Ethanol-induced increase in procainamide acetylation in man

1 The effect of ethanol on procainamide pharmacokinetics was studied in humans by two different experimental designs. In one, ethanol was given 1.5 h after taking the drug followed by hourly drinks, while in the other ethanol was given 2 h before and subsequently after taking the drug. 2 In both studies, ethanol caused a significant reduction of T1/2 and a significant increase in total clearance of procainamide, while the apparent volume of distribution of procainamide, as well as the renal clearance of both procainamide and N-acetylprocainamide were unaffected by ethanol treatment. 3 Ethanol treatment increased the percentage of N-acetylprocainamide measured in blood and urine and the ratio of AUCNAPA/AUCPA significantly. 4 The T1/2 and total clearance of procainamide was significantly different in slow and rapid acetylators.

Effects of four restricted liquid diet regimens and one nonrestricted solid diet regimen on enzyme activities associated with hepatic drug metabolism

Two different nutritionally adequate liquid diets containing either 18% protein, 47% carbohydrate and 35% lipid, or 18% protein, 12% carbohydrate and 70% lipid were given to rats once daily or in four divided doses for 3 weeks. The liquid diets decreased hepatic protein content and concentration and the activities of hepatic gamma-glutamyl transferase and NADPH cytochrome c reductase, compared to a zero time group fed chow and water. There were no important differences between the treatment groups. Aniline hydroxylase activity was also decreased by the liquid diets, but the high-lipid diet decreased the activity significantly less than the high-carbohydrate diet. Rats fed chow and water ad libitum for 3 weeks were less different from the zero time value than rats in any of the liquid diet groups. The effects of liquid diets may be important in alcohol research, where a high-carbohydrate liquid diet in restricted amounts is being widely used for feeding the control animals.

Sulfonamide acetylation in isolated rabbit and rat liver cells

Suspensions of isolated liver cells were prepared from rabbit livers perfused with Ca++-free buffer and 0.05% collagenase. Primary cell suspensions (containing both parenchymal and non-parenchymal liver cells) metabolized sulfadimidine and sulfanilamide at first-order kinetics for at least 2-3 hrs. Suspensions of purified rabbit liver parenchymal cells had an equal metabolic capacity, and it could be demonstrated that the metabolic rate of both sufadimidine and sulfanilamide was correlated to the amount of viable parenchymal cells in suspension. Suspensions of non-parenchymal cells were lacking the ability to metabolize both drugs. By means of homogenates of purified rabbit and rat liver cells, it could be demonstrated that the enzyme N-acetyltransferase was located in the cytosolic fraction of the parenchymal cells. It was concluded that the cytosolic fraction of the liver parenchymal cells is the main site of sulfonamide acetylation in both rabbit and rat.

Partial separation and biochemical characteristics of periportal and perivenous hepatocytes from rat liver

Suspensions of enzymatically prepared hepatocytes from starved rats were separated according to their buoyant density at 12 degrees C in linear, isosmotic gradients of metrizamide, centrofuged at low speed for a relatively short time. The recovery of cell protein was 86%. Hepatocytes of high viability formed a single band around 1.10 g/cm3 and were recovered as four density populations (P1-P4) form low to high density, respectively. The content of protein was significantly lower in population P1, while the content of neutral fat or the averaged cell size was similar in the various populations. The specific activity of alanine aminotransferase increased in the order P1-P4. The distribution of this enzyme within the intact liver acinus obtained by others indicate that a partial separation of periportal and perivenous hepatocytes had occurred. The activity patterns of lactate dehydrogenase, glutamate dehydrogenase, isocitrate dehydrogenase (NADP+) and pyruvate kinase, also with known intra acinar distributions, supported this conclusion. The hepatocytes showed signs of shrinkage after separation, but since they retained a normal ultrastructure, most enzyme activities and viability, the present technique was regarded superior to previous procedures of hepatocyte separation by density. The degree of separation was calculated from an equation (see Appendix), and the periportal/perivenous ratio for parameters measured in density populations can be obtained. The specific activity of phosphofructokinase, alcohol dehydrogenase and aldehyde dehydrogenase showed no differences between populations. However, the ratio high-Km/low-Km aldehyde dehydrogenase increased in the order P4-P1.

Ether inhibition of ethanol metabolism in isolated rat liver parenchymal cells

The effect of diethyl ether on ethanol metabolism was studied in isolated rat hepatocytes and ether was found to inhibit ethanol oxidation in a dose-dependent manner. At ethanol concentrations of approximately 30 mM, diethyl ether inhibited ethanol oxidation by approximately 58%, 40%, and 20% at ether concentrations of 30, 20, and 10 mM, respectively. This inhibition was also seen at a low ethanol concentration (5.4 mM) and in pyruvate (5 mM)-stimulated hepatocytes which exhibited increased rates of ethanol metabolism closer to in vivo rates. Accumulation of acetaldehyde from ethanol in cyanamide (400 micron M)-treated hepatocyte suspensions was also reduced by approximately 16% by 30 mM ether. It was concluded that inhibition of ethanol metabolism by diethyl ether might be of practical importance in studies of ethanol metabolism in ether anesthetized animals.

Combined effects of ethanol and pH-change on protein synthesis in isolated rat hepatocytes

Rat liver parenchymal cells were isolated and incubated for 80 min. in buffered sale solutions. 14C-valine incorporation in the presence of a high concentration of unlabelled valine (4.2 mM) was taken as a measure of protein synthesis. The pH dependence of the synthesis of cell and medium proteins was studied at pH values varying from 6.6 to 7.9. The results showed that maximum protein synthesis occurred close to the physiological pH value. Protein synthesis was reduced at both lower and higher pH-values. Protein synthesis was inhibited by the addition of ethanol (30 mM). The relative inhibition caused by ethanol got more pronounced as the pH of the hepatocyte suspensions was lowered. The metabolism of ethanol resulted in lowering of the pH cell suspension. It is suggested that the depression of protein synthesis by ethanol could be mediated by the fall in pH due to ethanol metabolism.

Sulfonamide acetylation in isolated rat liver cells

Primary suspension of isolated liver cells, prepared from rat livers perfused with Ca++ free buffer and 0.05% collagenase, were used for studies of sulfadimidine uptake and metabolism at various temperatures (29 degrees -41 degrees) and pH (6.4 - 7.8). The intracellular: extracellular ratio for sulfanilamide was found to be insensitive to both temperature and pH variations, while the corresponding ratio for sulfadimidine was pH dependent but insensitive to temperature variation. Decreasing pH increased the cell content of sulfadimidine. Sulfanilamide was metabolized by acetylation only, while sulfadimidine gave rise to several metabolites. The rate of sulfanilamide acetylation in primary cell suspensions was of the same order of magnitude as the acetylation rate of sulfanilamide published previously for the intact organ. Sulfanilamide was acetylated at the highest rate in the pH-region from 7.0 to 7.5, while sulfadimidine was metabolized most rapidly between pH 6.7 and 7.3. At pH 7.5 sulfadimidine was metabolized at a rate only 35% of the rate at pH 7.3. The acetylation rate of both drugs increased with increasing temperature, approximately 5% per degree celcius, and exhibited a Q10 of 1.5.

Diethyl ether influence on the metabolism of antipyrine, paracetamol and sulphanilamide in isolated rat hepatocytes

Drug metabolism was studied in suspensions of isolated rat liver parenchymal cells. The influence of diethyl ether 2.5-30 mmol litre-1 on metabolism of antipyrine, paracetamol and sulphanilamide was studied. A dose-related ether inhibition of antipyrine and paracetamol metabolism was found. Fifty per cent inhibition of antipyrine metabolism occurred at ether concentrations between 2.5 and 5 mmol litre-1 while 50% inhibition of paracetamol metabolism was found at greater ether concentrations (20-30 mmol litre-1). No ether inhibition of sulphanilamide metabolism was demonstrated. It is concluded that different degrees of ether interaction have to be considered for the various hepatic pathways of drug metabolism.

Protein secretion in suspensions of isolated rat hepatocytes: no influence of acute ethanol administration

The effect of ethanol on the secretion of proteins was studied in hepatocytes isolated from 24-h fasted rats and from fed rats. Hepatocytes were isolated after collagenase disruption of the liver and incubated in a standard medium containing amino acids, bovine albumin, glucose, penicillin and streptomycin in HEPES buffer. Cell viability was determined by urea production and trypan blue exclusion. When studying protein export, a model had to be chosen in which the labeling is accomplished before the addition of the test agents. Cells were incubated with [3H]valine for 2.5 and 7.5 min followed by a 15-mM valine chase and the incubates were adjusted to final concentrations of ethanol of 50 mM, 100 mM, colchicine 5-50 microM or cycloheximide 18 microM. Cells and media were harvested at various times, and counts incorporated into medium and cell protein were determined. Cycloheximide inhibited protein synthesis by 99%, decreased protein secretion by 10-20%, but did not further inihibit protein labeling when given after the chase confirming the chase's effectiveness. Colchicine inhibited protein release by 27-54% depending on the dose. With control cells labeled protein and specifically albumin appeared in the medium 20 min from the start of the pulse and this release of protein was not inhibited by 50 mM or 100 mM ethanol incubated with cells from the same animal whether the donor has been fed or fasted. The values for the ethanol-treated cells ranged from 94.0 to 113% of the control values from 30 to 120 min after the addition of the pulse. Lactate levels were markedly elevated, and urea synthesis decreased in the presence of either 50 mM EtOH or 100 mM EtOH. Thus using a method that can distinguish the effect of ethanol on synthesis from secretion, it is concluded that acute exposure to EtOH does not interfere with protein secretion.

Hepatic microsomal drug metabolism, glutamyl transferase activity and in vivo antipyrine half-life in rats chronically fed an ethanol diet, a control diet and a chow diet

The effects of chronic consumption of ethanol on several hepatic enzyme activities were investigated. Male Wistar rats (180 g) were divided in three groups, two of which were pair-fed ethanol or control liquid diets while the third group received chow and water ad libitum (untreated group). The following changes were observed after 1 and/or 6 weeks when expressed per 100 g b.w.: In the ethanol group, the amount of cytochrome P-450 increased as did the activities of aniline hydroxylase and glutamyl transferase. The in vivo half-life of antipyrine decreased. The activity of NADPH cytochrome c reductase in the ethanol group was different from the reference groups, but not changed compared to pre-experimental values. The activities of ethylmorphine N-demethylase and aryl hydrocarbon hydroxylase were decreased when expressed per gram of microsomal protein. In the control group, the activity of NADPH cytochrome c reductase declined and so did hepatic weight. The study gave support to a suspicion that feeding control diet may influence hepatic enzyme activities as well as relative liver weight. This influence may magnify ethanol effects on NADPH cytochrome c reducdase and relative liver weight when such effects are measured as the difference between the control and the ethanol group at single points of time. In addition, our study showed that ethanol should not be regarded as a general inducer of microsomal enzymes.

Formation of acetaldehyde from diethyl ether in man

Diethyl ether anaesthesia caused detectable blood acetaldehyde levels in 15 patients. The average acetaldehyde concentration was 21 micro M which approximates the level found after intake of ethanol. No acetaldehyde could be found in patients anaesthetised without ether.

Inhibition of fracture healing by indomethacin in rats

The effect of indomethacin (2 mg/kg/day) on the healing of closed unimmobilized femoral fractures was examined in rats. A standard femoral fracture was produced in 205 male adolescent rats, and three different experiments were done. In a long-term experiment, the rats were treated with either indomethacin or placebo for 29 days and fracture healing followed for a maximum of 91 days. In two short-term experiments, the rats were treated with either indomethacin or placebo for a week and followed for a maximum of 122 days. The effect of age was studied in one experiment. Indomethacin plasma levels were about 1 microgram/ml in the indomethacin-treated animals. In the long-term experiment, indomethacin inhibited fracture healing (P less than 0.006) and increased the angulation between the femur fragments. In the short-term experiments indomethacin inhibited fracture healding (P less than 0.033) and increased the interfragmentary angle as well as fracture instability. All untreated fractures healed within 10 weeks in younger rats (210 g), whereas only 44% healed in older rats (295 g).

Changes in protein, RNA and DNA content in various rat organs after long-term intake of ethanol

Male Wistar rats were given ethanol (approximately 25% of total caloric intake), while two different control groups were pair-fed isocaloric amounts of lipids or sucrose. After 7--10 weeks the following organs were studied: liver, cerebrum, heart, diaphragm, kidneys and testes. In fasted, ethanol treated rats there was a reduction in the hepatic concentration of RNA and the cerebral RNA/DNA ratio, when compared to both control groups, while no effects were found with respect to organ weight and amounts of protein, RNA or DNA in heart, diaphragm, kidneys and testes. When fed, ethanol treated animals were compared to both control groups, no effects on organ weight and composition were found in any tissue studied. Several significant differences were registered in the ethanol group as compared to one control group only, as well as between the two control groups. The consumption of ethanol (25% of total calories) thus caused only minor alterations in gross organ composition. These results also indicate the importance of interpreting with care any apparent effect of ethanol ingestion, unless at least two different control groups have been employed.

Incorporation of labelled amino acids into proteins of isolated parenchymal and nonparenchymal rat liver cells in the absence and presence of ethanol

Parenchymal and nonparenchymal cells were isolated from perfused rat livers and incubated at 37 degrees C in the absence and presence of ethanol (50 mM). 1. Nonparenchymal cells prepared by means of centrifugation showed a higher rate of incorporation of L-[U-14C]valine into protein than nonparenchymal cells prepared by means of pronase. Cells prepared by the former method were used for further studies. 2. Protein degradation was present in suspensions of both parenchymal and nonparenchymal cells evidenced by increasing levels of branched amino acids in the intracellular and extracellular compartment during cell incubation. 3. The rate of cellular protein synthesis (corrected for precursor pool specific radioactivity) was of the same order of magnitude in nonparenchymal and parenchymal cells when expressed as nmol valine incorporated per mg protein. This rate was also close to the value found in intact liver by other workers. 4. Approximately 25% of the total radioactivity incorporated during incubation for 2 h was found in proteins released to the medium from parenchymal cells, while the corresponding figure for nonparenchymal cells was 3.5%. 5. Ethanol inhibited incorporation of labelled valine into stationary and medium proteins of parenchymal cells. No such effects were found in nonparenchymal cells. 6. Nonparenchymal cells did not metabolize ethanol while parenchymal cells did, shown by changes in lactate/pyruvate ratio and medium pH. It was concluded that nonparenchymal cells are capable of synthesizing proteins at a rate comparable to that found in parenchymal cells. Protein synthesis in parenchymal cells was inhibited by ethanol, but nonparenchymal protein synthesis was unaffected. This difference may be linked to the ability of the former cell type to metabolize ethanol.

Ethanol-induced increase in drug acetylation in man and isolated rat liver cells

Sixteen healthy volunteers took part in a cross-over study examining the effect of ethanol on the rate of sulphadimidine acetylation (blood ethanol concentration about 1 g/1). In both rapid and slow acetylators the apparent half life of the drug decreased by about 20% after ethanol (mean reduction 39 +/- SE 8 min) and the amount of drug acetylated, measured in blood and urine, increased. In three slow acetylators the rate of acetylation in blood increased so noticeably after ethanol that they would otherwise have been classified as rapid acetylators. Suspensions of isolated rat liver cells showed an increase of about 30% in the rate of sulphadimidine acetylation after the addition of ethanol (2 g/1). Patients' usual alcohol consumption should be taken into account in determining their acetylator status.

Is moderate ethanol consumption teratogenic in the rat?

Female Wistar rats were given ethanol in their drinking fluid to cover 20-25% of the total calories consumed for 3-4 weeks prior to, during and also after pregnancy in some experiments. Soya oil was substituted for ethanol isocalorically in the control groups. Apart from a statistically significant reduction in litter size based on the number of apparent normal foetuses at intrauterine examination, no significant changes in reproductive performance could be recorded after ethanol treatment. In the offspring, examined up to 24 days of age, the body and some viscera weights were statistically significantly higher at some stages from 2 to 14 days. The general trend, however, showed that there were no significant differences in body, brain, liver, kidney, and heart muscle weights between control and ethanol offspring measured in rats between 0 and 24 days of age. Two gross malformations were recorded among 321 pups of ethanol treated mothers, whereas no malformations were found in 444 control pups. It was concluded that moderate ethanol consumption by rat mothers for 3-4 weeks before and during pregnancy as well as during the suckling period, had no serious effects on their reproductive performance and the development of their offspring measured by the parameters used in the present investigation.

Activity of alcohol dehydrogenase and acetaldehyde dehydrogenases in the liver and placenta during the development of the rat

The ontogenetic development of the enzymes alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenases (ALDH I and II) was followed in rats. ADH could be detected just before birth and increased gradually to reach 82% of adult values at 47 days. ALDH I and II were present from day 15 of gestation, increased rapidly at birth, and reached 80-90% adult values at 47 days. The ratio between ALDH and ADH activities decreased gradually during ontogenesis. The relative subcellular distribution of all enzymes was identical before birth, 7 days after birth and in adults. The placental activities of ADH and ALDH I and II were studied at 15 and 20 days of pregnancy. ADH could not be detected in placentas. Low activities of ALDH I and II were present in placentas studied at 15 days of gestation, and still lower activities were found in placenta at 20 days.

Induction of tryptophan oxygenase by dexamethasone in isolated hepatocytes. Dependence on composition of medium and pH

Hepatocytes were isolated from perfused rat livers. 4 x 10-6 cells/ml were incubated at at 37 degrees C in different media in the absence and presence of a steroid hormone, dexamethasone phosphate (2 x 10-5 M). 1. Hormonal enzyme induction occurred in cells suspended in a simple salt medium, devoid of amino acids and macromolecules. This induction was completely blocked by addition of either actinomycin D (2 mu-g/ml) or cycloheximide (50 mu-g/ml). 2. Incubation of cells in media containing defatted albumin did not enhance hormonal enzyme induction, although disintegration of cells during incubation was reduced. Addition of a crude albumin fraction reduced tryptophan oxygenase induction and dextran completely blocked enzyme induction by dexamethasone. 3. An increase of dexamethasone concentration in the presence of albumin to 9 x 10-5 M was unable to raise enzyme induction further, and a still higher concentration of hormone, 3 x 10-4 M, resulted in reduced enzyme induction. 4. The hormonal induction of tryptophan oxygenase was most pronounced when the pH of the medium was between 7.0 and 7.6, with an optium at 7.3. No induction was found when the pH of the medium was either 6.6 or 7.8. The basal tryptophan oxygenase activity was much less influenced by similar pH variations. It is concluded that hepatocytes in suspension are able to carry out hormone-stimulated enzyme synthesis and that factors influencing this process may be studied under controlled conditions in such systems.