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At least 19 recordsLinked to original sources
PubMed1986

Consumption of pentane by hepatic microsomes and consequences on pentane measurement in exhaled gases.

Pentane measurement in exhaled gases was proposed as a safe method to evaluate the importance of lipoperoxidation in vivo, in man and in animals. However we have observed that pentane, which arises from lipoperoxide decomposition, is significantly consumed by cytochrome P-450-rich liver microsomes. This pentane consumption is completely inhibited after heating the microsomes at 100 degrees C, and is considerably reduced by metyrapone, a cytochrome P-450 inhibitor. Hepatic metabolism of pentane, particularly after cytochrome P-450 induction, constitutes a risk of error, when pentane exhalation is taken as an index of lipoperoxidation in vivo.

Animals↗
PubMed1997

Breath pentane concentrations during labor and the effect of epidural analgesia on the pentane concentration.

Increased lipid peroxidation has been observed in pregnancy and particularly in preeclampsia. Pentane, a by-product of lipid peroxidation, can be measured in exhaled breath, and its measurement is considered a non-invasive method of assessing lipid peroxidation in vivo. We measured pentane levels in the breath of 36 healthy parturient women and examined the effect of epidural analgesia on the pentane level. Single-expiratory breath samples were analyzed by gas chromatography. The breath pentane level was higher during labor (4.88 parts per billion [p.p.b.], 95% confidence interval 3.25-6.51 p.p.b.) than before the induction of labor (3.10 p.p.b., 95% confidence interval 2.01-4.19 p.p.b.). There was a significant decrease in the pentane level after the institution of epidural analgesia (2.27 p.p.b., 95% confidence interval 1.43-3.11 p.p.b.). Our results suggest that labor may be accompanied by an increase in lipid peroxidation, and epidural analgesia reverses this increase.

Journal Article↗
PubMed1982

(2R*,3S*)-1-[125I]Iodo-2,3-bis(4-hydroxyphenyl)pentane ([125I]iodonorhexestrol) and (2R*,3S*)-1-[77Br]Bromo-2,3-bis(4-hydroxyphenyl)pentane ([77Br]bromonorhexestrol), two gamma-emitting estrogens that show receptor-mediated uptake by target tissues in vivo.

Two gamma-emitting estrogen analogues, (2R*,3S*)-1-[125I]iodo-2,3-bis(4-hydroxyphenyl)pentane ([125I]iodonorhexestrol) and (2R*,3S*)-1-[77Br]bromo-2,3-bis(4-hydroxyphenyl]pentane ([77Br]bromonorhexestrol), have been prepared by halide ion displacement on a labile trifluoromethanesulfonate derivative of a suitably protected precursor, followed by mild acid deprotection. Although halide displacement on a more stable tristrifluoromethanesulfonate derivative was successful, the basic conditions required for deprotection of this precursor resulted in destruction of the products by a base-induced spiroelimination reaction. In immature female rats, both of these halonorhexestrols demonstrated preferential uptake by the uterus that could be blocked selectively by coadministration of a large dose of unlabeled estradiol. In a double label comparison with 16 alpha-[125I]iodo-17 beta-estradiol the uterine uptake of [77Br]bromonorhexestrol was notably less selective. Stability studies in vitro and in vitro have indicated that both iodo- and bromonorhexestrol are quite labile, and this lability compromises the selectivity of their uptake by estrogen target tissues in vivo. p-Hydroxyphenethyl halides are known to be unusually prone to a base-catalyzed solvolysis, via cyclization of the phenolate to a spirocyclohexadienone intermediate. This unusual solvolytic mechanism may contribute to the lability of these halonorhexestrols in vivo.

Animals↗
PubMed2005

Polar substituent effects in the bicyclo[1.1.1]pentane ring system: acidities of 3-substituted bicyclo[1.1.1]pentane-1-carboxylic acids.

Experimental gas-phase acidities are reported for a series of 3-substituted (X) bicyclo [1.1.1]pent-1-yl carboxylic acids (1, Y = COOH). A comparison with available calculated data (MP2/6-311++G**// B3LYP/6-311+G**) reveals good agreement. The relative substituent effects are shown to be adequately described by a much lower level of theory (B3LYP/6-31+G*). Various correlations are presented which clearly point to polar field effects as being the origin of the relative acidities.

Journal Article↗
PubMed1996

Gas chromatographic method using photoionization detection for the determination of breath pentane.

Lipid peroxidation is thought to be an important event in the pathogenesis of atherosclerosis. It has been suggested that pentane, which can be formed during the oxidation of omega-6 fatty acids, is a marker of lipid peroxidation. Previous studies have reported elevated breath pentane and serum markers of lipid peroxidation in smokers. However, chromatographic separation of pentane from isoprene in virtually all of these studies was incomplete and the methods used did not resolve pentane into its isomers, n-pentane and isopentane. Additionally, most current methods are complicated, requiring trapping and concentrating steps to obtain adequate sensitivity prior to hydrocarbon analysis. The purpose of the current study was to develop a gas chromatographic system to analyze breath pentane, that addresses the above technical problems and that would provide a simple in vivo method for measuring lipid. n-Pentane and isopentane standards were easily separated from isoprene with a Al2O3/KCI capillary column contained in a portable gas chromatograph equipped with a photoionization detector. The analysis of repeated measures showed a low coefficient of variation for measurements of n-pentane (10%) and isopentane (9%). We measured breath pentane in 27 subjects (15 smokers, 12 non-smokers). There were no significant difference between the baseline and 4 week interval measurements of n-pentane for smokers both before and after cigarette smoking. The within-subject variability data showed that the assay is highly reproducible for both low and high pentane levels in smokers. Smokers were found to have higher levels of both n-pentane and isopentane than non-smokers (P < 0.001). In addition, smokers had further significant elevation of pentane levels 10 min after smoking (P < 0.001), which returned to baseline by 1 h. These studies demonstrate that measurement of breath pentane, using a gas chromatograph with a photoionization detector, is simple and reproducible. Additionally, these results suggest that pentane elevation associated with smoking is secondary to the oxidant effects of cigarette smoke and an important temporal relationship exists between cigarette smoking and breath sample analysis.

Adult↗
PubMed2005

Pentane-1,5-diol as a percutaneous absorption enhancer.

Propylene glycol (propane-1,2-diol) is the only diol widely used in dermatology. Pentane-1,5-diol is mainly used as a plasticizer in cellulose products and adhesives, in dental composites and in brake fluid compositions and as a preservative for grain. However, pentane-1,5-diol is also an effective solvent, water-binding substance, antimicrobial agent and preservative and may therefore replace several ingredients in a skin composition. The release of tri-iodothyroacetic acid (TRIAC) and percutaneous absorption of hydrocortisone and mometasone furoate with either pentane-1,5-diol or propane-1,2-diol and 2-methyl-pentane-2,4-diol (hexylene glycol), respectively, as enhancers was compared. The release of TRIAC was 21% higher when pentane-1,5-diol was used as an enhancer instead of propane-1,2-diol. The percutaneous absorption of hydrocortisone through the skin was increased 12 times with propane-1,2-diol compared to 4.4 times with pentane-1,5-diol. However, the percutaneous absorption of hydrocortisone into the skin was 50% higher with pentane-1,5-diol compared to propane-1,2-diol. There was no significant difference, between the original mometasone furoate cream, with 2-methyl-pentane-2,4-diol, and the new cream with pentane-1,5-diol in the amount of mometasone furoate that was absorbed into the skin and through the skin. However, the cosmetic properties of the new mometasone furoate cream was superior to the original mometasone furoate cream, for examples, no bad odour, more even texture, goes better into the skin and has less greasiness. Pentane-1,5-diol can be used as a technology platform, which adds a series of desirable properties to dermatological preparations and enhances product usability. This will result in improved formulations for a series of major and commonly used dermatological drugs. When used in pharmaceutical topical preparations, pentane-1,5-diol will increase the percutaneous absorption of the active substance and it is an efficient antimicrobial agent that will act as an effective preservative in topical formulations. Pentane-1,5-diol is cosmetically attractive, has low risk for skin and eye irritation compared to other diols, low toxicity risk and no bad odour.

Administration, Cutaneous↗
PubMed1983

Pentane clearance from inspired air by the rat: dependence on the liver.

Pentane, a volatile hydrocarbon, is cleared from inspired air by the rat. We have studied this clearance to learn whether or not it is a function of the liver. Rats were put individually into airtight chambers which contained CO2 absorbent and were connected to an O2 reservoir. Pentane was injected into each chamber and chamber atmosphere was assayed frequently for pentane over 6 h by gas chromatography. Semilog plots of pentane concentration had a rapid distribution phase and a log-linear terminal elimination phase. A chamber clearance value in milliliters at atmosphere cleared per minute per kilogram rat weight was calculated. Nephrectomy had no effect on pentane clearance. Liver injury by thioacetamide (5 mmol/kg) or by CCl4 (75 or 125 microliters/100 g) was associated with a marked decrease in pentane clearance, indicating a major role for the liver in pentane elimination. Treatment of rats with inducers or inhibitors of the hepatic microsomal cytochrome P450 system did not affect their ability to clear pentane. However, administration of ethanol or 4-methyl-pyrazole diminished pentane clearance, suggesting that alcohol dehydrogenase may be involved in pentane metabolism. These findings demonstrate that pentane clearance is a liver function.

Animals↗
PubMed1983

Quantitative evaluation of ethane and n-pentane as indicators of lipid peroxidation in vivo.

The use of exhalation of ethane and n-pentane in experimental animals as parameters of lipid peroxidation led to an examination of pharmacokinetics of both compounds in rats. When rats were exposed, in a closed desiccator jar chamber, to a wide range of ethane concentrations, linear elimination pharmacokinetics were observed. n-Pentane, when concentrations higher than 100 ppm were applied, displayed saturation kinetics. These were formally explained by action of two competing metabolizing pathways or enzymes. Application of preexisting models could describe exhalation of both ethane and n-pentane by untreated control rats. Stimulation of lipid peroxidation by ferrous ions or by carbon tetrachloride resulted in dissimilar quantitative behaviours of ethane and n-pentane. Ethane production rates were enhanced after application of both compounds. Because of relatively slow metabolic eliminations this led to markedly elevated concentrations of ethane in the gas phase of the system. Pentane production rates were simultaneously enhanced. However, difficulties in interpretation arise because of rapid metabolic elimination of n-pentane. Compounds that diminish pentane metabolism are shown to evoke higher pentane concentrations in the system than compounds which only enhance the pentane production rate. Determinations of ethane exhalation should provide a more favourable parameter of lipid peroxidation than exhalation of pentane.

Animals↗
PubMed1993

Elevated breath pentane in heart failure reduced by free radical scavenger.

UNLABELLED: Pentane, a product of lipid peroxidation, has been detected in situations involving ischemic injury. Such injury may be limited if lipid peroxidation can be controlled by antioxidants. The role of lipid peroxidation in chronic heart failure (CHF) was assessed by measuring breath pentane in patients with CHF vs. age matched controls. The effect of a free radical scavenger on pentane released during CHF was also measured. Pentane levels were correlated with the daily dose of captopril, a sulfhydril-containing drug used to treat CHF, which is an angiotensin converting enzyme inhibitor. To separate the scavenging effects of captopril from the pharmacologic effects of converting enzyme inhibitors, a crossover study using a nonsulfhydril inhibitor was used. Patients with CHF excreted (p < 0.005) high concentrations of pentane (5.7 +/- 2.1 vs. control 3.6 +/- 1.2 nmol/l). Patients treated with captopril also had significantly higher (p < 0.05) excretion of pentane than the control patients (4.7 +/- 1.3 vs. 3.6 +/- 1.2 nmol/l). The dose of captopril was inversely proportional to the concentration of pentane excreted (r = 0.55, p < 0.05). Pentane excretion during captopril therapy was significantly lower before (p < 0.01) and after (p < 0.02) nonsulfhydril inhibitor therapy. CONCLUSION: breath pentane is elevated in CHF and it can be reduced by a free radical scavenger. This reduction of pentane excretion is not a converting enzyme inhibitor class effect.

Aged↗
PubMed1982

Lipid peroxidation in isolated rat hepatocytes measured by ethane and n-pentane formation.

Isolated rat hepatocytes (1 X 10(7) cells/ml) were aerobically incubated in Eagle's Minimum Essential Medium which contained 2.0% albumin. As potential parameters of lipid peroxidation ethane and n-pentane formed were measured in samples obtained from the gas phase above the incubation mixture. 15-30 nmol ethane or n-pentane were produced by 10(7) hepatocytes within 90 min. Carbon tetrachloride (CCl4) or ADP-complexed ferrous ions stimulated ethane and n-pentane formation considerably, depending on the concentrations of the compounds. With CCl4 10(7) cells formed max 180 nmol ethane and 140 nmol n-pentane within 90 min incubation, whereas with Fe(II) max 130 nmol ethane and 220 nmol n-pentane could be detected. When n-pentane was added to the gas phase above the incubation mixture containing either medium or medium plus hepatocytes its amount decreased by 30% within the first 5 min of incubation. However, afterwards only minor amounts of n-pentane disappeared, even in the presence of hepatocytes. This indicates that n-pentane equilibrates with the cells suspension under the conditions used. Cell viability, as determined by the release of lactate dehydrogenase into the medium and by the uptake of trypan blue by the cells, and the recovery of the cells decreased only in presence of relatively high concentrations of CCl4, or Fe(II) respectively. However, a maximal effect on ethane and n-pentane formation was reached already with lower concentration.

Adenosine Diphosphate↗
PubMed1999

Cometabolic biodegradation of methyl t-butyl ether by Pseudomonas aeruginosa grown on pentane.

A bacterial strain identified as Pseudomonas aeruginosa was isolated from a soil consortium able to mineralize pentane. P. aeruginosa could metabolize methyl t-butyl ether (MTBE) in the presence of pentane as the sole carbon and energy source. The carbon balance for this strain, grown on pentane, was established in order to determine the fate of pentane and the growth yield (0.9 g biomass/g pentane). An inhibition model for P. aeruginosa grown on pentane was proposed. Pentane had an inhibitory effect on growth of P. aeruginosa, even at a concentration as low as 85 micrograms/l. This resulted in the calculation of the following kinetic parameters (mumax = 0.19 h-1, Ks = 2.9 micrograms/l, Ki = 3.5 mg/l). Finally a simple model of MTBE degradation was derived in order to predict the quantity of MTBE able to be degraded in batch culture in the presence of pentane. This model depends only on two parameters: the concentrations of pentane and MTBE.

Biodegradation, Environmental↗
PubMed1984

Pentane formation during the anaerobic reactions of reticulocyte lipoxygenase. Comparison with lipoxygenases from soybeans and green pea seeds.

The lipoxygenases from reticulocytes, soybeans and green pea seeds produce pentane in an anaerobic assay containing 13Ls-hydroperoxy-9-cis, 11-trans-octadecadienoic acid and 9,12-all-cis-octadecadienoic acid. The presence of oxygen strongly inhibits pentane formation by the three enzymes. Relative to the lipoxygenase activity with linoleic acid as substrate, soybean lipoxygenase is 4-times as effective in pentane formation as the lipoxygenases from reticulocytes or green pea seeds. Pentane formation by the reticulocyte lipoxygenase is completely inhibited by lipoxygenase inhibitors (5,8,11,14-eicosatetraynoic acid, 3-t-butyl-4-hydroxyanisol) but only partially by radical scavengers which do not influence the oxygenase activity (2,6-di-t-butyl-4-hydroxytoluene). From the temperature dependence below 20 degrees C an activation energy of the pentane production by the reticulocyte lipoxygenase of about 28 kJ/mol was calculated, which is somewhat higher than that for the oxygenase activity. During the anaerobic reaction of both reticulocyte and soybean lipoxygenase C18-oxodienes, C13-oxodienes, linoleic acid dimers and a polar compound proposed to be epoxy-hydroxyoctadecenoic acid are produced in a similar pattern. Reticulocyte lipoxygenase produces pentane with submitochondrial particles only under anaerobic conditions after an aerobic preincubation. During the incubation of intact reticulocytes with the calcium ionophore A23187 or arachidonic acid, pentane is released. Preincubation of the cells with lipoxygenase inhibitors completely abolishes the pentane formation. Erythrocytes do not form any pentane under the same experimental conditions.

Anaerobiosis↗
PubMed2001

Basal production of pentane in expired gas from healthy humans.

BACKGROUND: Pentane in exhaled gas is often used as an index of lipoperoxidation, but today, there is no standardization for its measurement. In this study, with our technical experience, we determined basal production of pentane in healthy subjects, and we evaluated variability of pentane flow 1 month later. METHODS: 18 subjects inhaled hydrocarbon-free air (HCFA) in order to realize a lung washout. Ambient air and three samples (at T0, T10, T30 min) of expired gas were concentrated using a "trap-and-purge" procedure. For the analysis of pentane, an Al(2)O(3)/KCl plot column contained in a gas chromatograph equipped with a flame ionization detector was used. RESULTS: After 10 min of washout, mean (+/-SD) exhalation rate of pentane was 1+/-0.6 pmol min(-1) kg(-1). After 30 min of washout, mean (+/-SD) exhalation rate of pentane was 0.7+/-0.5 pmol min(-1) kg(-1). No significant difference in pentane flow was shown 1 month later for eight subjects who repeated the protocol. CONCLUSION: With our results and data of the literature, exhalation rates of pentane from healthy adults appear to range between 0.3 and 2 pmol min(-1) kg(-1). The variability of pentane flow 1 month later seems not very important.

Adult↗
PubMed2002

Biofiltration of methyl tert-butyl ether vapors by cometabolism with pentane: modeling and experimental approach.

Degradation of methyl tert-butyl ether (MTBE) vapors by cometabolism with pentane using a culture of pentane-oxidizing bacteria (Pseudomonas aeruginosa) was studied in a 2.4-L biofilter packed with vermiculite, an inert mineral support. Experimental pentane elimination capacity (EC) of approximately 12 g m(-3) h(-1) was obtained for an empty bed residence time (EBRT) of 1.1 h and inlet concentration of 18.6 g m(-3). For these experimental conditions, EC of MTBE between 0.3 and 1.8 g m(-3) h(-1) were measured with inlet MTBE concentration ranging from 1.1 to 12.3 g m(-3). The process was modeled with general mass balance equations that consider a kinetic model describing cross-competitive inhibition between MTBE (cosubstrate) and pentane (substrate). The experimental data of pentane and MTBE removal efficiencies were compared to the theoretical predictions of the model. The predicted pentane and MTBE concentration profiles agreed with the experimental data for steady-state operation. Inhibition by MTBE of the pentane EC was demonstrated. Increasing the inlet pentane concentration improved the EC of MTBE but did not significantly change the EC of pentane. MTBE degradation rates obtained in this study were much lower than those using consortia or pure strains that can mineralize MTBE. Nevertheless, the system can be improved by increasing the active biomass.

Air Pollutants↗