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Solubilization of beta-carotene in culture media.

Several methods were evaluated for the solubilization of supraphysiological concentrations of beta-carotene in culture media. The addition of beta-carotene in ethanol as 0.1% (vol/vol) of culture medium that contained 10% fetal bovine serum and incubation at 37 degrees C for 30 minutes solubilized approximately 50% of the added carotenoid. Solubilized beta-carotene concentrations from 3.06 to 36.4 mumol/l were obtained by this method. Ultracentrifugation studies localized the solubilized beta-carotene to low-density lipoproteins (67.0%) and high-density lipoproteins (24.9%). Other methods utilizing various amounts of fetal bovine serum, ethanol, and hexane as solvents did not significantly improve the solubilization of beta-carotene compared with the use of ethanol as 0.1% (vol/vol) of culture medium that contained 10% fetal bovine serum. Nonetheless, solubilization of supraphysiological concentrations of beta-carotene indicated the feasibility of preparing culture media containing physiological concentrations (approximately 0.5 mumol/l) of beta-carotene.

Animals↗

Thermoanaerobacter mathranii sp. nov., an ethanol-producing, extremely thermophilic anaerobic bacterium from a hot spring in Iceland.

The extremely thermophilic ethanol-producing strain A3 was isolated from a hot spring in Iceland. The cells were rod-shaped, motile, and had terminal spores; cells from the mid-to-late exponential growth phase stained gram-variable but had a gram-positive cell wall structure when viewed by transmission electron microscopy. Strain A3 used a number of carbohydrates as carbon sources, including xylan, but did not utilize microcrystalline cellulose. Fermentation end products were ethanol, acetate, lactate, CO2, and H2. The temperature optimum for growth was between 70 and 75 degrees C, and growth occurred in the range of 50-75 degrees C. The pH range for growth was 4.7-8.8, with an optimum at pH 7.0. Strain A3 was sensitive to tetracycline, chloramphenicol, penicillin G, neomycin, and vancomycin at 100 mg/l but was not sensitive to chloramphenicol and neomycin at 10 mg/l, which indicates that strain A3 belongs to the eubacteria. Addition of 50.66 kPa H2 or 2% NaCl did not affect growth. The isolate grew in the presence of exogenously added 4% (w/v) ethanol. The G+C ratio was 37 mol%. 16S rDNA studies revealed that strain A3 belongs to the genus Thermoanaerobacter. Genotypic and phenotypic differences between strain A3 and other related species indicate that strain A3 can be assigned to a new species, and the name Thermoanaerobacter mathranii is proposed.

Bacteria, Anaerobic↗

II. Functional consequences of intragastrically administered ethanol in rats as measured by the 2-[14C]deoxyglucose method: the contribution of dopamine.

As outlined in the companion paper, many of the changes in functional activity produced by acute intragastric ethanol administration as determined by the quantitative autoradiographic 2-[14C]deoxyglucose method occur in structures of the mesocorticolimbic and nigrostriatal dopamine circuits. In this study, a dopaminergic antagonist, flupenthixol, was used to determine the contribution of dopamine to the ethanol-induced increases in functional activity. To assess the ability of flupenthixol to block dopaminergic-induced increases in glucose utilization, it was first examined in conjunction with the indirect dopaminergic agonist methylphenidate. Pretreatment with flupenthixol significantly reduced methylphenidate-induced increases in glucose utilization in structures of the mesocorticolimbic and nigrostriatal dopamine circuits. These findings indicate that this is an effective strategy for the determination of the neurochemical contributions to the changes in CNS functional activity. Flupenthixol pretreatment blocked many of the ethanol-induced increases in glucose utilization at the 0.25 g/kg dose, particularly in mesocorticolimbic and nigrostriatal structures. At the 1.0 and 2.0 g/kg ethanol doses, however, pretreatment with flupenthixol did not reverse the increases in glucose utilization in several brain regions, suggesting that dopaminergic activity is not responsible for the observed increases in glucose utilization and further, that these increases involve other neurotransmitter systems. In some regions, however, flupenthixol pretreatment resulted in augmented levels of glucose utilization above those rates produced by the administration of higher doses of ethanol alone. These findings suggest that the contribution of dopamine to the increases in functional activity are more complex at higher doses of ethanol.

Administration, Oral↗

Behavioral and subjective effects of ethanol: relationship to cerebral metabolism using PET.

This study examined the effects of ethanol on regional cerebral metabolic rate using positron emission tomography (PET). The study explored the relationship between the mood-altering effects of ethanol and its effects on regional cerebral glucose utilization (CMRglu) in eight healthy male volunteers. In the first phase of the study, the subjects participated in a behavioral preference procedure conducted in a recreational environment to determine their responses to ethanol (0.5 g/kg) in a naturalistic setting. They then participated in three PET sessions, receiving at three to seven day intervals, in counterbalanced order, placebo, 0.5 g/kg or 0.8 g/kg ethanol. PET scans were conducted using a PETT-VI scanner with F-18-2-fluoro-2-deoxyglucose (FDG) as the tracer. The mood-altering effects of ethanol were measured in both the naturalistic and the PET phases of the study. Ethanol produced comparable effects on mood in the naturalistic and the PET settings (i.e., increases in positive mood). The lower dose of ethanol produced variable effects on whole brain and regional CMRglu across subjects. There was some suggestion that certain regional metabolic changes after ethanol were correlated with subjective responses to the drug. The higher dose of ethanol decreased whole brain CMRglu in most subjects. All regions were affected about equally. It was concluded that the mood-altering effects of ethanol are not related in a simple manner to regional changes in CMRglu.

Adult↗

[Cardiac effects of insulin in ethanol intoxication and in the postintoxication period].

Insulin (2 IU/ml) effect on the contractile function, glucose consumption and lactate release by the myocardium was studied in experiments on the isolated rat heart performed at different time after a single (8 g/kg) and 10-fold with a 12-hour interval (8-10 g/kg) intragastric administration of ethanol. A single administration of ethanol failed to influence the contractile function, glucose consumption and lactate release by the isolated heart. The magnitude of a positive inotropic reaction to insulin increased and its stimulating effect on glucose utilization by the myocardium weakened. The reaction of ethanol withdrawal developing after its 10-fold administration led to a disturbance of the contractile and rhythmic functions of the heart and activation of glycolysis. The heart inotropic reaction to insulin in this period weakened and glucose consumption and lactate release stimulated by insulin did not differ from control. During perfusion of intact rat hearts with and without glucose insulin (2 IU/ml) weakened the cardiodepressive effect of ethanol (200 mM).

Alcoholic Intoxication↗

Regulation of nitrate reductase activity in Mycobacterium tuberculosis by oxygen and nitric oxide.

Nitrate reduction by Mycobacterium tuberculosis is regulated by control of the transport of nitrate into the cell by NarK2. When oxygen was introduced into hypoxic cultures, nitrite production was quickly inhibited. The nitrate-reducing enzyme itself is relatively insensitive to oxygen, suggesting that the inhibition of nitrite production by oxygen was a result of interference with nitrate transport. This was not due to degradation of NarK2, as the inhibition was reversed by the removal of oxygen although chloramphenicol prevented new synthesis of NarK2. The oxidant potassium ferricyanide was added to anaerobic cultures to produce a positive redox potential in the absence of oxygen. Nitrite production decreased, signifying that oxidizing conditions, rather than oxygen itself, were responsible for the inhibition of nitrate transport. Nitric oxide added to cultures allowed NarK2 to be active even in the presence of oxygen. A similar result was obtained with hydroxylamine and ethanol, both of which interfere with oxygen utilization and the electron transport chain. It is proposed that NarK2 senses the redox state of the cell, possibly by monitoring the flow of electrons to cytochrome oxidase, and adjusts its activity so that nitrate is transported under reducing, but not under oxidizing, conditions.

Anion Transport Proteins↗

Mechanisms underlying the differential effects of ethanol on the bioavailability of riboflavin and flavin adenine dinucleotide.

Chronic alcoholism is associated with a high prevalence of riboflavin deficiency. Experiments were designed in an animal model to determine whether ethanol alters selectively the absorption of riboflavin and flavin adenine dinucleotide (FAD), the predominant dietary form of the vitamin. Rats received by gavage a liver homogenate to which either [14C]riboflavin or [14C]FAD was added with either ethanol or isocaloric sucrose solutions. Ethanol markedly diminished the bioavailability of [14C]FAD to a greater degree than that of [14C]riboflavin. Corroboration of an ethanol-impaired intraluminal hydrolysis of FAD was provided by using everted jejunal segments and measuring mucosal uptake of [14C]riboflavin together with nonradiolabeled FAD. In subsequent studies with mucosal cell extracts, ethanol markedly inhibited activities of FAD pyrophosphatase and flavin mononucleotide (FMN) phosphatase. These findings suggest that dietary sources of riboflavin (FMN and FAD) are not absorbed as well in the presence of ethanol than are vitamin preparations containing riboflavin, which is utilized more readily.

Acetaldehyde↗

Dilute acid pretreatment, enzymatic saccharification, and fermentation of rice hulls to ethanol.

Rice hulls, a complex lignocellulosic material with high lignin (15.38 +/- 0.2%) and ash (18.71 +/- 0.01%) content, contain 35.62 +/- 0.12% cellulose and 11.96 +/- 0.73% hemicellulose and has the potential to serve as a low-cost feedstock for production of ethanol. Dilute H2SO4 pretreatments at varied temperature (120-190 degrees C) and enzymatic saccharification (45 degrees C, pH 5.0) were evaluated for conversion of rice hull cellulose and hemicellulose to monomeric sugars. The maximum yield of monomeric sugars from rice hulls (15%, w/v) by dilute H2SO4 (1.0%, v/v) pretreatment and enzymatic saccharification (45 degrees C, pH 5.0, 72 h) using cellulase, beta-glucosidase, xylanase, esterase, and Tween 20 was 287 +/- 3 mg/g (60% yield based on total carbohydrate content). Under this condition, no furfural and hydroxymethyl furfural were produced. The yield of ethanol per L by the mixed sugar utilizing recombinant Escherichia colistrain FBR 5 from rice hull hydrolyzate containing 43.6 +/- 3.0 g fermentable sugars (glucose, 18.2 +/- 1.4 g; xylose, 21.4 +/- 1.1 g; arabinose, 2.4 +/- 0.3 g; galactose, 1.6 +/- 0.2 g) was 18.7 +/- 0.6 g (0.43 +/- 0.02 g/g sugars obtained; 0.13 +/- 0.01 g/g rice hulls) at pH 6.5 and 35 degrees C. Detoxification of the acid- and enzyme-treated rice hull hydrolyzate by overliming (pH 10.5, 90 degrees C, 30 min) reduced the time required for maximum ethanol production (17 +/- 0.2 g from 42.0 +/- 0.7 g sugars per L) by the E. coli strain from 64 to 39 h in the case of separate hydrolysis and fermentation and increased the maximum ethanol yield (per L) from 7.1 +/- 2.3 g in 140 h to 9.1 +/- 0.7 g in 112 h in the case of simultaneous saccharification and fermentation.

Carbohydrate Metabolism↗

Conversion of Cellulose to Methane and Carbon Dioxide by Triculture of Acetivibrio cellulolyticus, Desulfovibrio sp., and Methanosarcina barkeri.

The fermentation of cellulose by monocultures of Acetivibrio cellulolyticus and cocultures of A. cellulolyticus-Methanosarcina barkeri, A. cellulolyticus-Desulfovibrio sp., and A. cellulolyticus-M. barkeri-Desulfovibrio sp. was studied. The monoculture produced ethanol, acetate, H(2), and CO(2). More acetate and less ethanol was formed by the cocultures than by the monoculture. Acetate was utilized by M. barkeri in coculture with A. cellulolyticus after a lag period, whereas ethanol was metabolized by the sulfate reducer only under conditions of low H(2) partial pressure, i.e., when cocultured with A. celluloyticus-M. barkeri or when grown together with the methanogen. Only the three-component culture carried out the rapid conversion of cellulose to CO(2) and methane. Furthermore, this culture hydrolyzed the most cellulose-85% of that initially present. This amount was increased to 90% by increasing the population of M. barkeri in the triculture. Methane production was also increased, and a quicker fermentation rate was achieved.

Journal Article↗

Reliability of a flushing questionnaire and the ethanol patch test in screening for inactive aldehyde dehydrogenase-2 and alcohol-related cancer risk.

Molecular epidemiology of esophageal and upper aerodigestive tract cancers revealed that alcohol is more carcinogenic in persons with inactive aldehyde dehydrogenase-2 (ALDH2) than in those with active ALDH2. A simple questionnaire has been developed to screen for the facial flushing that occurs in persons with inactive ALDH2 when they drink even a single glass of beer. In this study, 266 of 284 consecutive male Japanese clinic patients (age > or = 50 years) completed the flushing questionnaire, and 239 underwent the ethanol patch test (a cutaneous model for the flushing response). Blinded genotyping showed inactive ALDH2 for 94.4% (102 of 108) of subjects who reported always flushing (early in their drinking history or currently) and for 47.7% (21 of 44) of those who reported sometimes flushing, whereas 95.6% (109 of 114) of subjects reporting that they never exhibited facial flushing had active ALDH2. When all three categories of flushing (current always, former always, and sometimes) were collapsed into one, the questionnaire's sensitivity and specificity for identifying inactive ALDH2 were 96.1 and 79.0%, respectively, compared with 72.4 and 71.4% for the ethanol patch test. The results suggest the utility of this simple flushing questionnaire in daily practice, as well as large-scale studies to assess cancer risks associated with drinking and ALDH2 and for activities aimed at preventing alcohol-related cancer.

Aged↗

An ethanologenic yeast exhibiting unusual metabolism in the fermentation of lignocellulosic hexose sugars.

Three lignocellulosic substrate mixtures [liquid fraction of acid-catalyzed steam-exploded softwood, softwood spent sulfite liquor (SSL) and hardwood SSL] were separately fermented by the industrially employed SSL-adapted strain Tembec T1 and a natural galactose-assimilating isolate (Y-1528) of Saccharomyces cerevisiae to compare fermentative efficacy. Both strains were confirmed as S. cerevisiae via molecular genotyping. The performance of strain Y-1528 exceeded that of Tembec T1 on all three substrate mixtures, with complete hexose sugar consumption ranging from 10 to 18 h for Y-1528, vs 24 to 28 h for T1. Furthermore, Y-1528 consumed galactose prior to glucose and mannose, in contrast to Tembec T1, which exhibited catabolite repression of galactose metabolism. Ethanol yields were comparable regardless of the substrate utilized. Strains T1 and Y-1528 were also combined in mixed culture to determine the effects of integrating their distinct metabolic capabilities during defined hexose sugar and SSL fermentations. Sugar consumption in the defined mixture was accelerated, with complete exhaustion of hexose sugars occurring in just over 6 h. Galactose was consumed first, followed by glucose and mannose. Ethanol yields were slightly reduced relative to pure cultures of Y-1528, but normal growth kinetics was not impeded. Sugar consumption in the SSLs was also accelerated, with complete utilization of softwood- and hardwood-derived hexose sugars occurring in 6 and 8 h, respectively. Catabolite repression was absent in both SSL fermentations.

Cellulose↗

Glial-derived neurotrophic factor (GDNF) prevents ethanol-induced apoptosis and JUN kinase phosphorylation.

Ethanol exposure during neural development leads to substantial neuronal loss in multiple brain regions. Our previous research indicated that exogenous glial-derived neurotrophic factor (GDNF) attenuated ethanol-induced cerebellar Purkinje cell loss. Additionally, ethanol decreased GDNF release suggesting that ethanol disrupts GDNF-signaling pathways. The present experiments utilized a homogeneous GDNF-responsive neuroblastoma cell line (SK-N-SH) to test the hypothesis that exogenous GDNF could attenuate ethanol-induced cell loss by suppressing cytotoxic signaling pathways and cell suicide. We measured two independently regulated markers of apoptosis, DNA fragmentation and the externalization of phosphatidylserine to the outer cell membrane leaflet. Ethanol induced a dose-related increase in both apoptosis and necrosis. Lower concentrations of ethanol (34 and 68 mM) specifically increased DNA fragmentation, while all concentrations (up to 137 mM) increased phosphatidylserine translocation, suggesting that ethanol induction of apoptosis is not a unitary process. Furthermore, only higher concentrations of ethanol (103 and 137 mM) induced necrosis. Additionally, ethanol specifically induced phosphorylation of c-jun N-terminal-kinase (JNK), a mitogen-activated protein (MAP) kinase selectively associated with apoptosis. In contrast, ethanol did not alter the phosphorylation of another MAP kinase, the extracellular signal-regulated kinases (ERK) that mediate cell survival. Thus, ethanol activated specific intracellular cell death-associated pathways and induced cell death. GDNF, in turn, prevented both ethanol-induced apoptosis and the activation of the death-associated JNK cascade. Therefore, GDNF may regulate multiple pathways to prevent ethanol-induced cell loss.

Annexin A5↗

Salt accumulation resulting from base added for pH control, and not ethanol, limits growth of Thermoanaerobacteriumthermosaccharolyticum HG-8 at elevated feed xylose concentrations in continuous culture.

Thermoanaerobacter thermosaccharolyticum HG-8 was grown in continuous culture to characterize growth limitation at high feed substrate and product concentrations. Continuous fermentation of 50 and 73 g/L xylose at a dilution rate based on the feed flow, D(f), of 0.053 h(-)(1) and with the pH controlled at 7.0 by addition of KOH resulted in steady state utilization of >99% of the xylose fed and production of ethanol and acetic acid at a mass ratio of about 2:1. Continuous cultures of T. thermosaccharolyticum growing at D(f) = 0.053 h(-)(1) achieved complete utilization of 75 g/L xylose in the presence of 19.1 g/L K(+) (0.49 M) and an ethanol concentration of 22.4 g/L ethanol. When the feed to a culture initially at steady state with a 75 g/L xylose feed and D(f) = 0.053 h(-)(1) was increased to 87.5 g/L xylose, limitation of growth and xylose utilization was observed. This limitation was not relieved by repeating this feed upshift experiment in the presence of increased nutrient levels and was not reproduced by addition of ethanol to a steady-state culture fed with 75 g/L xylose. By contrast, addition of KCl to a steady-state culture fed with 75 g/L xylose reproduced the K(+) concentration, limitation of growth and xylose utilization, and product concentration profiles observed in the feed upshift experiment. The maximum concentration at which growth of batch cultures was observed was 0.43 M for KCl, NaCl, and equimolar mixtures of these salts, suggesting that the observed limitation is not ion-specific. These data support the interpretation that inhibition salt accumulation resulting from addition of KOH for pH control is the limiting factor manifested in the feed upshift experiment and that both nutrient limitation and ethanol inhibition played little or no role as limiting factors. More generally, salt inhibition would appear to be a possible explanation for the discrepancy between the tolerance to added ethanol and the maximum concentration of produced ethanol reported in the literature for fermentation studies involving thermophilic bacteria.

Bacteria, Anaerobic↗

Effect of colchicine on lactate production by isolated hepatocytes in rats treated with carbon tetrachloride and ethanol.

This study was designed to evaluate the lactate production by isolated hepatocytes in rats with cirrhosis induced by means CCl4 + ethanol and the effect of colchicine in this experimental model of fibrosis. The effect of colchicine on lactate metabolism may be important in explaining the beneficial mechanism of this therapy on liver cirrhosis. Colchicine treatment produced a decrease in perivenular fibrosis and a descense in the degrees of this histological lesion. Colchicine treatment ameliorated the subsequent further development of cirrhosis. Lactate production in colchicine groups were higher than the carbon tetrachloride groups. By contrast, a priori, we observed a decrease in lactacidaemia and a lesser lactate utilization in colchicine groups comparison with CCl4 + ethanol groups. Our results suggest that colchicine improves the fibrosis by a mechanism independent of hepatic lactate metabolism.

Animals↗

Optimization of ethanol production from starch by an amylolytic nuclear petite Saccharomyces cerevisiae strain.

Ethanol fermentation characteristics of the 100% respiratory-deficient nuclear petite amylolytic Saccharomyces cerevisiae NPB-G strain was investigated in both shake-flask and controlled bioreactor cultivation conditions, and comparison with the earlier reported results revealed 54.6% increase in ethanol yield. Efforts to improve the starch utilization rate by increasing the selection pressure or supplying the fermentation medium with glucose did not prevent the observed decrease in time-dependent amylolytic activity. Response surface methodology (RSM) was then used as a statistical tool to optimize the initial yeast extract and starch contents of the medium, which resulted in a substantial increase in the stability of the expression plasmid in both the respiratory-deficient NPB-G and the parental respiratory-sufficient WTPB-G strains, with concomitant improvement in their amylolytic potentials. High ethanol yields on substrate values of the bioreactor cultures, which were very close to the theoretical yield, indicated that the amylolytic respiratory-deficient NPB-G strain was effective in the direct fermentation of starch into ethanol.

Biomass↗

Spontaneous recovery from ethanol-induced male infertility.

Chronic ethanol ingestion by the male is associated with reproductive impairment. No longitudinal studies have been carried out to determine the recovery of ethanol-related reproductive failure subsequent to moderate periods of abstinence. An animal model (C57B1 mouse) was utilized to examine the effectiveness of abstinence for reversal of ethanol-induced reproductive failure. After treatment with either a 5% ethanol diet (10 weeks) or a 6% ethanol diet (5 weeks), animals were hemicastrated (right testis and accessory organs); their reproductive tracts and epididymal spermatozoa were examined. Ingestion of the 5% and 6% ethanol diets resulted in significantly (p less than 0.05) decreased testicular weights (24% and 28%, respectively) and seminal vesicle/prostate weights (20%, 6% diet only), increased frequencies of germ cell desquamation (480% and 400%), inactive seminiferous tubules (186% and 567%) and inhibition of in vitro fertilization of mouse oocytes by epididymal spermatozoa (26% and 62%), as compared to their respective pair-fed control values. Also observed was a significant decrease in total motile spermatozoa (85%, 6% diet only). Improvement in all parameters was observed in the contralateral reproductive organs subsequent to ten weeks abstinence. Only germ cell desquamation remained significantly elevated (100% as compared to control) in animals that ingested the 5% diet. In contrast, significant abnormalities persisted ten weeks after treatment with the 6% ethanol diet, including increased germ cell desquamation (200%) and inactive seminiferous tubules (157%); decreased forward progression (17%) of epididymal sperm also persisted. If these data can be applied clinically, male alcoholic patients with reproductive disorders could have a prognosis of at least partial recovery following moderate periods of abstinence from ethanol.

Animals↗

Partial reversal of ethanol-induced male reproductive pathology following abstinence.

To date, no longitudinal studies have been carried out to determine the recovery of ethanol-related reproductive failure subsequent to moderate periods of abstinence. An animal model (C57B1 mouse) was utilized to examine the effectiveness of abstinence for reversal of ethanol-induced reproductive failure. After treatment with either a 5% (v/v) ethanol diet (10 weeks) or a 6% (v/v) ethanol diet (5 weeks), ethanol-treated animals and their pair-fed controls were electroejaculated and hemicastrated (right testis and accessory organs); their reproductive tracts and epididymal spermatozoa were examined. Ingestion of the 5% and 6% ethanol diets resulted in significantly (P less than 0.05) decreased weights of testes (24% and 28%, respectively) and seminal vesicles/prostate (20%, 6% diet only), increased frequencies of germ cell desquamation (480% and 400%), inactive seminiferous tubules (186% and 567%), sperm dysmorphology (31% and 119%) and inhibition of in vitro fertilization of mouse oocytes by epididymal spermatozoa (26% and 62%), as compared to their respective pair-fed control values. Also observed were significant decreases in epididymal sperm content (72%, 6% diet only), total motile spermatozoa (85%, 6% diet only) and seminal vesicles epithelial cell height (13% and 29%). No abnormal semen parameters were observed after treatment with the 5% ethanol diet; however, in animals treated with the 6% diet, significant decreases were noted in coagulum weight (50%), sperm count (85%) and acid phosphatase content (53%). Improvement in all parameters was observed in the contralateral half of the reproductive tract subsequent to 10 weeks abstinence. Only germ cell desquamation remained significantly elevated (100% as compared to control) in animals that ingested the 5% diet. In contrast, significant abnormalities persisting 10 weeks after treatment with the 6% ethanol diet included increased germ cell desquamation (200%), inactive seminiferous tubules (157%) and sperm dysmorphology (39%) and decreased forward progression (17%) of epididymal sperm, as compared to values. These findings are discussed in relation to the influence of alcohol consumption on male reproductive function in man.

Animals↗

Direct measurement of alcohol and its metabolites.

BACKGROUND: Ethanol can be easily and accurately measured in body fluids or vapours by several chemical and enzymatic methods. However, the persistence of ethanol in the body is short lived and ethanol's metabolism and distribution within the body are extremely complex. AIM: This article discusses the complex pharmacokinetics of ethanol and how pharmacokinetics can affect measured ethanol concentrations when ethanol is sampled across different individuals or from different body fluids or vapors, such as whole blood, plasma, breath, urine, saliva, or transdermal ethanol. FINDINGS: Several physical methods for the quantification of ethanol concentrations are described, including gas chromatography, electrochemical detection, infrared detection and enzymatic methods, along with their advantages and limitations. Also discussed, is the utility of the measurement of several immediate metabolites of ethanol, including acetaldehyde. acetate, and fatty acid ethyl esters. CONCLUSIONS: The complex distribution and metabolism of ethanol and its metabolites can obscure the relationship between the ethanol concentration that is measured in body fluids or vapours and the amount of ethanol that is actually taken into the body.

Alcohol Drinking↗