Biomedical subjects

T S Poet

Publications and source records attributed to T S Poet.

26 records · Page 2Linked to original sources

PubMed1996

Participation of cytochromes P4502B and P4503A in cocaine toxicity in rat hepatocytes.

The contributions of cytochromes P4502B (P4502B) and cytochrome P4503A (P4503A) to the bioactivation of cocaine in hepatocytes isolated from Sprague-Dawley rats were assessed using a number of approaches. Hepatocytes were isolated from rats pretreated with either phenobarbital or dexamethasone. Exposure to from 50 to 500 microM of either cocaine or norcocaine resulted in toxicity in hepatocytes from phenobarbital-induced rats. Hepatocytes from dexamethasone-induced rats displayed greater resistance to toxicity mediated by either compound. Although microsomes from dexamethasone- and phenobarbital-induced rats catalyzed cocaine N-demethylation at the same rate, only inhibition of P4502B activity by chloramphenicol and not inhibition of P4503A activity by troleandomycin was associated with protection against cocaine or norcocaine-mediated toxicity. Further, inhibition of P4502B was only effective in protecting against toxicity in hepatocytes isolated from phenobarbital-induced rats. The effects of phenobarbital induction in rats, dogs, and guinea pigs, and the abilities of purified P4502B proteins from rats, dogs, and rabbits to N-demethylate cocaine were investigated. Cytochromes P4502B from different species exhibited different rates of cocaine N-demethylation; microsomes from the guinea pig were able to N-demethylate cocaine at the fastest rate, followed by the dog and the rat. Expressed human P4502B6 exhibited no ability to either N-demethylate cocaine or produce cocaine- or norcocaine-mediated toxicity in lymphoblastoid cells. These results suggest that, although P4502B and P4503A both catalyze the initial oxidation of cocaine in rats, only P4502Bs are involved in further oxidations leading to toxicity. The importance of P4502Bs toward cocaine bioactivation will depend on species-specific isoform activities.

Animals↗

PubMed1994

Inactivation of cytochromes P450 2B protects against cocaine-mediated toxicity in rat liver slices.

Mechanism-based inactivators of rat liver cytochrome P450 2B1 and 2B2 were used to evaluate the role of these enzymes in the hepatotoxicity of cocaine. Loss of liver microsomal androstenedione 16 beta-hydroxylation was monitored to determine the extent of P450 2B1/2 inactivation by chloramphenicol (CAP) or its 2B-selective analogue, N-(2-p-nitrophenethyl)chlorofluoroacetamide (pNO2C1FA). The effect of P450 2B1/2 inactivation on cocaine-mediated hepatotoxicity was assessed in rat liver slices. Exposure of slices from phenobarbital-induced Lewis rats to CAP concentrations ranging from 100 to 500 microM resulted in a concentration-dependent decrease in P450 2B activity and a corresponding decrease in cytotoxicity as measured by K+ loss following exposure to 1 mM cocaine. Treating slices from PB-induced rats with 250 microM pNO2C1FA protected slices against cocaine-mediated cytotoxicity after exposure to 500 microM cocaine. In vivo administration of 300 mg/kg CAP or 200 mg/kg pNO2C1FA to phenobarbital-induced Lewis rats decreased androstenedione 16 beta-hydroxylation to 30 or 39% of control, respectively, and blocked cocaine-mediated K+ loss in rat liver slices. Rat liver microsomes from animals treated with either CAP or pNO2C1FA displayed approximately 40% of the control rate of cocaine N-demethylation. Experiments with phenobarbital-treated Munich Wistar (WM) rats, which lack 2B2, revealed similar rates of microsomal N-demethylation and comparable in vitro hepatotoxicity to Lewis rats. The capacity of a specific P450 2B1/2 inactivator to protect against cocaine-mediated hepatotoxicity both in vivo and in vitro and the results with the WM rats support the identification of P450 2B1 as a major cocaine bioactivating form.

Animals↗

PubMed1992

Effect of murine retroviral infection on hair and serum levels of cocaine and morphine.

LP-BM5 retrovirally infected female C57BL/6J mice were administered cocaine, morphine or both by daily intraperitoneal injection for 9 weeks. Drug concentrations were measured by radioimmunoassay in serum and in hair extracts. Hair samples obtained from all drug-treated mice were positive for the drug injected, while none of the saline-treated mice had detectable drug levels in hair or serum. The average morphine concentration obtained from non-infected mice was 11 ng/mg hair whereas the amount found in the LP-BM5-infected mice was significantly higher (20 ng/mg hair). Mice injected with both morphine and cocaine were given 50% of the regular dose of each drug and drug levels in the hair of these animals were approximately half that of mice injected with the full dose of the single drug. Non-infected mice treated with both drugs had a mean value of 7 ng morphine/mg hair and 374 ng cocaine/mg hair while retrovirus-infected mice had significantly higher concentrations, 10 ng morphine/mg hair and 1160 ng cocaine/mg hair (P less than 0.001). Serum concentrations of cocaine and morphine were significantly higher (P less than 0.01) in the retrovirus-infected animals from 40 min to 1.5 h. The increased concentrations of cocaine and morphine in serum during retrovirus infection are accompanied by a significant increase in the amount of drug incorporated into the hair matrix. This change indicates that retroviral infection may influence the disposition of these drugs in the systemic circulation.

Age Factors↗

PubMed1991

Stimulation of natural killer cell activity by murine retroviral infection and cocaine.

The effects of cocaine and murine AIDS on natural killer (NK) cell activity in C57BL/6 mice was studied. Cocaine may play a major role in the development and progression to AIDS in the human population. Chronic intraperitoneal injection of cocaine was shown to cause an increase in NK cell activity over those of saline-treated animals. Infection with LP-BM5 murine leukemia retrovirus was also shown to increase NK cell activity. NK cell activity was increased in retrovirally infected mice treated with cocaine beyond that of mice treated with cocaine alone. This study indicates an important immunomodulatory effect of cocaine on NK cell activity, especially when combined with the effects caused by retroviral infection.

Adjuvants, Immunologic↗

PubMed1990

Hair analysis.

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Animals↗

PubMedDate not supplied

Development of an integrated microanalytical system for analysis of lead in saliva and linkage to a physiologically based pharmacokinetic model describing lead saliva secretion.

There is a need to develop reliable portable analytical systems for biomonitoring lead (Pb) in noninvasively collected saliva samples. In addition, appropriate pharmacokinetic analyses are used to quantitate systemic dosimetry based on the saliva Pb concentrations. A portable microfluidics/electrochemical device was developed for the rapid analysis of Pb based on square wave anodic stripping voltammetry, in which a saliva sample flows over an electrode surface, Pb2+ is chemically reduced and accumulated, and the electric potential of the electrode scanned. The system demonstrates a good linear response over a broad Pb concentration range (1-2000 ppb). To evaluate the relationship between saliva and blood Pb, rats were treated with single oral doses ranging from 20 to 500 mg Pb/kg of body weight, and 24 hours later were administered pilocarpine, a muscarinic agonist to induce salivation. To correlate saliva levels with internal dose, blood and saliva were collected and quantitated for Pb by inductively coupled plasma-mass spectrometry (ICP-MS) and by the microanalytical system. The quantitation with the microanalytical system was slightly less (approximately 75-85%) than with ICP-MS; however, the response was linear, with concentration suggesting that it can be used for the quantitation of salivary Pb. To facilitate modeling, a physiologically based pharmacokinetic (PBPK) model for Pb was modified to incorporate a salivary gland compartment. The model was capable of predicting blood and saliva Pb concentration based on a limited data set. These results are encouraging, suggesting that once fully developed the microanalytical system coupled with PBPK modeling can be used as important tools for real-time biomonitoring of Pb for both occupational and environmental exposures.

Animals↗

PubMedDate not supplied

Cocaine metabolite (benzoylecgonine) in hair and urine of drug users.

Two methods of drug detection, urinalysis and hair analysis, were compared with respect to the efficiency of identification of drug use in a population of men living on the Arizona-Mexico border. The standard curve of cannabinoids in urine was linear to 20 ng/mL. The GC/MS levels for all cannabinoids combined in urine were very similar to that obtained by radioimmunoassay (RIA), 91% concordance. Similar results were obtained from samples analyzed dually for the cocaine metabolite benzoylecgonine (BE) after spiking. As determined by RIA of urine, 74% of the subjects were positive for cannabinoids. The majority were in the range of 100-1000 ng/mg creatinine. The pattern of excretion of THC metabolites with respect to the verbally reported time of first use was fairly normal, with the peak rate of elimination 13-24 hours following the last reported use. Washed hair samples were extracted by overnight acid hydrolysis. Urine samples and neutralized hair extracts were analyzed for cocaine and BE by RIA. Of the hair samples, 55% contained cocaine/BE, as compared with only 4.3% of the urine samples. Most hair samples contained cocaine/BE in the range of 25-100 ng/sample (100 mg hair). All hair samples testing negative for cocaine/BE by RIA also tested negative by GC/MS, and four samples containing the highest amounts of cocaine and BE by RIA were similarly found to contain the highest amounts by GC/MS. Hair analysis, therefore, gives a wider window of detection of drug use than does urinalysis and shows merit in the confirmation of cocaine use in small clinical research studies.

Adolescent↗

PubMedDate not supplied

A real-time in-vivo method for studying the percutaneous absorption of volatile chemicals.

Realistic estimates of percutaneous absorption following exposures to solvents in the workplace, or through contaminated soil and water, are critical to understanding human health risks. A method was developed to determine dermal uptake of solvents under non-steady-state conditions using real-time breath analysis in rats, monkeys, and humans. The exhaled breath was analyzed using an ion-trap mass spectrometer, which can quantitate chemicals in the exhaled breath stream in the 1-5 ppb range. The resulting data were evaluated using physiologically-based pharmacokinetic (PBPK) models to estimate dermal permeability constants (Kp) under various exposure conditions. The effects of exposure matrix (soil versus water), occlusion versus non-occlusion, and species differences on the absorption of methyl chloroform, trichloroethylene, and benzene were compared. Exposure concentrations were analyzed before and at 0.5-hour intervals throughout the exposures. The percentage of each chemical absorbed and the corresponding Kp were estimated by optimization of the PBPK model to the medium concentration and the exhaled-breath data. The method was found to be sufficiently sensitive for animal and human dermal studies at low exposure concentrations over small body surface areas, for short periods, using non-steady-state exposure conditions.

Animals↗