Analysis for commonly abused drugs in urine at selected threshold ("cutoff") concentrations.
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Humans↗
Biomedical subjects
R V Blanke
Publications and source records attributed to R V Blanke.
Stereoselective pharmacokinetics of 3,4-methylenedioxymethamphetamine in the rat.
Studies to characterize the pharmacokinetics of the enantiomers of MDMA were conducted in rats using the iliac arterial cannulation. Two routes of administration, intravenous and subcutaneous, were evaluated at two dose levels for each route [20 and 40 mg/kg (+/-)-MDMA for subcutaneous, 10 and 20 mg/kg (+/-)-MDMA for intravenous administrations]. The average half-life (+/- SD) for all dosing groups was 2.5 +/- 0.8 h for (-)-(R)-MDMA and 2.2 +/- 0.8 h for (+)-(S)-MDMA. The more rapid clearance of (+)-(S)-MDMA compared with (-)-(R)-MDMA is consistent with the area under the curve (AUC) data of the parent drug and its primary metabolite MDA. The mean (+/- SD) AUC S/R ratios of MDMA and MDA were 0.70 +/- 0.05 and 3.1 +/- 0.8, respectively. Following a 20 mg/kg dose of racemic MDMA iv the mean (+/- SD) of the percent dose excreted as (-)-(R)-MDMA, (+)-(S)-MDMA, (-)-(R)-MDA, and (+)-(S)-MDA were 20 +/- 10, 12 +/- 6, 3 +/- 1, and 6 +/- 2, respectively.
3,4-Methylenedioxyamphetamine↗
Identification of metabolites of 3,4-methylenedioxymethamphetamine in rats.
Liquid chromatography with electrochemical detection (LC/ECD) and gas chromatography/mass spectrometry (GC/MS) were used to identify metabolites of N-methyl-3,4-methylenedioxyamphetamine (MDMA) in samples of rat plasma and urine. Several potential metabolites, based on what is known about the metabolism of the desmethyl analog (i.e., MDA), were synthesized as standards to aid in the identification of the MDMA metabolites. MDA and N-methyl-1-(4-hydroxy-3-methoxy-phenyl)-2-aminopropane (3b) were identified in urine by HPLC and confirmed by GC/MS. 1-(4-Hydroxy-3-methyoxyphenyl)2-aminopropane, (3a), N-methyl-1-(3-hydroxy-4-methoxyphenyl)-2-aminopropane (2b) and 1-(3,4-dihydroxyphenyl)-2-aminopropane (4a) were tentatively identified by LC/ECD but insufficient sample size precluded confirmation by mass spectrometry. MDA was also identified in brain and plasma extracts. Because MDA is a metabolite of MDMA in humans, and because it has been speculated that the neurotoxic effects of MDA and MDMA may be due to a metabolite, the results of the present study may ultimately aid our understanding of the neurotoxic mechanism of these drugs of abuse.
3,4-Methylenedioxyamphetamine↗
Determination of 3,4-methylenedioxyamphetamine and 3,4-methylenedioxymethamphetamine enantiomers in whole blood.
A method for the determination of the enantiomeric content of 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxymethamphetamine (MDMA) in microsamples (200 microliters) of whole blood is described. The method involves liquid-liquid extraction of MDA and MDMA from blood and derivatization with the chiral reagent N-trifluoroacetyl-L-prolyl chloride. Separation, identification and quantitation of diastereomeric derivatives is by gas chromatography-mass spectrometry. The analytical range of the assay is from 0.12 ng to 48 ng injected on-column. Details for the synthesis of the enantiomers of MDMA are also provided.
3,4-Methylenedioxyamphetamine↗
Stereochemistry of the metabolism of MDMA to MDA.
The chiral derivatizing reagent N-trifluoroacetyl-L-prolyl chloride (LTPC) was used to form diastereomers of 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-methylenedioxyamphetamine (MDA) which were resolved on an achiral gas chromatographic column using a mass spectrometer as a detector. Rats were subcutaneously dosed with 40 mg/kg of (+/-) MDMA.HCl and blood was obtained by decapitation four hours after dosing. Plasma was separated and extracted. The extract was derivatized on-column with LTPC. In addition to the two MDMA isomers, the demethylated metabolites, S(+) and R(-)-MDA were identified. In all experimental groups (male rats, food deprived male rats, female rats, post partum female rats, and mice) dosed with racemic MDMA, higher levels of the S(+) isomer of MDA relative to the R(-) MDA isomer were observed. This may be significant since it has been shown that the S(+) isomer of MDMA is the more neurotoxic isomer of the racemic drug of abuse MDMA.
3,4-Methylenedioxyamphetamine↗
Evaluation of chlordecone in a two-stage model of hepatocarcinogenesis: a significant sex difference in the hepatocellular carcinoma incidence.
Chlordecone (Kepone) has been extensively studied for its toxicity in male production workers who were exposed to large quantities of this organochlorine pesticide. Concern that these workers might be at an increased risk of developing liver cancer prompted us to test chlordecone in a two-stage rat model of hepatocarcinogenesis. Chlordecone acted largely as a liver tumor promoter rather than as a complete hepatic carcinogen in both male and female Sprague-Dawley rats. Dose-response experiments showed that the hepatocarcinogenic effects of long-term chlordecone administration became undetectable at concentrations in non-initiated rat liver in the same range as those measured in human biopsies taken from exposed workers who exhibited no liver effects. Although the toxicity of chlordecone in women has never been studied, we found a dramatic sex difference in the incidence of malignant liver tumors caused by chlordecone promotion in rats. Frank hepatocellular carcinomas were observed in up to 63% of female rats whose livers were previously 'initiated' with a subcarcinogenic dose of diethylnitrosamine given 24 h after partial hepatectomy, and then 'promoted' by 27 weeks of chlordecone administration. In contrast, none of comparably treated males had malignant liver tumors, even after 44 weeks of 'promotion' with chlordecone. Females in the diethylnitrosamine-initiated/chlordecone-promotion groups also contained gamma-glutamyltranspeptidase-positive 'preneoplastic' hepatocellular foci that were more abundant and larger than those observed in comparably-treated males. Moreover, because similar levels of chlordecone were measured in the livers of both sexes at the end of the experimental period, the development of hepatocellular carcinomas in the diethylnitrosamine-initiated female rats appeared to be due to their increased sensitivity to the promotion treatment.
Animals↗
Reduction in the body content of DDE in the Mongolian gerbil treated with sucrose polyester and caloric restriction.
It has previously been shown that oral administration to rats of sucrose polyester (SPE4), a nonabsorbable lipophilic binding agent, greatly stimulates the fecal excretion of coorally administered DDT5 (R.J. Jandacek, 1982, Drug Metab. Rev., 13, 695-714). To determine whether this agent would stimulate the excretion of persistent metabolites of DDT stored in body tissues, we treated a group of gerbils with [14C]-DDT and monitored the fecal excretion of radioactivity for several months until a terminal, log-linear phase of excretion was observed. At this point, when greater than 75% of the fecal radioactivity was identified as [14C]DDE, we fed the animals diets containing up to 10% sucrose polyester and found that the rate of excretion of radioactivity in the stool promptly increased two to three times as compared to the rate in the preceding control period. Some rats were subjected to a 25-50% restriction in total food allotment, but this produced no significant change in fecal excretion of total radioactivity. However, when food restriction was combined with administration of sucrose polyester, there was a dramatic, eightfold average increase in excretion of fecal radioactivity. This synergistic effect was reversed (within 24 hr) when the animals were transferred to a normal diet. Measurement of total body radioactivity confirmed that food restriction plus sucrose polyester treatment reduced the body content of the pesticide. We conclude that stimulation of intestinal excretion may offer a new approach to treatment of patients exposed to lipophilic environmental contaminants.
Animals↗
Investigation of an acetaldehyde-hemoglobin adduct in alcoholics.
It has been proposed that an ethanol-related adduct is formed with hemoglobin in chronic alcoholics. This proposal is based on the observation that alcoholics were found to have an elevation of minor hemoglobins but normal amounts of glycosylated hemoglobin (HbA1c). Since acetaldehyde is believed to be the primary candidate involved in adduct formation, investigation was focused on this particular compound. This study describes the attempt to isolate and purify an acetaldehyde-hemoglobin adduct in alcoholics by cation-exchange chromatography and m-aminophenylboronic acid affinity chromatography for the purpose of characterization. Using acetaldehyde concentrations of 5 and 10 mM, an acetaldehyde adduct with hemoglobin was formed in vitro, isolated, and characterized. However, a similar adduct could not be isolated in vitro using a pharmacological concentration of 100 microM acetaldehyde nor could this adduct be isolated in human alcoholic subjects.
Acetaldehyde↗
Quality assurance in drug-use testing.
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Humans↗
Characterization of a unique aldo-keto reductase responsible for the reduction of chlordecone in the liver of the gerbil and man.
It has been established that the major metabolic pathway for chlordecone (CD) (Kepone) both in humans and in the Mongolian gerbil is bioreduction of this organochlorine pesticide to chlordecone alcohol (CDOH) in the liver. In the present study we developed a gas-liquid chromatography assay to measure the enzymatic reduction of CD to CDOH in vitro and characterized "CD reductase" activity in gerbil liver cytosol. CD reductase is a cytosolic enzyme readily detectable in liver samples prepared from humans, rabbits, and gerbils, the only species of many tested that convert CD to CDOH in vivo. Gerbil CD reductase exhibited a Km of 2.6 microM, a Vmax of 0.14 nmol/min, and a pH optimum of 6.5. The enzyme activity required NADPH, was sensitive to thiol reagents, and was distributed in all tissues with the highest activities found in the liver, intestine, and kidneys. These results are consistent with CD reductase belonging to the family of enzymes referred to as the "aldo-keto reductases." However, unlike previously described reductases, CD reductase was undetectable in rats, mice, hamsters, or guinea pigs and was insensitive to the model aldehyde and ketone reductase inhibitors, phenobarbital and quercetin, respectively. In addition, CD reductase activity in liver was increased by 38% (p less than 0.01) following treatment of gerbils with CD. We conclude that CD reductase is a novel aldo-keto reductase that is uniquely inducible by its substrate.
Alcohol Oxidoreductases↗
Determination of free valproic acid concentrations using the Amicon Micropartition MPS-1 Ultrafiltration System.
Free valproic acid concentrations were determined using the MPS-1 ultrafiltration device marketed by Amicon with one YMB membrane per device. Valproic acid binding to the membrane was 5.6% of the free valproic acid concentration. The free valproic acid concentration increased as serial ultrafiltrate volumes were collected, suggesting that only small ultrafiltrate volumes should be collected from a large initial sample. The protein content of the ultrafiltrate was acceptable and was within the tolerances stated by Amicon. There was no significant difference between free valproic acid concentrations determined within 3 h of sample collection and those determined after storage at 4 degrees C or -20 degrees C for 1 week. There was no significant difference between free valproic acid concentrations in serum and heparinized plasma samples collected simultaneously.
Humans↗
Isolation of chlordecone binding proteins from pig liver cytosol.
Cytosolic proteins may play an important role in the transport of water insoluble substances through the cytosol to various subcellular locations. The binding of chlordecone (CD) to pig liver cytosolic proteins was studied after the simultaneous administration of [14C]CD and [3H]cholesterol via the portal vein. The isolation of chlordecone binding proteins (CDBPs), from liver cytosol consisted of repeated ultracentrifugation, ammonium sulfate fractionation, and chromatography on Bio-Gel A 0.5m, carboxymethyl cellulose (CMC), and Sephadex G-100. Three proteins retained [14C]CD after elution from the CMC column. CDBP I and CDBP II also retained [3H]cholesterol through this stage of purification, while CDBP III did not. The molecular weights, estimated by Sephadex G-100 gel filtration, were 33,500 and 67,000 for CDBP IA and CDBP IB, 49,000 for CDBP II, and 44,000 for CDBP III. Since dissociation of bound cholesterol could not be avoided during the purification procedures, binding of cholesterol to the CDBPs eluted from Sephadex G-100 was investigated. Incubation of CDBPs with [3H]cholesterol resulted in a 2000-fold increase of 3H associated with CDBP II, an 800-fold increase with CDBP IA, a 100-fold increase for CDBP IB, and a 300-fold increase for CDBP III. The isolation characteristics, molecular weights, and cholesterol binding properties of the CDBPs are compared with cytosolic cholesterol binding proteins previously isolated. The high specific activity binding of both CD and cholesterol by CDBP I and CDBP II suggests that CD and cholesterol share a common transport pathway in the liver cytosol.
Animals↗
High-density lipoproteins decrease the biliary concentration of chlordecone in isolated perfused pig liver.
Chlordecone (CD) is an organochlorine pesticide associated with albumin and high-density lipoproteins (HDL) in the plasma. It is found in higher concentrations in the liver than in other tissues and is excreted in the bile. The influence of plasma HDL on the biliary excretion of CD was studied using isolated pig liver perfused with a Krebs-Ringer bicarbonate solution containing albumin, dextrose, and pig red blood cells. Within 5 min after administration into the perfusion medium of [14C]CD bound to albumin or to HDL, only 13% of the [14C]CD dose remained in the perfusate, showing that CD is rapidly taken up by the liver. After 60 min the plasma concentration was constant at 0.008% dose/ml when [14C]CD was administered bound to albumin in the absence of HDL and at 0.004% dose/ml when administered bound to HDL. The mean concentration of CD in the bile was higher when CD was administered bound to albumin in the absence of HDL (0.039% dose/ml) than when it was administered bound to HDL (0.010% dose/ml). The elimination rate constant of CD from the liver into the bile was 0.007/min whether CD was administered bound to albumin or to HDL. The addition of HDL to the perfusion system after the administration of albumin-bound CD resulted in lower biliary CD concentrations. The results suggest that HDL affects the distribution of CD between the perfusate and liver and between liver and bile. In both cases, distribution toward the liver is favored.
Animals↗
Postmortem stability of barbiturates in blood and tissues.
The stability of five commonly prescribed barbiturates and thiopental in blood and liver at room temperature and at 4 degrees C was studied. Gas chromatography was used for oxybarbiturate analysis while liquid chromatography was used to quantitate thiopental. In blood and liver, greater than 75% of the drugs were detected at the end of the two- to three-month period. These changes were not considered significant; therefore, barbiturates appear to be stable in blood and liver under the conditions of these experiments.
Amobarbital↗
Resources available for patient evaluation.
The availability of resources to aid in the assessment of chemical hazards as etiologic agents of disease is limited. Resources are slowly expanding, however, and the nature of these is discussed.
Environmental Health↗
Chlordecone metabolism in the pig.
The biotransformation of chlordecone (CD) to chlordecone alcohol (CDOH) occurs in man and gerbils but not in rats, guinea pigs and hamsters [1, 2]. Because of the species differences in CDOH formation and the need for a suitable animal model, pigs were administered CD by intraperitoneal (i.p.) injection. Plasma, gallbladder bile, hepatic bile, liver and feces were collected and analyzed by gas chromatography for CD metabolites. CDOH was present in bile and feces with up to 85% conjugated in the bile but only 15% was conjugated in the feces. Up to 20% of the CD in plasma and bile and less than 3% in feces was in the conjugated form. Both reduction and conjugation of CD in the pig are similar to those in man.
Animals↗
Postmortem stability of benzodiazepines in blood and tissues.
The stability of benzodiazepines in blood and tissues was examined in this study. Specifically, diazepam, chlordiazepoxide, flurazepam, and their desalkyl metabolites were studied over several months. Diazepam, flurazepam, and N-1-desalkylflurazepam were stable when stored in blood at room temperature while chlordiazepoxide, norchlordiazepoxide, and nordiazepam were found to be unstable under similar storage conditions. Data from tissues containing these chemicals corroborated the results from blood.
Anti-Anxiety Agents↗