful in studies on the mechanism of P450 3A2 induction.

N-acetyltransferase expression and metabolic activation of the food-derived heterocyclic amines in the human mammary gland.

The heterocyclic amines (HCAs) found in cooked meat are procarcinogens that are metabolically activated by N-hydroxylation followed by O-acetylation by the N-acetyltransferases NAT1 and NAT2. Despite the importance of metabolic activation in HCA carcinogenicity and the finding that several HCAs are rodent mammary gland carcinogens, nothing was known about O-acetylation activity in the human mammary gland. The current study examines the expression and catalytic activity of NAT toward the N-hydroxy-HCAs 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine (N-hydroxy-PhIP) and 2-hydroxy-amino-3-methylimidazo[4,5-f]quinoline (N-hydroxy-IQ) in the human mammary gland. Mammary gland cytosol from 10 women and lysates from a primary culture of human mammary epithelial cells metabolically activated 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine and 2-hydroxyamino-3-methylimidazo[4,5-f]quinoline by NAT-mediated 0-acetyltransferase, as measured by the acetyl CoA-enhanced binding of the N-hydroxylamines to calf thymus DNA in vitro. N-acetylation of p-aminosalicylic, an activity specific to NAT1, but not N-acetylation of sulfamethazine, an activity specific to NAT2, was detected in the mammary gland cytosols and human mammary epithelial cell lysates. Immunohistochemical analysis of human mammary gland sections showed positive staining for NAT1 protein in the epithelial cells lining the mammary gland ducts. Reverse transcription-PCR analysis showed that mRNA transcripts for both NAT1 and NAT2 were present in human mammary gland; however, no NAT2 catalytic activity was detectable. Our data demonstrate for the first time that the human mammary gland is catalytically active toward the metabolic activation of HCA food mutagens, and that this activity is most likely contributed by NAT1 expressed in the ductular epithelial cells of the mammary gland.

Cytochromes P450 in cynomolgus monkeys mutagenically activate 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) but not 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx).

The promutagenic and procarcinogenic heterocyclic amines (HAs) found in cooked meats are N-hydroxylated by microsomal cytochrome P450 enzymes as the first step in their metabolic activation. In cynomolgus monkeys, one of the HAs, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), has been shown to be a potent hepatocarcinogen. However, the structurally similar HA 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) lacks this potency to induce hepatocellular carcinoma in monkeys. Liver microsomes from cynomolgus monkeys show a striking substrate specificity for the metabolic activation of IQ and MeIQx, the former being a far better substrate for N-hydroxylation. Western blot analysis showed that cynomolgus monkey hepatic microsomes constitutively express P450s immunologically related to the human CYP3A, CYP2C, and low levels of CYP1A1. For comparison, Western blot analysis of rat, human and patas monkey microsomes was also carried out. Treatment of cynomolgus monkeys with rifampicin induced hepatic cytochromes P450 related to human CYP3A4 and CYP2C9/10 without inducing CYP1A1 or CYP1A2. Immunoblot analysis also showed that chronic exposure of cynomolgus monkeys to IQ induced hepatic microsomal cytochrome CYP1A1 and CYP1A2, similarly but lesser in magnitude to that observed with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCCD) induction. Using the Ames Salmonella mutagenicity assay, we examined the effect of the inducers on the mutagenic activation (i.e. N-hydroxylation) of IQ and MeIQx by cynomolgus monkey hepatic microsomes. We also examined the mutagenic activation of these HAs by rat, human and patas monkey liver microsomes. Microsomes from cynomolgus monkeys treated with rifampicin showed a 3-fold increase in the mutagenic activation of IQ but showed no increase in the mutagenic activation of MeIQx. Since cytochromes P4503A and/or P4502C are constitutively expressed in cynomolgus monkey hepatic microsomes, and upon induction with rifampicin are associated with an increased metabolic activation of IQ but not MeIQx, it appears that CYP3A and/or CYP2C are the isoform(s) showing the selective substrate specificity in the metabolic activation of IQ over MeIQx. Treatment of monkeys with TCDD significantly increased the mutagenic activation of both IQ and MeIQx, concomitant with an induction of CYP1A isozymes. Thus, it appears that TCDD-inducible CYP1A enzymes N-hydroxylate both substrates without selectivity. Together, these findings suggest that CYP3A and CYP2C are the principal isoforms in the cynomolgus monkey, associated with the metabolic activation implicated in the induction of hepatocarcinogenicity by IQ. Furthermore, the poor metabolic activation of MeIQx by CYP3A and CYP2C, coupled with low constitutive levels of CYP1A isozymes, provide a metabolic explanation for the low hepatocarcinogenic potency of MeIQx in cynomolgus monkeys.

In vivo effects of chromium.

The production of reactive oxygen species on addition of hexavalent chromium (potassium dichromate, K2Cr2O7) to lung cells in culture was studied using flow cytometer analysis. A Coulter Epics Profile II flow cytometer was used to detect the formation of reactive oxygen species after K2Cr2O7 was added to A549 cells grown to confluence. The cells were loaded with the dye, 2',7'-dichlorofluorescein diacetate, after which cellular esterases removed the acetate groups and the dye was trapped intracellularly. Reactive oxygen species oxidized the dye, with resultant fluorescence. Increased doses of Cr(VI) caused increasing fluorescence (10-fold higher than background at 200 microM). Addition of Cr(III) compounds, as the picolinate or chloride, caused no increased fluorescence. Electron paramagnetic resonance (EPR) spectroscopic studies indicated that three (as yet unidentified) spectral "signals" of the free radical type were formed on addition of 20, 50, 100, and 200 microM Cr(VI) to the A549 cells in suspension. Two other EPR "signals" with the characteristics of Cr(V) entities were seen at field values lower than the standard free radical value. Liver microsomes from male Sprague-Dawley rats treated intraperitoneally with K2Cr2O7 (130 mumole/kg every 48 hr for six treatments) had decreased activity of cytochromes P4503A1 and/or 3A2, and 2C11. Hepatic microsomes from treated female Sprague-Dawley rats, in contrast, had increased activities of these isozymes. Lung microsomes from male Sprague-Dawley rats had increased activity of P4502C11.

Characterization of rat cytochrome P450 isozymes involved in the covalent binding of cyclosporin A to microsomal proteins.

Cyclosporin A (CsA) is an immunosuppressant drug which is extensively metabolized by the hepatic microsomal monooxygenases. Among other toxicities, CsA is nephrotoxic and hepatotoxic. In the present study, the NADPH-dependent cytochrome P450-supported metabolism of CsA to reactive metabolite(s) capable of covalently binding to proteins was studied. The covalent binding was inhibitable in vitro with classical cytochrome P450 inhibitors. The covalent binding of CsA metabolite(s) was induced six- to eightfold in liver microsomes from rats of both sexes treated with dexamethasone, suggesting that a P450 3A-related protein was involved in the covalent binding of CsA metabolite(s). However, the isozyme responsible was not P450 3A1 or 3A2, since inhibitory monoclonal antibodies to these isozymes did not inhibit the covalent binding. The binding was, however, inhibitable in vitro with cytochrome P450 3A substrates and inhibitors such as erythromycin and triacetyloleandomycin. Greater amounts of CsA covalent binding occurred in liver microsomes from adult uninduced female rats than males or immature rats of either sex. Therefore, a female-specific isozyme of P450 present in adult female rat liver microsomes, which may or may not be identical to a dexamethasone-inducible isozyme, is also involved in the metabolism of CsA to form covalent binding metabolites. The covalent binding of CsA was 50% inhibited by glutathione. However, mannitol and superoxide dismutase did not affect the binding. This suggested that at least some of the metabolites of CsA involved in covalent binding were electrophilic in nature; however, hydroxyl radicals and superoxide anion radicals were not involved.

Effects of phenethyl isothiocyanate, a carcinogenesis inhibitor, on xenobiotic-metabolizing enzymes and nitrosamine metabolism in rats.

Phenethyl isothiocyanate (PEITC), a constituent of cruciferous vegetables, has been shown to inhibit chemical carcinogenesis, possibly due to its ability to block the activation or to enhance the detoxification of chemical carcinogens. The present study was conducted to elucidate the biochemical mechanisms involved by characterizing the effects of PEITC on phase I and phase II xenobiotic-metabolizing enzymes. A single dose of PEITC to F344 rats (1 mmol/kg) decreased the liver N-nitrosodimethylamine demethylase (NDMAd) activity (mainly due to P450 2E1) by 80% at 2 h and the activity of NDMAd remained decreased by 40% at 48 h after treatment. The liver pentoxyresorufin O-dealkylase (PROD) activity and P450 2B1 protein level were elevated 10- and 7-fold at 24 h after treatment respectively. The liver microsomal ethoxyresorufin O-dealkylase (EROD) (mainly due to P450 1A) and erythromycin N-demethylase (mainly due to P450 3A) activities were decreased at 2-12 h after treatment and recovered afterwards. The lung microsomal PROD and EROD activities were not significantly affected; whereas, the nasal microsomal PROD and EROD activities were decreased by 40-50%. After a treatment with PEITC, the rates of oxidative metabolism of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) were decreased in liver microsomes by 40-60% at 2 h and recovered gradually; the rates in lung microsomes were markedly decreased by 60-70% at 2 h and remained at the decreased level at 24 h; and the rates in nasal mucosa microsomes were decreased gradually with the lowest activities observed at 18 h (50%) followed by a gradual recovery. Furthermore, the treatment with PEITC resulted in a maximal 5-fold increase of NAD(P)H:quinone oxidoreductase and 1.5-fold increase of glutathione S-transferase activities in the liver, but the activities of these two enzymes were not significantly affected in the lung and nasal mucosa. The sulfotransferase activity in the liver was decreased by 32-48% at 24-48 h after treatment; the nasal activity was increased by 1.8- to 2.5-fold, but the lung activity was not significantly changed. The hepatic UDP glucuronosyltransferase activity was slightly decreased at 2 h but slightly increased at 48 h after treatment, but no changes were observed for the lung and nasal activities. The study demonstrates that PEITC selectively affects xenobiotic-metabolizing enzymes in the liver, lung and nasal mucosa and it is especially effective in inhibiting the P450-dependent oxidation of NNK in the lung and of NDMA in the liver.