Cancer risk estimation of glycidol based on rodent carcinogenicity studies, a multiplicative risk model and in vivo dosimetry.

Here we evaluate a multiplicative (relative) risk model for improved cancer risk estimation of genotoxic compounds. According to this model, cancer risk is proportional to the background tumor incidence and to the internal dose of the genotoxic compound. Furthermore, the relative risk coefficient per internal dose is considered to be approximately the same across tumor sites, sex, and species. In the present study, we demonstrate that the relative risk model is valid for cancer risk estimation of glycidol, a common food contaminant. Published tumor data from glycidol carcinogenicity studies in mice and rats were evaluated in combination with internal dose estimates from hemoglobin adduct measurements in blood from mice and rats treated with glycidol in short-term studies. A good agreement between predicted and observed tumor incidence in responding sites was demonstrated in the animals, supporting a relative risk coefficient that is independent of tumor site, sex, and species. There was no significant difference between the risk coefficients for mice (5.1% per mMh) and rats (5.4% per mMh) when considering internal doses of glycidol. Altogether, this mechanism-based risk model gives a reliable risk coefficient, which then was extrapolated to humans considering internal dose, and background cancer incidence.

3-NOP: ADME studies in rats and ruminating animals.

3-NOP (3-nitrooxypropanol) reduces enteric methane formation in ruminants. A series of ADME studies in rats, lactating goats and beef cattle was performed. 3-NOP was entirely absorbed from the GIT of rats: approximately 75% of the administered 3-NOP was eliminated as carbon dioxide via exhalation and approximately 20% were excreted via urine. 3-NOP is oxidized to 3-nitrooxypropionic acid (NOPA) which is then hydrolyzed to 3-hydroxypropionic acid (HPA) and inorganic nitrate, the major rat plasma metabolites. NOPA is also a plasma metabolite in beef. The metabolism of 3-NOP is fast as indicated by the negligible amounts of 3-NOP found in rat plasma 2 h after dosing. HPA is a naturally occurring metabolite. It is either metabolized into carbon dioxide and acetyl-CoA or into propanoyl-CoA, the latter serves as substrate for gluconeogenesis. Gluconeogenesis is very prominent in lactating ruminants which use propanoyl-CoA as their main carbon source. Thus, the formation of lactose from 3-NOP by lactating goats is not unexpected. Lactose was the major metabolite of 3-NOP in the aqueous phase of milk. The incorporation of 3-NOP into endogenous metabolism makes it difficult to derive a marker residue, however, conservative risk assessment could be based on the measured radioactivity in tissues.

Application of physiologically based pharmacokinetic modeling in predicting drug-drug interactions for sarpogrelate hydrochloride in humans.

BACKGROUND: Evaluating the potential risk of metabolic drug-drug interactions (DDIs) is clinically important. OBJECTIVE: To develop a physiologically based pharmacokinetic (PBPK) model for sarpogrelate hydrochloride and its active metabolite, (R,S)-1-{2-[2-(3-methoxyphenyl)ethyl]-phenoxy}-3-(dimethylamino)-2-propanol (M-1), in order to predict DDIs between sarpogrelate and the clinically relevant cytochrome P450 (CYP) 2D6 substrates, metoprolol, desipramine, dextromethorphan, imipramine, and tolterodine. METHODS: The PBPK model was developed, incorporating the physicochemical and pharmacokinetic properties of sarpogrelate hydrochloride, and M-1 based on the findings from in vitro and in vivo studies. Subsequently, the model was verified by comparing the predicted concentration-time profiles and pharmacokinetic parameters of sarpogrelate and M-1 to the observed clinical data. Finally, the verified model was used to simulate clinical DDIs between sarpogrelate hydrochloride and sensitive CYP2D6 substrates. The predictive performance of the model was assessed by comparing predicted results to observed data after coadministering sarpogrelate hydrochloride and metoprolol. RESULTS: The developed PBPK model accurately predicted sarpogrelate and M-1 plasma concentration profiles after single or multiple doses of sarpogrelate hydrochloride. The simulated ratios of area under the curve and maximum plasma concentration of metoprolol in the presence of sarpogrelate hydrochloride to baseline were in good agreement with the observed ratios. The predicted fold-increases in the area under the curve ratios of metoprolol, desipramine, imipramine, dextromethorphan, and tolterodine following single and multiple sarpogrelate hydrochloride oral doses were within the range of ≥1.25, but <2-fold, indicating that sarpogrelate hydrochloride is a weak inhibitor of CYP2D6 in vivo. Collectively, the predicted low DDIs suggest that sarpogrelate hydrochloride has limited potential for causing significant DDIs associated with CYP2D6 inhibition. CONCLUSION: This study demonstrated the feasibility of applying the PBPK approach to predicting the DDI potential between sarpogrelate hydrochloride and drugs metabolized by CYP2D6. Therefore, it would be beneficial in designing and optimizing clinical DDI studies using sarpogrelate as an in vivo CYP2D6 inhibitor.

Preliminary research on 1-(4-bromo-2-nitroimidazol-1-yl)-3-[(18)F]fluoropropan-2-ol as a novel brain hypoxia PET tracer in a rodent model of stroke.

The synthesis of the new radiotracer precursor 4-Br-NITTP and the radiolabeling of the new tracer 1-(4-bromo-2-nitroimidazol-1-yl)-3-[(18)F]fluoropropan-2-ol (4-Br-[(18)F]FMISO) is reported. The cyclic voltammetry behaviour, neuronal cell toxicity, transport through the brain endothelial cell monolayer, in vivo PET imaging and preliminary calculations of the tracer uptake for a rodent model of stroke were studied for the new compound and the results were compared to those obtained with [(18)F]FMISO, the current gold standard PET hypoxia tracer. The new PET brain hypoxia tracer is more easily reduced, has higher CLogP than [(18)F]FMISO and it diffuses more rapidly through brain endothelial cells. The new compound is non-toxic to neuronal cells and it allows the in vivo mapping of stroke in mice with higher sensitivity. 4-Br-[(18)F]FMISO is a good candidate for further development in ischemic stroke.

Characterization of glycidol-hemoglobin adducts as biomarkers of exposure and in vivo dose.

Hemoglobin adducts have been used as biomarkers of exposure to reactive chemicals. Glycidol, an animal carcinogen, has been reported to form N-(2,3-dihydroxy-propyl)valine adducts to hemoglobin (diHOPrVal). To support the use of these adducts as markers of glycidol exposure, we investigated the kinetics of diHOPrVal formation and its elimination in vitro and in vivo. Five groups of rats were orally administered a single dose of glycidol ranging from 0 to 75mg/kg bw, and diHOPrVal levels were measured 24h after administration. A dose-dependent increase in diHOPrVal levels was observed with high linearity (R(2)=0.943). Blood sampling at different time points (1, 10, 20, or 40days) from four groups administered glycidol at 12mg/kg bw suggested a linear decrease in diHOPrVal levels compatible with the normal turnover of rat erythrocytes (life span, 61days), with the calculated first-order elimination rate constant (kel) indicating that the diHOPrVal adduct was chemically stable. Then, we measured the second-order rate constant (kval) for the reaction of glycidol with N-terminal valine in rat and human hemoglobin in in vitro experiments with whole blood. The kval was 6.7±1.1 and 5.6±1.3 (pmol/g globin per µMh) in rat and human blood, respectively, indicating no species differences. In vivo doses estimated from kval and diHOPrVal levels were in agreement with the area under the (concentration-time) curve values determined in our earlier toxicokinetic study in rats. Our results indicate that diHOPrVal is a useful biomarker for quantification of glycidol exposure and for risk assessment.

Bioactivation of cinnamic alcohol forms several strong skin sensitizers.

Cinnamic alcohol is a frequent contact allergen, causing allergic contact dermatitis (ACD) in a substantial number of individuals sensitized from contacts with fragrances. Hence, cinnamic alcohol is one of the constituents in fragrance mix I (FM I) used for screening contact allergy in dermatitis patients. Cinnamic alcohol lacks structural alerts for protein reactivity and must therefore be activated by either air oxidation or bioactivation to be able to act as a sensitizer. In the present study, we explored the bioactivation of cinnamic alcohol using human liver microsomes (HLM), and the potential pathways for these reactions were modeled by in silico (DFT) techniques. Subsequently, the reactivity of cinnamic alcohol and its metabolites toward a model hexapeptide were investigated. In addition to cinnamic aldehyde and cinnamic acid, two highly sensitizing epoxides previously unobserved in studies of bioactivation were detected in the incubations with HLMs. Formation of epoxy cinnamic aldehyde was shown (both by the liver microsomal experiments, in which no depletion of epoxy cinnamic alcohol was observed after initial formation, and by the very high activation energy found for the oxidation thereof by calculations) to proceed via cinnamic aldehyde and not epoxy cinnamic alcohol.

Pharmacokinetic study of cinnamaldehyde in rats by GC-MS after oral and intravenous administration.

A selective and sensitive method utilizing gas chromatography-mass spectrometry was developed for simultaneous determination of cinnamaldehyde, cinnamyl alcohol, and methyl cinnamate in rat plasma. Cinnamaldehyde and cinnamyl alcohol can inter-convert to one another in rats, thus simultaneous quantifying both analytes provided a reliable and accurate method of assessment. Three qualifying ions (131 m/z, 105 m/z and 92 m/z) were chosen for simultaneous quantification of cinnamaldehyde and its metabolites. In this study, the calibration curves demonstrated a good linearity and reproducibility over the range of 20-2000ng/ml (r(2)≥0.999) for all analytes. Furthermore, the sensitivity of gas chromatography-mass spectrometry revealed sufficient lower limit of quantitation and detection of 20ng/ml and 5ng/ml, respectively, in the pharmacokinetic analysis. The intra- and inter-day precision variations were less than 10.4% and 12.2%, respectively, whilst accuracy values ranged from -8.6% to 14.8%. All analytes were stable in plasma and in processed samples at room temperature for 24h with no significant degradation after three freeze/thaw cycles. A small amount of the administered cinnamaldehyde had long half-life of 6.7±1.5h. In this study, gas chromatography-mass spectrometry was demonstrated to be a powerful tool for the pharmacokinetic studies of rats after intravenous and oral administration of cinnamaldehyde.

f-[18F]fluoroethanol and 3-[18F]fluoropropanol: facile preparation, biodistribution in mice, and their application as nucleophiles in the synthesis of [18F]fluoroalkyl aryl ester and ether PET tracers.

INTRODUCTION: 2-[(18)F]Fluoroethoxy and 3-[(18)F]fluoropropoxy groups are common moieties in the structures of radiotracers used with positron emission tomography. The objectives of this study were (1) to develop an efficient one-step method for the preparation of 2-[(18)F]fluoroethanol (2-[(18)F]FEtOH) and 3-[(18)F]fluoropropanol (3-[(18)F]FPrOH); (2) to demonstrate the feasibility of using 2-[(18)F]FEtOH as a nucleophile for the synthesis of 2-[(18)F]fluoroethyl aryl esters and ethers; and (3) to determine the biodistribution profiles of 2-[(18)F]FEtOH and 3-[(18)F]FPrOH in mice. METHODS: 2-[(18)F]FEtOH and 3-[(18)F]FPrOH were prepared by reacting n-Bu4N[(18)F]F with ethylene carbonate and 1,3-dioxan-2-one, respectively, in diethylene glycol at 165°C and purified by distillation. 2-[(18)F]fluoroethyl 4-fluorobenzoate and 1-(2-[(18)F]fluoroethoxy)-4-nitrobenzene were prepared by coupling 2-[(18)F]FEtOH with 4-fluorobenzoyl chloride and 1-fluoro-4-nitrobenzene, respectively. Biodistribution and PET/CT imaging studies of 2-[(18)F]FEtOH and 3-[(18)F]FPrOH were performed in normal female Balb/C mice. RESULTS: The preparation of 2-[(18)F]FEtOH and 3-[(18)F]FPrOH took 60 min, and their decay-corrected yields were 88.6 ± 2.0% (n = 9) and 65.6 ± 10.2% (n = 5), respectively. The decay-corrected yields for the preparation of 2-[(18)F]fluoroethyl 4-fluorobenzoate and 1-(2-[(18)F]fluoroethoxy)-4-nitrobenzene were 36.1 ± 5.4% (n = 3) and 27.7 ± 10.7% (n = 3), respectively. Imaging/biodistribution studies in mice using 2-[(18)F]FEtOH showed high initial radioactivity accumulation in all major organs followed by very slow clearance. On the contrary, by using 3-[(18)F]FPrOH, radioactivity accumulated in all major organs was cleared rapidly, but massive in vivo defluorination (31.3 ± 9.57%ID/g in bone at 1h post-injection) was observed. CONCLUSIONS: Using 2-[(18)F]FEtOH/3-[(18)F]FPrOH as a nucleophile is a competitive new strategy for the synthesis of 2-[(18)F]fluoroethyl/3-[(18)F]fluoropropyl aryl esters and ethers. Our biodistribution data emphasize the importance of in vivo stability of PET tracers containing a 2-[(18)F]fluoroethyl or 3-[(18)F]fluoropropyl group due to high background and high bone uptake resulting from 2-[(18)F]FEtOH and 3-[(18)F]FPrOH, respectively. This is especially important for their aryl ester derivatives which are prone to in vivo hydrolysis.

Post-operative elimination of sevoflurane anesthetic and hexafluoroisopropanol metabolite in exhaled breath: pharmacokinetic models for assessing liver function.

Sevoflurane (SEV), a commonly used anesthetic agent for invasive surgery, is directly eliminated via exhaled breath and indirectly by metabolic conversion to inorganic fluoride and hexafluoroisopropanol (HFIP), which is also eliminated in the breath. We studied the post-operative elimination of SEV and HFIP of six patients that had undergone a variety of surgeries lasting between 2.5 to 8.5 h using exhaled breath analysis. A classical three compartments pharmacokinetic model developed for the study of environmental contaminants was fitted to the breath data. We found that SEV kinetic behavior following surgery (for up to six days) is consistent across all subjects whereas the production and elimination of HFIP varies to some extent. We developed subject specific parameters for HFIP metabolism and interpreted the differences in the context of timing and dose of anesthesia, type of surgery, and specific host factors. We propose methods for assessing individual patient liver function using SEV as a probe molecule for assessing efficiency of liver metabolism to HFIP. This work is valuable not only for the clinical study of metabolism recovery, but potentially also for the study of the interaction of other manufactured and environmental compounds with human systems biology in controlled exposure and observational studies.

Relative oral bioavailability of glycidol from glycidyl fatty acid esters in rats.

In order to quantify the relative bioavailability of glycidol from glycidyl fatty acid esters in vivo, glycidyl palmitoyl ester and glycidol were orally applied to rats in equimolar doses. The time courses of the amounts of glycidol binding to hemoglobin as well as the excretion of 2,3-dihydroxypropyl mercapturic acids were determined. The results indicate that glycidol is released from the glycidyl ester by hydrolysis and rapidly distributed in the organism. In relation to glycidol, there was only a small timely delay in the binding to hemoglobin for the glycidol moiety released from the ester which may be certainly attributed to enzymatic hydrolysis. In both cases, however, an analogous plateau was observed representing similar amounts of hemoglobin binding. With regard to the urinary excretion of mercapturic acids, also similar amounts of dihydroxypropyl mercapturic acids could be detected. In an ADME test using a virtual double tag (³H, ¹4C) of glycidyl palmitoyl ester, a diverging isotope distribution was detected. The kinetics of the ¹4C-activity reflected the kinetics of free glycidol released after hydrolysis of the palmitoyl ester. In view of this experimental data obtained in rats, it is at present justified for the purpose of risk assessment to assume complete hydrolysis of the glycidyl ester in the gastrointestinal tract. Therefore, assessment of human exposure to glycidyl fatty acid ester should be regarded as an exposure to the same molar quantity of glycidol.

Species differences in toxicokinetic parameters of glycidol after a single dose of glycidol or glycidol linoleate in rats and monkeys.

Glycidol fatty acid esters (GEs) have been identified as contaminants in refined edible oils. Although the possible release of glycidol (G) from GEs is a concern, little is known about the conversion of GEs to G in the human body. This study addressed the toxicokinetics of glycidol linoleate (GL) and G in male Crl:CD(SD) rats and cynomolgus monkeys. Equimolar amounts of GL (341 mg/kg) or G (75 mg/kg) were administered by gavage to each animal. G was found in both species after the G and GL administration, while plasma GL concentrations were below the lower limit of quantification (5 ng/ml) in both species. In rats, the administration of GL or G produced similar concentration-time profiles for G. In monkeys, the C(max) and AUC values after GL administration were significantly lower than those after G administration. The oral bioavailability of G in monkeys (34.3%) was remarkably lower than that in rats (68.8%) at 75 mg/kg G administration. In addition, plasma G concentrations after oral administration at three lower doses of GL or G were measured in both species. In monkeys, G was detected only at the highest dose of G. In contrast, the rats exhibited similar plasma G concentration-time profiles after GL or G administration with significantly higher G levels than those in monkeys. In conclusion, these results indicate that there are remarkable species differences in the toxicokinetics of GEs and G between rodents and primates, findings that should be considered when assessing the human risk of GEs.

Fragrance material review on 2-phenyl-2-propanol.

A toxicologic and dermatologic review of 2-phenyl-2-propanol when used as a fragrance ingredient is presented. 2-Phenyl-2-propanol is a member of the fragrance structural group Aryl Alkyl Alcohols and is a tertiary alcohol. The AAAs are a structurally diverse class of fragrance ingredients that includes primary, secondary, and tertiary alkyl alcohols covalently bonded to an aryl (Ar) group, which may be either a substituted or unsubstituted benzene ring. The common structural element for the AAA fragrance ingredients is an alcohol group -C-(R1)(R2)OH and generically the AAA fragrances can be represented as an Ar-C-(R1)(R2)OH or Ar-Alkyl-C-(R1)(R2)OH group. This review contains a detailed summary of all available toxicology and dermatology papers that are related to this individual fragrance ingredient and is not intended as a stand-alone document. Available data for 2-phenyl-2-propanol were evaluated then summarized and includes physical properties, acute toxicity, skin irritation, skin sensitization, and toxicokinetics data. A safety assessment of the entire Aryl Alkyl Alcohols will be published simultaneously with this document; please refer to Belsito et al. (2012) for an overall assessment of the safe use of this material and all Aryl Alkyl Alcohols in fragrances.

Fragrance material review on 2,2-dimethyl-3-phenylpropanol.

A toxicologic and dermatologic review of 2,2-dimethyl-3-phenylpropanol when used as a fragrance ingredient is presented. 2,2-Dimethyl-3-phenylpropanol is a member of the fragrance structural group Aryl Alkyl Alcohols and is a primary alcohol. The AAAs are a structurally diverse class of fragrance ingredients that includes primary, secondary, and tertiary alkyl alcohols covalently bonded to an aryl (Ar) group, which may be either a substituted or unsubstituted benzene ring. The common structural element for the AAA fragrance ingredients is an alcohol group -C-(R1)(R2)OH and generically the AAA fragrances can be represented as an Ar-C-(R1)(R2)OH or Ar-Alkyl-C-(R1)(R2)OH group. This review contains a detailed summary of all available toxicology and dermatology papers that are related to this individual fragrance ingredient and is not intended as a stand-alone document. Available data for 2,2-dimethyl-3-phenylpropanol were evaluated then summarized and includes physical properties, acute toxicity, skin irritation, mucous membrane (eye) irritation, skin sensitization, phototoxicity, and photoallergy data. A safety assessment of the entire Aryl Alkyl Alcohols will be published simultaneously with this document; please refer to Belsito et al. (2012) for an overall assessment of the safe use of this material and all Aryl Alkyl Alcohols in fragrances.

Fragrance material review on ß,ß,3-trimethyl-benzenepropanol.

A toxicologic and dermatologic review of ß,ß,3-trimethyl-benzenepropanol when used as a fragrance ingredient is presented. ß,ß,3-Trimethyl-benzenepropanol is a member of the fragrance structural group Aryl Alkyl Alcohols and is a primary alcohol. The AAAs are a structurally diverse class of fragrance ingredients that includes primary, secondary, and tertiary alkyl alcohols covalently bonded to an aryl (Ar) group, which may be either a substituted or unsubstituted benzene ring. The common structural element for the AAA fragrance ingredients is an alcohol group -C-(R1)(R2)OH and generically the AAA fragrances can be represented as an Ar-C-(R1)(R2)OH or Ar-Alkyl-C-(R1)(R2)OH group. This review contains a detailed summary of all available toxicology and dermatology papers that are related to this individual fragrance ingredient and is not intended as a stand-alone document. Available data for ß,ß,3-trimethyl-benzenepropanol were evaluated then summarized and includes physical properties, acute toxicity, skin irritation, mucous membrane (eye) irritation, skin sensitization, elicitation, phototoxicity, photoallergy, repeated dose, and genotoxicity data. A safety assessment of the entire Aryl Alkyl Alcohols will be published simultaneously with this document; please refer to Belsito et al. (2012) for an overall assessment of the safe use of this material and all Aryl Alkyl Alcohols in fragrances.

Toxicological assessment of 3-chloropropane-1,2-diol and glycidol fatty acid esters in food.

Fatty acid esters of 3-chloropropane-1,2-diol (3-MCPD) and glycidol are a newly identified class of food process contaminants. They are widespread in refined vegetable oils and fats and have been detected in vegetable fat-containing products, including infant formulas. There are no toxicological data available yet on the 3-MCPD and glycidol esters, and the primary toxicological concern is based on the potential release of 3-MCPD or glycidol from the parent esters by lipase-catalyzed hydrolysis in the gastrointestinal tract. Although 3-MCPD is assessed as a nongenotoxic carcinogen with a tolerable daily intake (TDI) of 2 µg/kg body weight (bw), glycidol is a known genotoxic carcinogen, which induces tumors in numerous organs of rodents. The initial exposure estimates, conducted by Federal Institute for Risk Assessment (BfR) under the assumption that 100% of the 3-MPCD and glycidol are released from their esters, revealed especially that infants being fed commercial infant formula could ingest harmful amounts of 3-MCPD and glycidol. However, the real oral bioavailability may be lower. As this gives rise for toxicological concern, the currently available toxicological data of 3-MCPD and glycidol and their esters are summarized in this review and discussed with regard to data gaps and further research needs.

Simple assay of plasma sevoflurane and its metabolite hexafluoroisopropanol by headspace GC-MS.

The anesthetic sevoflurane can now be delivered over periods of up to 48h using a newly developed medical system, the AnaConDa (anesthetic conserving device). Lack of pharmacokinetic data on sevoflurane and its main metabolite (hexafluoroisopropanol, HFIP) in this indication prompted us to develop a headspace GC-MS method to quantify the two substances. The only previously published method for assaying the two substances could not be adapted to our study since it uses expensive and rarely employed system components together with toxic carbon disulfide as a dilution solvent. The method developed is straightforward and uses the relatively non-toxic solvent undecane as dilution solvent and chloroform as internal standard. The method is linear for a concentration range of 1-150microg/ml, and presents high accuracy and precision. LOD and LOQ are 0.2 and 1microg/ml, with a short analysis time (7.6 min for a single analysis). The method was applied to determine the plasma levels of sevoflurane and HFIP in six patients under 48-h anesthetic sedation delivered via the AnaConDa system. Average sevoflurane and HFIP concentrations plateaued at 75 and 4microg/ml, respectively. Sevoflurane quickly tailed off after inhalation was stopped, and HFIP levels remained low.

A toxicologic and dermatologic assessment of related esters and alcohols of cinnamic acid and cinnamyl alcohol when used as fragrance ingredients.

An evaluation and review of a structurally related group of fragrance materials.

Synthesis and evaluation of anilinohexafluoroisopropanols as activators/modulators of LXRalpha and beta.

A series of branched and unbranched anilinohexafluoroisopropanols related to the known sulfonamide T0901317 were prepared and evaluated as activators/modulators of both LXRalpha and LXRbeta. A structure-activity relationship was established and compounds with high potency on both the receptors were identified. Many compounds showed a tendency toward selectivity for LXRbeta versus LXRalpha. Several analogues were evaluated for effects on plasma lipoprotein levels in mice. A few of these significantly raised HDL-cholesterol levels in plasma but showed markedly different effects on liver triglyceride content, suggesting that this series may yield candidates with improved efficacy/safety profiles compared to existing molecules.

Autoradiographic analysis of mouse brain kinin B1 and B2 receptors after closed head trauma and ability of Anatibant mesylate to cross the blood-brain barrier.

The potent non-peptide B2 receptor (R) antagonist, Anatibant mesylate (Ms) (LF 16-0687 Ms), reduces brain edema and improves neurological function recovery in various focal and diffuse models of traumatic brain injury in rodents. In the present study, alteration of kinin B1 and B2R after closed head trauma (CHT) and in vivo binding properties of Anatibant Ms (3 mg/kg, s.c.) injected 30 min after CHT were studied in mice by autoradiography using the radioligands [125I]HPP-Hoe 140 (B2R), and [125I]HPP-des-Arg10-Hoe 140 (B1R). Whereas B1R is barely detected in most brain regions, B2R is extensively distributed, displaying the highest densities in the hindbrain. CHT was associated with a slight increase of B1R and a decrease of B2R (10-50%) in several brain regions. Anatibant Ms (Ki = 22 pM) displaced the B2R radioligand from its binding sites in several areas of the forebrain, basal ganglia and hindbrain. Displacement was achieved in 1 h and persisted at 4 h post-injection. The inhibition did not exceed 50% of the total specific binding in non-injured mice. After CHT, the displacement by Anatibant Ms was higher and almost complete in the cortex, caudate putamen, thalamus, hippocampus, medial geniculate nucleus, ventral tegmental area, and raphe. Evans blue extravasation in brain tissue at 4 h after CHT was abolished by Anatibant Ms. It appeared that Anatibant Ms penetrated into the brain in sufficient amounts, particularly after disruption of the blood-brain barrier, to account for its B2R-mediated neuro- and vascular protective effects. The diminished binding of B2R after CHT may reflect the occupancy or internalization of B2R following the endogenous production of bradykinin (BK).

Synthesis and preliminary biological evaluation of the 99mTc labeled nitrobenzoimidazole and nitrotriazole as tumor hypoxia markers.

1-(3-1,2,4-Nitrotriazole-1-yl)-propanhydroxyiminoamide and 1-(6-nitrobenzoimidazole-1-yl)-propanhydroxyiminoamide were synthesized and radiolabeled with (99m)Tc. The (99m)Tc labeled complexes continuously accumulated in hypoxic murine sarcoma S180 cells in vitro but not in aerobic cells. Biodistribution results in mice bearing S180 tumor indicated that the tracers could localize in tumor and eliminate from it slowly. These results suggested that the (99m)Tc labeled nitrobenzoimidazole and nitrotriazole might be the novel tumor hypoxia markers.