Disposition of nicotine and eight metabolites in smokers and nonsmokers: identification in smokers of two metabolites that are longer lived than cotinine

The disposition of a single intravenous dose of 14C-nicotine was investigated in six cigarette smokers and six nonsmokers. Plasma and urinary elimination of both nicotine and cotinine was faster in smokers than in nonsmokers. In the urine of both smokers and nonsmokers, we identified nicotine and eight metabolites, including two new metabolites: metabolite A (3-hydroxycotinine glucuronide) and metabolite G (demethylcotinine delta 2',3'-enamine). Metabolites A and G were of particular interest because, in smokers, they both persisted longer than cotinine. This property renders them more sensitive than cotinine as potential indicators of passive exposure to cigarette smoke.     

Accelerated metabolism of nicotine and cotinine in pregnant smokers

Cigarette smoking is the foremost modifiable risk factor for adverse pregnancy outcomes. Nicotine is a suspected fetal neuroteratogen. There is concern that nicotine may achieve toxic levels during pregnancy if nicotine replacement therapies are prescribed at doses used in the nonpregnant state. Ten healthy, volunteer, pregnant smokers received infusions of deuterium-labeled nicotine and cotinine during pregnancy and again postpartum. From blood and urine measurements, the following were determined: clearance (renal and nonrenal) of nicotine and cotinine, clearance of nicotine via the cotinine pathway (an indicator of CYP2A6 activity), and daily intake of nicotine from smoking. The clearance of nicotine and cotinine was significantly higher (60 and 140%, respectively), and the half-life of cotinine was much shorter (8.8 versus 16.6 h, P < 0.01) during pregnancy. Although plasma levels of cotinine were lower during pregnancy (119 versus 202 ng/ml, P < 0.05), daily intake of nicotine from smoking was similar during pregnancy and postpartum. For a given level of intake, the pharmacologic and toxicologic effects of nicotine during pregnancy are anticipated to be less than expected from nicotine metabolism data in nonpregnant women. Our data indicate that no downward dose adjustment needs to be made for nicotine replacement therapy during pregnancy. Conversely, higher than usual doses of nicotine may be necessary to optimize efficacy. Lower cotinine levels observed during pregnancy do not necessarily reflect less smoke exposure, and cut-off levels used to classify nonsmokers, passive smokers, and active smokers need to be established for pregnancy.     

Cigarette smoking and theophylline metabolism: effects of cimetidine

The inhibition of theophylline metabolism by cimetidine was investigated in young male cigarette smokers (greater than 20 cigarettes/day) and nonsmokers by stable isotope methodology. Subjects received oral theophylline (510 mg/day) for 14 days and cimetidine (1200 mg/day) over days 1 to 7 or 8 to 14. On days 7 and 14, a tracer dose (10 mg) of stable isotope-labeled theophylline was injected intravenously with the oral dose of theophylline. Serial plasma samples were then obtained for 24 hours and both molecular forms of theophylline were assayed by mass spectrometry after purification by HPLC. Theophylline bioavailability, volume of distribution, and protein binding were of the same order in both groups and were not affected by cimetidine. Although the basal theophylline elimination rate constant was 46% greater and clearance was 54% greater in smokers than in nonsmokers, the proportionate changes in steady-state plasma concentrations, t1/2, and clearance due to cimetidine were much the same in both groups. Plasma thiocyanate concentrations were higher in smokers than in nonsmokers and were related to theophylline clearance. Our findings indicate that cimetidine inhibits theophylline metabolism to a similar extent in both smokers and nonsmokers. Determination of plasma thiocyanate levels may be valuable in the prediction of theophylline clearance.     

Pharmacokinetics of single and multiple doses of ethinyl estradiol and levonorgestrel in relation to smoking

The effects of tobacco and oral contraceptive (OC) use (Ovral) on the pharmacokinetics of levonorgestrel (0.25 mg) and ethinyl estradiol (50 micrograms) were examined. Young women (n = 27) were grouped as follows: I: non-OC users/nonsmokers; II: OC users/nonsmokers; III: non-OC users/smokers; and IV: OC users/smokers. The apparent clearance of levonorgestrel in group I was 80.9 +/- 15.6 ml/hr/kg and the half-life was 19.3 hours. A significant decrease in levonorgestrel clearance was seen in the chronic OC users (groups II and IV). The apparent oral clearance of ethinyl estradiol was 1002 +/- 398 ml/hr/kg in group I and the half-life averaged 7.7 hours. Groups II and III showed decreased (not significant) clearance of ethinyl estradiol. Tobacco use had no effect on steroid pharmacokinetics in the non-OC users. Although chronic OC use did not affect ethinyl estradiol clearance, a joint effect of tobacco/OC use on enhancing clearance of ethinyl estradiol appeared to occur. A linear relationship was found between 24-hour trough serum concentrations and AUC values of both steroids that may facilitate population monitoring studies of OC exposure.     

Effect of smoking on caffeine clearance

The elimination of caffeine from saliva was compared in groups of healthy smokers (n = 13) and nonsmokers (n = 13). Mean caffeine t1/2 in smokers (3.5 hr) was shorter than that in the nonsmokers (6.0 hr). The body clearance of caffeine in the smokers (155 +/- 16 ml . kg-1 . hr-1) was greater than that in the nonsmokers (94 +/- 18 ml . kg-1 . hr-1) (p less than 0.05). No significant difference was noted in the apparent volume of distribution in smokers (720 +/- 67 ml . kg-1) and nonsmokers (610 +/- 80 ml . kg-1). These differences probably reflect the induction of hepatic aryl hydrocarbon hydroxylase (AHH) activity in smokers. The increased clearance of caffeine by smokers may contribute to the higher consumption of coffee reported to occur in this group.     

Cotinine disposition and effects

Cotinine is the major metabolite of nicotine in man. We studied cotinine disposition kinetics in 28 healthy habitual cigarette smokers. Eight subjects received cotinine fumarate, 4 micrograms base/kg/min IV for 60 min. Mean (+/- SD) metabolic clearance was 60 +/- 12 ml/min and mean renal clearance was 12 +/- 5 ml/min, averaging 17% of total clearance. Steady-state volume of distribution was slightly greater than body weight (mean 88 +/- 17 l). Terminal t 1/2 averaged 15.8 +/- 4.0 hr in these eight subjects and 19.7 +/- 6.5 hr in another 12 subjects who abstained from smoking for 3 days. The effect of urinary acidification and alkalinization on renal clearance of cotinine during cigarette smoking was studied in another group of eight subjects. Compared with baseline (mean urinary pH 5.8, renal clearance 12.3 +/- 5.9 ml/min), renal clearance was increased about 50% by urinary acidification (pH 4.4, clearance 18.6 +/- 10 ml/min), but it was not affected by alkalinization (pH 6.7, clearance 14.0 +/- 10.4 ml/min). Infusion of cotinine to blood concentrations seen in moderately heavy smokers had no effect on heart rate, blood pressure, or skin temperature, measures that are sensitive to effects of nicotine. No spontaneous subjective effects were reported. We conclude that, at levels to which cigarette smokers are generally exposed, cotinine exerts no cardiovascular activity and weak, if any, psychologic activity.     

Exposure to environmental tobacco smoke measured by cotinine 125I-radioimmunoassay

We describe a polyclonal-antiserum-based 125I-radioimmunoassay for cotinine that is suitable for measuring nonsmokers' passive exposure to tobacco smoke in the environment. The standard curve ranged from 0.25 to 12.0 micrograms/L, with an estimated lower limit of sensitivity of 0.2 microgram/L (95% B/Bo = 0.2 microgram/L; 50% B/Bo = 4.0 micrograms/L). The median within-assay CVs for patients' samples with cotinine values from 0.4 to 1.3, 1.4 to 2.4, 2.5 to 4.6, and 4.7 to 15.6 micrograms/L were 13.9%, 7.2%, 5.1%, and 5.7%, respectively. Between-assay CVs for two quality-control sera with average values of 1.53 and 3.68 micrograms/L were 14.3% and 7.8%, respectively. Analytical recoveries of cotinine from smokers' sera diluted in zero calibrant ranged from 91% to 116%. Cotinine values determined on 79 paired sera and urines from nonsmokers showed significant correlation with self-reported exposure to environmental tobacco smoke (r = 0.49, P less than 0.001 for sera; r = 0.57, P less than 0.001 for urine). The log of the values for serum and urine cotinine were also significantly correlated (r = 0.85, P less than 0.001). Evidently, polyclonal antiserum can be used to develop a cotinine assay for measuring exposure to environmental tobacco smoke that compares well with that described for monoclonal-based assays.     

Aging and drug interactions. II. Effect of phenytoin and smoking on the oxidation of theophylline and cortisol in healthy men

The effect of age on the induction of theophylline metabolism by phenytoin was examined in healthy young and old male cigarette smokers (greater than or equal to 20 cigarettes/day) and nonsmokers. Two single dose studies of theophylline pharmacokinetics were performed, one as a base-line control and another after a 2-week course of phenytoin. Phenytoin was administered as an i.v. loading dose followed by oral ingestion. The dose was adjusted to achieve total phenytoin plasma concentrations within a low therapeutic range (10-13 micrograms/ml). Free phenytoin concentrations in plasma were slightly higher in old (nonsmokers 0.84 +/- 0.13 micrograms/ml; smokers 0.89 +/- 0.12 micrograms/ml) than in young (nonsmokers 0.75 +/- 0.10 micrograms/ml; smokers 0.72 +/- 0.10 micrograms/ml) subjects, but the differences were not significant. Base-line plasma theophylline clearance was 30% lower in old compared with young nonsmokers (34.0 +/- 2.5 vs. 48.8 +/- 2.6 ml/hr/kg, P less than .001), whereas the small age difference between old and young smokers (86.0 +/- 8.4 vs. 72.4 +/- 8.0 ml/hr/kg) was not significant. Smokers had higher values of theophylline clearance than nonsmokers regardless of age. Half-life was prolonged in old nonsmokers in proportion to decreased clearance, despite a slight decrease in volume of distribution. Phenytoin induced theophylline metabolism to an equal degree in both age groups and in both smokers (young 42.6 +/- 6.5%; old 47.3 +/- 3.6%) and nonsmokers (young 56.3 +/- 8.8%; old 45.4 +/- 6.4%). The magnitude of its induction in smokers was additive to that of cigarette smoking. Old age was associated with a modest selective reduction in N-demethylated metabolic pathways to 3-methylxanthine and 1-methyluric acid, whereas smoking preferentially induced the formation of these products. Phenytoin increased the production of all theophylline primary metabolites to an equal degree in both old and young subjects. The urinary excretion of 6 beta-hydroxycortisol was not influenced significantly by age or smoking and increased 2- to 3-fold in all subject groups with phenytoin. These results confirm earlier observations of a reduction in basal oxidative capacity in elderly nonsmoking males. They also demonstrate that the ability to induce the metabolism of theophylline by smoking or phenytoin and the ability to induce the metabolism of cortisol by phenytoin are maintained in old age.     

Effect of rifampin and tobacco smoking on the pharmacokinetics of ropivacaine.

OBJECTIVE: Our objective was to assess the effect of rifampin (INN, rifampicin) and tobacco smoking on the pharmacokinetics of ropivacaine. METHODS: A randomized, 2-phase, crossover study was performed in both a group of 10 healthy nonsmokers and a group of 8 healthy smokers. In both groups each subject ingested daily for 5 days either placebo or 600 mg rifampin. On day 6 each subject received intravenously over 30 minutes a single dose of 0.6 mg/kg ropivacaine. Ropivacaine, 3-hydroxyropivacaine (3-OH-ropivacaine), and (S) -2',6'-pipecoloxylidide (PPX) in venous plasma and urine were measured for up to 12 hours and 24 hours, respectively. Pharmacokinetic parameters were calculated with noncompartmental methods, and t tests were used for comparisons between the phases and between the smokers and nonsmokers. The electrocardiogram was monitored for 3 hours. RESULTS: There were no statistically significant differences in the area under the plasma concentration-time curve (AUC), plasma clearance (CL), or half-life (t(1/2)) of ropivacaine between the smokers and nonsmokers. However, smokers excreted in urine 31% more 3-OH-ropivacaine and 62% less PPX than nonsmokers did. Rifampin decreased the AUC of ropivacaine in nonsmokers by 52% and in smokers by 38%. In nonsmokers rifampin increased the CL of ropivacaine by 93% and shortened its t(1/2) by 25%. In smokers rifampin increased the CL of ropivacaine by 47% and shortened its t(1/2) by 20%. Rifampin decreased the urinary excretion of 3-OH-ropivacaine in nonsmokers by 74% and in smokers by 68%, and it increased the excretion of PPX by 97% and 158%, respectively. No clinically significant differences in the QTc times were found between the groups or treatments. CONCLUSIONS: Tobacco smoking increases the excretion of 3-OH-ropivacaine in urine, probably because of the increased cytochrome P450 (CYP) 1A2-mediated metabolism of ropivacaine, and decreases the excretion of CYP3A4-formed PPX in urine. Rifampin considerably increases the metabolism of ropivacaine to PPX and decreases the metabolism to 3-OH-ropivacaine in both nonsmokers and smokers.     

Rat hepatic CYP2E1 is induced by very low nicotine doses: an investigation of induction,time course,dose response,and mechanism

CYP2E1 is an ethanol- and drug-metabolizing enzyme that can also activate procarcinogens and hepatotoxicants and generate reactive oxygen species; it has been implicated in the pathogenesis of liver diseases and cancer. Cigarette smoke increases CYP2E1 activity in rodents and in humans and we have shown that nicotine (0.1-1.0 mg/kg s.c. x 7 days) increases CYP2E1 protein and activity in the rat liver. In the current study, we have shown that the induction peaks at 4 h postnicotine (1 mg/kg s.c. x 7 days) treatment and recovers within 24 h. No induction was observed after a single injection, and 18 days of treatment did not increase the levels beyond that found at 7 days. We found that CYP2E1 is induced by very low doses of chronic (x 7 days) nicotine with an ED50 value of 0.01 mg/kg s.c.; 0.01 mg/kg in a rat model results in peak cotinine levels (nicotine metabolite) similar to those found in people exposed to environmental tobacco smoke (passive smokers; 2-7 ng/ml). Previously, we have shown no change in CYP2E1 mRNA, and our current mechanistic study indicates that nicotine does not regulate CYP2E1 expression by protein stabilization. We postulated that a nicotine metabolite could be causing the induction but found that cotinine (1 mg/kg x 7 days) did not increase CYP2E1. Our findings indicate that nicotine increases CYP2E1 at very low doses and may enhance CYP2E1-related toxicity in smokers, passive smokers, and people treated with nicotine (e.g., smokers, patients with Alzheimer's disease, ulcerative colitis or Parkinson's disease).     

Theophylline kinetics in a geriatric group

The influence of age, sex, and smoking on theophylline disposition was studied in 38 healthy subjects ranging in age from 26 to 81 yr. There were 8 young (less than 60 yr) and 30 geriatric (greater than 60 yr) subjects, including 28 men (8 smokers) and 10 women (3 smokers). A crossover experimental design was used. A single dose of theophylline elixir (5 mg/kg lean body weight [LBW]) was given as a reference product to all subjects. One week later a sustained-release (SR) theophylline tablet (8 and 6 mg/kg LBW) was given to the young and the geriatric subjects. Serum theophylline concentrations were determined by HPLC. Theophylline elimination (t1/2 beta) is shorter in the geriatric group (6.93 and 8.14 hr); total body theophylline clearance is greater in the geriatric group (44.39 and 32.97 ml/kg/hr), and the apparent volume of distribution is also greater in the geriatric group (26.29 and 22.97 l). Sex and smoking did not influence any of the parameters studied. In 93% of the geriatric subjects, serum theophylline levels of 8 to 20 micrograms/ml were reached at steady state with the SR tablet. Theophylline dose reduction based on an arbitrary age limit is not, therefore, invariably indicated.     

Reference interval and subject variation in excretion of urinary metabolites of nicotine from non-smoking healthy subjects in Denmark

BACKGROUND: Passive smoking has been found to be a respiratory health hazard in humans. The present study describes the calculation of a reference interval for urinary nicotine metabolites calculated as cotinine equivalents on the basis of 72 non-smokers exposed to tobacco smoke less than 25% of the day. METHODS: Twenty subjects (passive smokers) exposed to tobacco smoke more than 25% of the day (subjectively assessed) and 32 smokers were used to validate the estimated reference interval. Urine samples were collected three times during the day approximately at 06.30, 17.00 and 22.45 h. RESULTS: Within-subject variation was found to be 89.4, 72.6, and 79.2% and between-subject variation was found to be 64.5, 64.2, and 36.1%. No gender difference could be demonstrated. In general all subjects showed increased concentrations in the afternoon and evening samples compared to the morning samples. Parametric reference interval for excretion of nicotine metabolites in urine from non-smokers was established according to International Union of Pure and Applied Chemistry (IUPAC) and International Federation for Clinical Chemistry (IFCC) for use of risk assessment of exposure to tobacco smoke. The reference interval for urinary cotinine was estimated to be 1.1-90.0 micromol/mol creatinine in morning samples from non-smokers. An intercomparison between the radioimmunoassay (RIA) method used for determination of nicotine metabolites and a gas chromatography-mass spectrometry (GC-MS) method for determination of cotinine was carried out on 27 samples from non-smokers and smokers. Results obtained from the RIA method showed 2.84 [confidence interval (CI): 2.50; 3.18] times higher results compared to the GC-MS method. A linear correlation between the two methods was demonstrated (rho=0.96). CONCLUSION: The RIA method is rapid and adequate for clinical use in the assessment of exposure to tobacco smoke, i.e. ratio between CV(a)/CV(ti) was<0.50.     

Clinical-scale high-throughput analysis of urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine by isotope-dilution liquid chromatography-tandem mass spectrometry with on-line solid-phase extraction

BACKGROUND: Quantification of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) in urine or blood is used to assess and monitor oxidative stress in patients. We describe the use of on-line solid-phase extraction (SPE) and isotope-dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) for automated measurement of urinary 8-oxodGuo. METHODS: Automated purification of urine was accomplished with a switching valve and an Inertsil ODS-3 column. After the addition of 15N5-labeled 8-oxodGuo as an internal standard, urine samples were analyzed within 10 min without sample purification. This method was applied to measure urinary 8-oxodGuo in a group of healthy persons (32 regular smokers and 35 nonsmokers). Urinary cotinine was also assayed by an isotope-dilution LC-MS/MS method. RESULTS: The lower limit of detection was 5.7 ng/L on column (2.0 fmol). Inter- and intraday imprecision (CV) was < 5.0%. Mean recovery of 8-oxodGuo in urine was 99%-102%. Mean (SD) urinary concentrations of 8-oxodGuo in smokers [7.26 (3.14) microg/g creatinine] were significantly higher than those in nonsmokers [4.69 (1.70) microg/g creatinine; P < 0.005]. Urinary concentrations of 8-oxodGuo were significantly correlated with concentrations of cotinine in smokers (P < 0.05). CONCLUSIONS: This on-line SPE LC-MS/MS method is sufficiently sensitive, precise, and rapid to provide high-throughput direct analysis of urinary 8-oxodGuo without compromising quality and validation criteria. This method could be applicable for use in daily clinical practice for assessing oxidative stress in patients.     

Ascorbic acid content and accumulation by alveolar macrophages from cigarette smokers and nonsmokers

The lung is at risk for injury from inhaled oxidants, including components of cigarette smoke; therefore, maintaining a chemical antioxidant defense would be advantageous. The potential for ascorbic acid to assume this protective role was investigated by comparing the total ascorbate content of alveolar macrophages obtained from human smokers and nonsmokers, from hamsters that were exposed to cigarette smoke for 4 to 6 weeks, and from a control group of unexposed hamsters. The abilities of alveolar macrophages from these four sources to accumulate 14C-labeled ascorbic acid and dehydroascorbate were also compared. The total ascorbate content in hamster macrophages was 19.5 +/- 1.7 and 44.3 +/- 2.8 nmol/10(7) cells for nonsmokers and smokers, (n = 5) and 73.8 +/- 13.1 nmol/10(7) cells (n = 13, p less than 0.1) for nonsmokers and smokers, respectively. In both humans and hamsters, the rates of accumulation of ascorbic acid and dehydroascorbate were significantly greater (p less than 0.05) for alveolar macrophages from smokers compared with nonsmokers of the same species. After internalization, greater than or equal to 70% of the dehydroascorbate was reduced to ascorbic acid by alveolar macrophages from nonsmokers and smokers of both species. An aqueous extract of cigarette smoke oxidized significantly more ascorbic acid to dehydroascorbate in vitro than a comparable volume of phosphate-buffered saline solution without smoke. The increased content of total ascorbate in alveolar macrophages from smokers and their enhanced ability to accumulate ascorbic acid and dehydroascorbate in vitro may reflect protective utilization of ascorbic acid under conditions of increased oxidant stress, compared with nonsmokers. In addition, alveolar macrophages may internalize dehydroascorbate that has been generated by oxidants in the alveolar space and reduce it to ascorbic acid so it can be reused as an antioxidant.     

Cigarette smoking and theophylline metabolism: effects of phenytoin

The induction of theophylline clearance by phenytoin was investigated in 12 young male subjects (six nonsmokers and six cigarette smokers). Each subject received intravenous theophylline to determine baseline pharmacokinetics. This was followed by an intravenous loading dose of phenytoin sodium and oral maintenance dosing for 2 weeks, after which the intravenous theophylline study was repeated. Phenytoin concentrations were similar in nonsmokers (10.8 +/- 2.0 micrograms/ml) and smokers (11.5 +/- 0.9 micrograms/ml). Control theophylline elimination half-life was 35% less and clearance 88% greater in smokers than in nonsmokers. The proportionate changes in half-life (26.8% +/- 5.6% in smokers and 25.8% +/- 3.5% in nonsmokers) and clearance (48.0% +/- 10.1% in smokers and 39.7% +/- 7.2% in nonsmokers) as the result of phenytoin induction were similar in both groups. These results demonstrate that the induction of theophylline clearance by phenytoin is additive to that caused by cigarette smoking and provide support for the suggestion that theophylline metabolism is influenced by multiple polymorphisms.     

Influence of thyroid function on theophylline kinetics

Theophylline kinetics were examined in five patients with hyperthyroidism before and after treatment with carbimazole. Theophylline clearance fell after carbimazole, but the apparent volume of distribution did not change. There was a correlation between reduction in theophylline clearance and decreased thyroxine serum concentration. Data suggest that maximum induction is reached at a specific level of thyroxine beyond which no further increase in drug metabolizing activity takes place. In 15 subjects treated with aminophylline for acute bronchial obstruction, there was a positive correlation between thyroxine concentration and total body theophylline clearance (r = 0.72 for nonsmokers; r = 0.44 for smokers and nonsmokers).     

Smoking accelerates absorption of inhaled neutrophil elastase inhibitor FK706

PURPOSE: We compared the pharmacokinetics of the inhaled novel neutrophil elastase inhibitor FK706 between healthy nonsmokers and smokers. METHODS: Six healthy nonsmokers and six smokers inhaled 50 to 400 mg FK706 in two different doses. Series of plasma concentrations of the SSS form of FK706 (pharmacologically active epimer) were analyzed model dependently and independently. Pharmacokinetic parameters obtained from each group were compared after standardization by doses. RESULTS: The plasma concentration-time curve of inhaled FK706 was apparently different between smokers and nonsmokers. The maximum plasma concentrations (Cmax) were significantly higher in the smokers than in the nonsmokers (smokers, 1.47 +/- 0.62 ng/mL/mg; nonsmokers, 0.49 +/- 0.14 ng/mL/mg [mean +/- SD; P < .01]). The time to reach Cmax (tmax) and elimination half-life (t1/2) were statistically smaller in the smokers compared with the tmax and elimination t1/2 in the nonsmokers (tmax in smokers, 0.44 +/- 0.27 hours; tmax in nonsmokers, 1.17 +/- 0.39 hours [P < .01]; t1/2 in smokers, 1.23 +/- 0.40 hours; t1/2 in nonsmokers, 2.73 +/- 0.57 hours [P < .01]). The area under the plasma concentration-time curve and plasma clearance were not significantly different between the two groups. Model-dependent pharmacokinetic analysis, assuming a flip-flop model, revealed that the absorption rate constant (ka) was about 10 times greater in smokers than the ka in nonsmokers. CONCLUSION: Significant increases of Cmax and ka and reductions of tmax and elimination t1/2 of the inhaled FK706 were observed in the healthy smokers, suggesting that the smoking habit accelerates the drug absorption after inhalation. These results suggest that we should pay attention to the drug-related adverse events caused by smoking, especially when the drug has a narrow therapeutic range.     

The influence of smoking on plasma homocysteine and cysteine levels in passive and active smokers.

Total plasma homocysteine (tHcy) and cysteine (tCys) levels are associated with cardiovascular diseases. One of the determinants that influence their levels is cigarette smoking. The aim of this study was to determine the relationship between plasma levels of both amino acids and urinary cotinine concentration as a reliable biomarker of tobacco smoke exposure. One hundred and seventeen volunteers (61 women and 56 men) aged 19-60 years (mean 40.3 +/- 11.0) were included in the study. The study subjects were qualified into non-smokers, passive smokers and active smokers based upon the urinary cotinine concentration. In each particular group, plasma tHcy and tCys levels were measured and evaluated in the whole population and separately in women and men. Statistically insignificant differences in plasma tHcy and tCys levels in the whole group of passive smokers in comparison with non-smokers were observed (11.47 vs. 10.94 micromol/l, p=0.414, and 253.0 vs. 266.9 micromol/l, p=0.163, respectively). However, statistically significant differences in plasma tHcy levels (13.29 vs. 10.94 micromol/l, p=0.011) and in plasma tCys levels (218.2 vs. 266.9 micromol/l, p<0.001) were found in the whole group of active smokers compared with non-smokers. The Pearson's coefficient (r) for the correlation between plasma tHcy level and urinary cotinine concentration was r=0.630 (p<0.001) in the whole group of active smokers and r=0.480 (p=0.003) in the whole group of passive smokers. The correlation between plasma tCys level and urinary cotinine concentration in both study groups was insignificant. Similar results were obtained when calculated separately for men and women. The results suggest that cigarette smoking is a strong determinant of plasma tHcy level, but it is not a determinant of plasma tCys level.     

Two automated methods for measuring plasma thiocyanate compared

In an interlaboratory comparison of two continuous-flow analytical procedures for measuring thiocyanate, we used ferric nitrate (y) and p-phenylenediamine/pyridine (x) as colorimetric reagents to measure its concentrations in plasma of 100 consecutive patients attending a peripheral vascular disease clinic. The results correlated well (r = 0.987, p less than 0.001; y = 0.938x + 1.2 mumol/L). However, there were small, systematic, positive differences between the phenylenediamine values and the corresponding ferric nitrate values (paired t = 5.4, p less than 0.001). These differences were linearly related to the means of the pairs of results (r = 0.42, p less than 0.001; y = 0.0739x - 2). Nevertheless, when we used previously determined cutoff points the two sets of SCN concentrations concurred completely in classifying the 100 patients as smokers or nonsmokers. On the basis of self-classification by 71 of these subjects, the measurement techniques had a sensitivity of 91% and a specificity of 75%; when five patients claiming to be nonsmokers but found to have abnormally high values for carboxyhemoglobin (2.7 - 6.9%) were reclassified as smokers, specificity increased to 89%.     

Relationship between smoking status and serum lipids in a hyperlipidemic population and analysis of possible confounding factors.

The aim of our study was to estimate the potential relationship between smoking behavior and other coronary heart disease risk factors in 250 hyperlipidemic patients. We present data obtained through self-reporting of the number of cigarettes smoked per day, measurements of three tobacco markers, and data on dietary habits and lipid variables. We measured cotinine (by HPLC) and thiocyanate and used a recent colorimetric assay for the indirect evaluation of the nicotine metabolites in a single urine specimen. Mean values of nicotine metabolites, expressed as cotinine equivalents, were 6.7, 39.9, and 79.4 mumol/L, respectively, for nonsmokers, light smokers (7.7 cigarettes per day), and heavy smokers (25.8 cigarettes per day). We found that light smokers have higher concentrations of cotinine and nicotine metabolites in proportion to the number of cigarettes smoked per day than do heavy smokers. Thus, the simple colorimetric assay can accurately evaluate smoking status. Hyperlipidemia and smoking are linked by an intricate network of multiple relations. The concentration of high-density lipoprotein (HDL) cholesterol is lower in heavy smokers, and the concentrations of triglycerides and cholesterol are higher. The 0.11 mmol/L difference in HDL cholesterol between light and heavy smokers is close to the results of previous papers; however, when gender, dietary habits (including alcohol intake), and data on body mass index are included in a multiple regression analysis, there is no longer an association between HDL cholesterol concentrations and smoking status. Therefore, these different dietary habits may be confounding factors that partly explain the pattern of lipid variables.