Analysis of synthetic antioxidants in salmon silage using QuEChERS extraction method followed by determination by LC-MS/MS; a single-laboratory validation study.

A new method was developed and in-house validated to determined ethoxyquin (EQ), butylated hydroxyanisole (BHA) and propyl gallate (PG) in fish silage and fish oil used for production of animal feed. Sample pre-treatment comprises use of QuEChERS (quick, easy, cheap, effective, rugged and safe) extraction and gives extracts for liquid chromatography-triple quadrupole mass spectrometry analysis without matrix interferences. The results allow quantification of the antioxidants in all matrices by using deuterated internal standards and calibration curves made in solvent, as well as establishing low detection limits (0.012-0.015 mg/kg) and quantification limits (0.040-0.050 mg/kg) needed regarding the recent suspension of EQ as feed additive within the European Union. The proposed method was validated in terms of linearity, accuracy (relative error, ±1.4%), precision (RSD, ≤2.7%) and recovery (matrix effect, 97-101%) where all the parameters show acceptable results according to recognized guidelines (including EuraChem) within method validation. Combined expanded measurement uncertainty was estimated with a coverage factor of 2 by including all contributors to analytical variation, showing results of ±15% or better. The combined QuEChERS and LC-MS/MS method was successfully applied to salmon silage samples and their corresponding aqueous and oil fractions.

Pharmacokinetics of intraperitoneally instilled aminophylline, terbutaline and tobramycin in pigs.

INTRODUCTION: Venous catheters are sometimes difficult or even impossible to insert and may also be associated with serious complications. This study was carried out to investigate whether intraperitoneal administration of drugs may be an alternative to the intravenous route in patients with limited vascular access. MATERIALS AND METHODS: Three drugs commonly in use in clinical practise, aminophylline, terbutaline and tobramycin, were administered to pigs intravenously and intraperitoneally in small volumes. Serum concentrations were analysed over a period of 6 h and pharmacokinetic key variables for each drug were calculated. RESULTS: Aminophylline (theophylline), terbutaline and tobramycin were absorbed from the peritoneal space and into systemic circulation. For theophylline, the concentration/time profiles after intraperitoneal and after intravenous administration were almost identical, and the intraperitoneal bioavailability was calculated to 0.94. For terbutaline and tobramycin, the intraperitoneal absorption was delayed without any initial peak. Moreover, the intraperitoneal bioavailability was lower than for theophylline (0.71 and 0.65, respectively). CONCLUSION: The pharmacokinetic properties after intraperitoneal administration differed among the three drugs, but the results are encouraging and provide a basis for further investigation in humans.

Influences on serum concentrations of morphine, M6G and M3G during routine clinical drug monitoring: a prospective survey in 300 adult cancer patients.

BACKGROUND: In order to make treatment decisions physicians should have knowledge about the relations between patient characteristics and drug disposition. Dose, route of administration, gender, age and renal function are reported to influence the serum concentrations of morphine, morphine-6-glucurnide (M6G) and morphine-3-glucuronide (M3G) during chronic treatment of cancer pain. These factors, however, are not evaluated in studies with a sample size sufficient to explore predictive factors. METHODS: Three hundred consecutive morphine users admitted because of a malignant disease were recruited. The relations of serum concentrations of morphine, M6G and M3G to patient characteristics (gender, age, weight, renal function, liver function, dose, route of administration) were explored, and regression analysis performed to investigate whether these characteristics predicted serum concentrations obtained during routine clinical drug monitoring. RESULTS: Morphine dose was associated with serum concentrations of morphine (r = 0.69), M6G (r = 0.76) and M3G (r = 0.76). Oral morphine resulted in higher dose-adjusted M6G and M3G serum concentrations compared with s.c. morphine. Creatinine serum concentrations correlated with serum concentrations of M6G and M3G. Dose and route of administration predicted morphine serum concentrations, while dose and renal function predicted M6G and M3G serum concentrations. Age was an additional factor predicting M3G concentrations. Dose was the only factor that explained a clinically significant part of the observed variability. CONCLUSION: Patient characteristics predict only minor parts of the variability of morphine, M3G and M6G serum concentrations observed during routine clinical drug-monitoring in cancer patients.

Fetal growth and length of gestation in relation to prenatal exposure to environmental tobacco smoke assessed by hair nicotine concentration.

We assessed the effects of prenatal exposure to environmental tobacco smoke on fetal growth and length of gestation. The study population consisted of 389 nonsmoking women who were selected from a population-based study in southeast Finland on the basis of questionnaire information after delivery (response rate 94%). The final exposure assessment was based on nicotine concentration of maternal hair sampled after the delivery, which measures exposure during the past 2 months (i.e., the third trimester). The exposure categories were defined a priori as high (nicotine concentration [Greater and equal to] 4.00 microg/g; n = 52), medium (0.75 to < 4.00 microg/g; n = 186), and low as the reference category (< 0.75 microg/g; n = 151). In logistic regression analysis, controlling for confounding, the risk of preterm delivery (< 37 weeks) was higher in the high [adjusted odds ratio (OR) = 6.12; 95% confidence interval (CI), 1.31-28.7] and medium exposure categories (adjusted OR = 1.30; 95% CI, 0.30-5.58) compared with the reference category, and there was a 1.22 (95% CI, 1.07-1.39) increase in adjusted OR with a 1 microg/g increase in hair nicotine concentration. The corresponding adjusted OR was 1.06 (95% CI, 0.96-1.17) for low birth weight and 1.04 (95% CI, 0.92-1.19) for small-for-gestational-age.

Transfer of carisoprodol to breast milk.

There is no published information on the transfer of the centrally acting muscle relaxant carisoprodol and its active metabolite meprobamate into breast milk. The objective of this study was to quantify the excretion of carisoprodol and meprobamate in human milk and estimate the dose received by breast-fed infants. The concentrations of carisoprodol and meprobamate were measured in breast milk on 4 consecutive days at steady-state conditions in one woman using carisoprodol 2100 mg/d. The average milk concentrations were 0.9 microg/mL for carisoprodol and 11.6 microg/mL for meprobamate. Based on the milk concentrations measured, the absolute dose ingested by an exclusively breast-fed infant could be estimated at 1.9 mg/kg per day, and the relative dose would be 4.1% of the weight-adjusted maternal dose. No adverse effects were observed in the infant, but the infant was partly fed with formula because of insufficient maternal milk production. Thus, the authors consider that at least during prolonged use, lactation is generally inadvisable until more clinical data are available.

Effects of a population-based smoking cessation programme on smoking in pregnancy.

A controlled study was conducted to evaluate the effects of a low-intensity population-based smoking cessation programme in maternity care clinics. Quitting smoking during pregnancy was assessed by a self-administered questionnaire and verified by hair nicotine concentration. In the intervention area, 58/306 women (19.0%) reported quitting smoking during pregnancy whereas in the reference area the numbers were 22/152 (14.5%) (difference = 4.5%, 95% confidence interval: -2.6%-11.6%). The intervention group indicated that they received more information on adverse effects of smoking, studied the material more actively, and felt that material from maternity care influenced their smoking behaviour more than the reference group.

Prediction of in vivo metabolic clearance of 25 different petroleum hydrocarbons by a rat liver head-space technique.

In vitro rates of metabolism and Michaelis-Menten constants were determined for 25 different C6 to C10 hydrocarbons using rat liver slices in a vial head-space equilibration system. The rates of metabolism were compared with steady-state levels obtained in vivo in the same strains of rats after inhalation. Aromates were metabolized at a higher rate than naphthenes n-alkanes, isoalkanes and 1-alkenes. The aromates showed, in contrast to the other hydrocarbons investigated, increased metabolism with increasing number of carbon atoms up to C8 (o-xylene, the most extensively metabolized compound). The in vivo steady-state concentrations of the aromates in blood were inversely related to the in vitro efficiency of their metabolism. This explains the pattern of blood levels observed for the C6 to C10 aromates in the rat after inhalation, with o-xylene demonstrating the lowest concentration. In general, the extent of tissue metabolism of the investigated hydrocarbons might be of greater importance for their body distribution than their lipophilicity, especially for the highly metabolized compounds. The high in vitro intrinsic liver clearances found for the aromates indicate a flow-dependent metabolism of these hydrocarbons in vivo. The head-space liver slice equilibration system seems to work adequately for metabolic studies of hydrocarbons with different volatility and water solubility.

Absorption of effervescent paracetamol tablets relative to ordinary paracetamol tablets in healthy volunteers.

OBJECTIVES: The aim of this study was to compare the rate of absorption between ordinary paracetamol tablets and effervescent paracetamol tablets. METHODS: Twenty healthy volunteers participated in an open randomised crossover study and were given a 1000-mg dose of either ordinary paracetamol tablets (2 x 500 mg Panodil tablets, SmithKline Beecham) or effervescent paracetamol tablets (2 x 500 mg Pinex Brusetablett, Alpharma AS) with a 3-week washout period in between. Blood samples were collected for 3 h. Maximum serum concentration (Cmax) and the time to maximum serum concentration (tmax) were recorded and the area under the concentration versus time curve (AUC) was calculated. RESULTS: The mean tmax was significantly shorter when paracetamol effervescent tablets were taken (27 min) rather than ordinary paracetamol tablets (45 min) (P = 0.004). There was no significant difference between the mean Cmax of 143 micromol/l with effervescent tablets and that of 131 micromol/l with ordinary tablets. The mean AUC(0-3 h) was significantly higher with paracetamol effervescent tablets (223.8 micromol x h x l(-1)) than with ordinary tablets (198.2 micromol x h x l(-1); P = 0.003). After 15 min, 17 (85%) subjects in the effervescent group had a serum concentration of 70 micromol/l (lower therapeutic serum concentration) or higher relative to only 2 (10%) subjects in the ordinary tablet group (P = 0.001). CONCLUSION: Paracetamol effervescent tablets are absorbed significantly faster than ordinary paracetamol. Thus, effervescent tablets might offer significantly faster pain relief when paracetamol is used.

Focus on mobilisation after lower abdominal surgery. A double-blind randomised comparison of epidural bupivacaine with morphine vs. lidocaine with morphine for postoperative analgesia.

BACKGROUND: Epidural infusion of morphine, usually with bupivacaine, for postoperative pain relief has proved to be safe and effective. Lidocaine with its short duration of action and low toxicity may be an alternative to bupivacaine. The clinical importance of the choice of local anaesthetic drug on mobilisation after lower abdominal surgery has not been studied previously. METHODS: A total of 52 patients was randomised to epidural infusion of morphine (1.6-4.4 micrograms.kg-1.h-1) with either lidocaine (0.44-0.98 mg.kg-1.h-1) or bupivacaine (0.10-0.28 mg.kg-1.h-1) in a double-blind fashion. The time to mobilisation, degree of pain relief, blood pressure, respiration and motor function were recorded at regular intervals postoperatively for 40 h. Serum concentrations of lidocaine, its main metabolite monoethylglycinexylidide (MEGX) and bupivacaine were measured at 3, 15 and 40 h. RESULTS: There were no significant differences in the clinical characteristics between the two patient groups. There were no significant differences in the time from the end of surgery to the time the patients were able to stand without support (bupivacaine: median 24 h (interquartile range (IQR): 22-31), lidocaine: median 28 h (IQR 23-40), P = 0.15) or were able to walk without support (bupivacaine: median 46 h (IQR 28-62), lidocaine: median 48 h (IQR 35-54), P = 0.78). No significant differences between the groups were recorded with respect to pain relief, blood pressure, respiration, sedation score and motor function. The plasma concentration of lidocaine and bupivacaine increased significantly during the treatment period (P < 0.01 for both drugs), but not the concentration of MEGX. The highest venous lidocaine concentration was 17.5 mumol/l and the highest bupivacaine concentration was 18.8 mumol/l. There was a significant correlation between the concentration of both lidocaine and bupivacaine and the concentration of alpha 1-acid glycoprotein (AAG) (lidocaine: r = 0.77, P < 0.001, bupivacaine: r = 0.60, P < 0.001), suggesting that the free fraction of the drugs did not increase. No patients showed serious signs of toxicity. The epidural infusion rates remained stable in both groups during the study period. CONCLUSION: There were no clinically or statistically significant differences in the postoperative course after lower abdominal surgery in patients who received an epidural infusion of morphine combined with bupivacaine as compared to patients who received morphine with lidocaine. Further clinical studies to establish the place of lidocaine in postoperative epidural analgesia should be performed.

Measurement of HPRT mutations in splenic lymphocytes and haemoglobin adducts in erythrocytes of Lewis rats exposed to ethylene oxide.

Young adult male Lewis rats were exposed to ethylene oxide (EO) via single intraperitoneal (i.p.) injections (10-80 mg kg-1) or drinking water (4 weeks at concentrations of 2, 5, and 10 mM) or inhalation (50, 100 or 200 ppm for 4 weeks, 5 days week-1, 6 h day-1) to measure induction of HPRT mutations in lymphocytes from spleen by means of a cloning assay. N-ethyl-N-nitrosourea (ENU) and N-(2-hydroxyethyl)-N-nitrosourea (HOENU) were used as positive controls. Levels of N-(2-hydroxyethyl)valine (HOEtVal) adducts in haemoglobin (expressed in nmol g-1 globin) were measured to determine blood doses of EO (mmol kg-1 h, mM h). Blood doses were used as a common denominator for comparison of mutagenic effects of EO administered via the three routes. The mean HPRT mutant frequency (MF) of the historical control was 4.3 x 10(-6). Maximal mean MFs for ENU (100 mg kg-1) and HOENU (75 mg kg-1) were 243 x 10(-6) and 93 x 10(-6), respectively. In two independent experiments, EO injections led to a statistically significant dose-dependent induction of mutations, with a maximal increase in MF by 2.3-fold over the background. Administration of EO via drinking water gave statistically significant increases of MFs in two independent experiments. Effects were, at most, 2.5-fold above the concurrent control. Finally, inhalation exposure also caused a statistically significant maximal increase in MF by 1.4-fold over the background. Plotting of mutagenicity data (i.e., selected data pertaining to expression times where maximal mutagenic effects were found) for the three exposure routes against blood dose as common denominator indicated that, at equal blood doses, acute i.p. exposure led to higher observed MFs than drinking water treatment, which was more mutagenic than exposure via inhalation. In the injection experiments, there was evidence for a saturation of detoxification processes at the highest doses. This was not seen after subchronic administration of EO. The resulting HPRT mutagenicity data suggest that EO is a relatively weak mutagen in T-lymphocytes of rats following exposure(s) by i.p. injection, in drinking water or by inhalation.

In vitro screening for metabolic interactions among frequently occurring binary mixtures of volatile organic chemicals in Norwegian occupational atmosphere.

Surveys of Norwegian industrial occupational atmosphere between 1983 to 1996, have identified the 12 most frequent occurring binary combinations of volatile organic chemicals. These combinations were tested in vitro for mutual inhibition or enhancement of metabolism by the head space vial equilibration technique with liver S9 obtained from in vivo untreated or pretreated (with the binary mixture) rats. The in vitro system responded to in vivo pretreatment by increasing the metabolic rate of several potentially toxic organic chemicals such as toluene, xylene, styrene, and dichloromethane. In untreated liver S9, the metabolism of several of the tested binary pairs was inhibited when coexposed in vitro to their most prevalent follower as shown for instance for ethanol (with ethyl acetate), dichloromethane (with styrene) and mutually between toluene and xylene. This inhibitory effect disappeared, however, for several of the solvents when combined with the in vivo induced liver S9, a situation which may be the most relevant for occupational exposure. It is concluded that several metabolic interactions occur between low-molecular weight volatile chemicals found in occupational air. These are both inductive and inhibitory in nature and a further mechanistic evaluation including a higher number of differentiated dosage levels, must be performed before a possible health hazard can be confirmed or rejected for the investigated combinations.

Variability of coumarin 7- and 3-hydroxylation in a Jordanian population is suggestive of a functional polymorphism in cytochrome P450 CYP2A6.

OBJECTIVE: To determine the variability of coumarin 7- and 3-hydroxylation in a human population and to evaluate the evidence for the existence of genetic polymorphism in these pathways. 7-Hydroxylation of coumarin is considered to be a detoxication pathway, whilst 3-hydroxylation, which predominates in rats, leads to hepatotoxicity in the rat. Coumarin metabolic phenotypes could aid in refining the risk evaluation for humans of dietary and environmental exposure to coumarin and for the chronic use of coumarin in high doses as a drug to treat lymphoedema and certain cancers. METHODS: Healthy male and female Jordanian volunteers (n = 103) were administered 2 mg coumarin by mouth and collected their 0-8-h urines. These, together with pre-dose blank urines, were analysed by selected-ion monitoring gas chromatography mass spectrometry for their content of the coumarin metabolites 7-hydroxycoumarin (70HC) and 2-hydroxyphenylacetic acid (2OHPAA), the latter arising from the 3-hydroxylation pathway. RESULTS: After coumarin administration, excretion of both 70HC and 2OHPAA was highly variable. A coumarin metabolic ratio (2OHPAA/7OHC) was suggestive of polymorphism. At least one subject had a metabolic response similar to an individual known to be both phenotypically and genotypically (CYP2A6 gene) 7-hydroxylation-deficient. CONCLUSION: In the light of the finding of high variability and possible polymorphism in both the 7- and 3-hydroxylation of coumarin in a human population. we recommend a reappraisal of the risk evaluation of human exposure to coumarin, particularly in pharmaceutical doses.

Metabolic interaction of n-hexane and methyl ethyl ketone in vitro in a head space rat liver S9 vial equilibration system.

Methyl ethyl ketone pretreatment induced rat liver cytochrome P450 and increased significantly the in vitro metabolism of n-hexane and the formation of 2,5-hexanedione in rat liver S9. No significant changes were, however, found in the levels of the intermediate metabolites 2-hexanol, 2,5-hexanediol or methyl n-butyl ketone. Methyl ethyl ketone added in vitro to untreated (non-induced) liver S9 inhibited in a non-competitive pattern the metabolism of n-hexane and decreased significantly and in a dose-dependent way the levels of methyl n-butyl ketone and 2,5-hexanedione. When methyl ethyl ketone and n-hexane were added in vitro to in vivo methyl ethyl ketone pretreated (induced liver S9, the significant increase in the formation of 2,5-hexanedione was maintained, an increase which was only to a minor extent influenced by the in vitro addition of methyl ethyl ketone. These findings are in agreement with an in vivo induction by methyl ethyl ketone of key enzyme(s) in a generally minor metabolic pathway for the conversion of n-hexane to 2,5-hexanedione in rat liver, a pathway which is not influenced by the presence of methyl ethyl ketone itself. The results obtained in this study indicate that the head space equilibration technique is well suited for screening studies of metabolic interactions between organic solvents.

A single amino acid substitution (Leu160His) in cytochrome P450 CYP2A6 causes switching from 7-hydroxylation to 3-hydroxylation of coumarin.

Human populations are thought to metabolize coumarin almost exclusively by 7-hydroxylation. We have identified an individual who is homozygous for a single amino acid substitution (Leu160His) in the cytochrome P450 CYP2A6 arising from the variant CYP2A6*2 allele. On administration of coumarin (2 mg orally) no detectable 7-hydroxycoumarin was excreted in the 0-8-hr urine, rather, approximately 50% of the dose was eliminated as 2-hydroxyphenylacetic acid, the end-product of coumarin 3-hydroxylation. His immediate family members, who were heterozygous for the CYP2A6*2 allele, excreted little 2-hydroxyphenylacetic acid and mainly 7-hydroxycoumarin, when similarly tested. These findings raise a question regarding human risk evaluations for environmental coumarin exposures, since 7-hydroxylation is regarded as a detoxication pathway, but 3-hydroxylation as the process required to lead to macromolecular covalent binding of coumarin. Persons homozygous for the CYP2A6*2 allele may constitute 1-25% of various populations.

Comparison and in vivo relevance of two different in vitro head space metabolic systems: liver S9 and liver slices.

In vitro systems of high biological organization, e.g. containing intact hepatocytes, have been considered as more reliable for metabolic studies and in vivo predictions of toxicokinetics than subcellular systems. For this reason, the kinetics and metabolism of low-molecular-weight volatile chemicals, i.e. head space elimination of substrate and formation of metabolites, were compared in liver S9 and in liver slices. Two substrates, toluene and n-hexane, were used as they represent differences in metabolic pathways and physical-chemical properties. The two systems responded similarly to diethyldithiocarbamate inhibition and acetone inhibition/induction of cytochrome P-450 mediated metabolism. In contrast to liver S9, liver slices did not respond adequately to phenobarbital induction raising the question of substrate availability for P-450 enzymes in liver slices. Liver slices appeared to be superior to liver S9 when specific metabolic pathways involving phase II enzymes were investigated. However, liver S9 seemed to be at least as good as liver slices for estimation of total metabolic rate constants (Km, Vmax) as a basis for in vivo predictions. As the head space liver S9 system is faster and easier to operate than liver slices, it is a promising screening tool for the metabolism of volatile compounds and metabolic interactions.

Hair nicotine concentrations in mothers and children in relation to parental smoking.

The health effects of environmental tobacco smoke (ETS) exposure constitute a main public health problem. Lack of presice methods for assessing personal tobacco smoke exposure, makes it difficult to estimate the health effects of such exposure. Measuring hair nicotine concentrations could be an improvement in the assessment of personal tobacco smoke exposure. The objective of the present study was to estimate quantitatively the relation between hair nicotine concentrations in mothers and children and tobacco smoke exposure assessed by questionnaires. Mothers' and children's hair nicotine concentrations in the proximal 2 cm of hair were measured in 94 families with children 12-36 months of age: 25 nonsmoking families, 40 families with one smoking parent, and 29 families with both parents smoking. Questionnaire information on tobacco smoke exposure was collected from the same families. In multivariate linear regression analysis, children's nicotine levels were linearly related to daily number of cigarettes smoked at home by both mothers (0.8 mg/g increase per cigarette, 95% confidence interval [CI] 0.43-1.18), and fathers (1.3, 0.81-1.73). Mothers' nicotine levels were linearly related to both personal smoking (2.7, 1.75-3.55) and fathers' smoking at home (2.1,0.74-3.49). Hair nicotine seems to be a good quantitative measure of exposure to tobacco smoke during the previous months both among active and passive smokers. The non-invasive and simple collection procedure makes the method especially suitable for estimating tobacco smoke exposure in children.

Interindividual differences in hair uptake of air nicotine and significance of cigarette counting for estimation of environmental tobacco smoke exposure.

Hair from 80 male subjects, smokers and non-smokers, was exposed continuously in a dynamic exposure chamber to constant nicotine vapour concentrations of 20, 200 or 2000 micrograms/m3 for 72 hr. Subgroups of high and low nicotine adsorbing hair were also exposed intermittantly to environmental tobacco smoke for 8 months. Air and hair concentrations of nicotine were determined by gas chromatography/mass spectrometry. The chamber experiments demonstrated a hair nicotine uptake which followed a second order relation to the applied concentrations of nicotine, y = -0.00018x2 + 0.715x + 1.13, r2 = 0.99999. The function and the experimental points showed linearity up to an air nicotine vapour concentration of about 200 micrograms/m+, covering the most relevant range of environmental exposure. An approximately 7- and 2-fold interindividual variation was observed in the hair uptake rate constant of nicotine vapour for the investigated material within the 10 to 90 and 25 to 75% percentiles, respectively. The factors causing this variation were not identified. It was shown that subject age, hair diameter and hair content of eumelanin were without correlation to the rate constants of hair nicotine uptake. The exposure of subgroups of hair to environmental tobacco smoke showed similar uptake profiles of nicotine as that experienced with exposure to pure nicotine vapour, supporting the relevance of controlled chamber nicotine vapour exposures as a relevant tool for the evaluation of hair nicotine uptake from a more complex environmental situation. Standardized measurements of air nicotine vapour and particulate concentrations in a modern office during 3 hr periodical smoking periods, showed that the number of cigarettes smoked was a poor indicator for the estimation of individual exposure to environmental tobacco smoke constituents. Hair nicotine measurements so far seem to be superior to other suggested methodologies for estimation of environmental tobacco smoke exposure, but further studies should be initiated to identify factors determining the rate constant of hair nicotine uptake.

Inhalation experiments with mixtures of hydrocarbons. Experimental design, statistics and interpretation of kinetics and possible interactions.

The paper describes experimental and statistical methods for toxicokinetic evaluation of mixtures in inhalation experiments. Synthetic mixtures of three C9 n-paraffinic, naphthenic and aromatic hydrocarbons (n-nonane, trimethylcyclohexane and trimethylbenzene, respectively) were studied in the rat after inhalation for 12h. The hydrocarbons were mixed according to principles for statistical experimental design using mixture design at four vapour levels (75, 150, 300 and 450 ppm) to support an empirical model with linear, interaction and quadratic terms (Taylor polynome). Immediately after exposure, concentrations of hydrocarbons were measured by head space gas chromatography in blood, brain, liver, kidneys and perirenal fat. Multivariate data analysis and modelling were performed with PLS (projections to latent structures). The best models were obtained after removing all interaction terms, suggesting that there were no interactions between the hydrocarbons with respect to absorption and distribution. Uptake of paraffins and particularly aromatics is best described by quadratic models, whereas the uptake of the naphthenic hydrocarbons is nearly linear. All models are good, with high correlation (r2) and prediction properties (Q2), the latter after cross validation. The concentrations of aromates in blood were high compared to the other hydrocarbons. At concentrations below 250 ppm, the naphthene reached higher concentrations in the brain compared to the paraffin and the aromate. Statistical experimental design, multivariate data analysis and modelling have proved useful for the evaluation of synthetic mixtures. The principles may also be used in the design of liquid mixtures, which may be evaporated partially or completely.

Uptake, distribution, and formation of hemoglobin and DNA adducts after inhalation of C2-C8 1-alkenes (olefins) in the rat.

Absorption, distribution, elimination and hemoglobin and DNA adduct formation were studied in the rat after inhalation of individual C2-C8 1-alkenes (olefins) at 300 p.p.m., 12 h a day for 3 consecutive days. The concentrations of olefins were measured in blood, lung, brain, liver, kidney and perirenal fat immediately after each exposure and 12 h after the third exposure. DNA adducts were determined by 32P-postlabeling in liver, and lymphocytes sampled immediately after the last exposure. Hemoglobin adducts were determined by GC/MS and GC/MS/MS in erythrocytes sampled immediately after the last exposure. Concentrations of 1-alkenes in blood and organs reached a steady-state level after the first 12 h exposure, and the concentrations 12 h after the last exposure were generally low, except in fat tissue. Concentrations of 1-alkenes in blood and the different tissues increased with increasing number of carbon atoms. In contrast, levels of hemoglobin and DNA adducts decreased with increasing number of carbon atoms. The decrease was most pronounced from C2 to C3. The decrease through the whole homologous series from ethene to 1-octene was most pronounced for hemoglobin adducts followed by the DNA adducts in the lymphocytes. All 1-alkenes caused formation of detectable levels of hemoglobin and DNA adducts, although the levels of hemoglobin adducts after C4-C8 exposure were low. The project illustrates important aspects of the use of biomarkers. The structure-activity approach gives possibilities for extrapolation within the homologous series.

Physical exercise increases plasma concentrations of nicotine during treatment with a nicotine patch.

The effect of physical exercise on plasma nicotine concentrations was studied in eight healthy subjects treated with a nicotine patch releasing 14 mg 24 h-1. After 11 h of patch application, plasma nicotine concentrations were measured before and after 20 min of moderate bicycle exercise, or 20 min of rest. Mean plasma nicotine concentration increased from 9.8 to 11.0 ng ml-1 (P = 0.015) during physical exercise, and fell non-significantly from 10.5 to 10.2 ng ml-1 during rest. The increase in plasma nicotine concentration during exercise is similar to that observed for transdermal nitroglycerin, and may be related to an exercise-induced increase in blood flow in the patch area.