Interaction between ethanol metabolism and mixed-function oxidation in alcohol dehydrogenase positive and negative deermice.

To assess the effect of non alcohol dehydrogenase (ADH) ethanol metabolism on mixed-function oxidation, aminopyrine demethylation was studied in vivo and in vitro in deermice having normal liver ADH (ADH+) or lacking it (ADH-), in the presence and absence of ethanol. When injected 15 min prior to administration of [14C]aminopyrine, ethanol reduced the 14CO2 exhalation rate in both ADH- and ADH+ deermice. The inhibitory effect of ethanol was dose dependent in both strains, and there was no significant difference between strains. Chronic ethanol feeding increased 14CO2 production from [14C]aminopyrine in both animal strains (ADH- alcohol 5.9 +/- 1.3 vs ADH- control 2.9 +/- 0.03, P less than 0.025; ADH+ alcohol 5.9 +/- 0.3 vs ADH+ control 2.7 +/- 1.3 nmoles aminopyrine/100 g body wt/min, P less than 0.001). Alcohol feeding also induced aminopyrine N-demethylase activity measured in vitro. This induction was more pronounced in ADH- deermice. Ethanol also inhibited aminopyrine demethylation in liver homogenates from ADH- and ADH+ animals in a dose-dependent manner and to a comparable degree in both strains. The kinetics of aminopyrine N-demethylase inhibition by ethanol was competitive in the microsomal fraction from ADH- as well as ADH+ animals. These results suggest that inhibition of mixed-function oxidation by ethanol may be due to an effect of ethanol on the hepatic microsomes rather than to redox changes produced by ADH-mediated ethanol oxidation. Further, chronic ethanol feeding increased microsomal aminopyrine demethylation independently of the presence of ADH.

Assessment of the role of non-ADH ethanol oxidation in vivo and in hepatocytes from deermice.

Deermice genetically lacking alcohol dehydrogenase (ADH-) were used to quantitate the effect of 4-methylpyrazole (4-MP) on non-ADH pathways in hepatocytes and in vivo. Although primarily an inhibitor of ADH, 4-methylpyrazole was also found to inhibit competitively the activity of the microsomal ethanol-oxidizing system (MEOS) in deermouse liver microsomes. The degree of 4-MP inhibition in ADH- deermice then served to correct for the effect of 4-MP on non-ADH pathways in deermice having ADH (ADH+). In ADH+ hepatocytes, the percent contributions of non-ADH pathways were calculated to be 28% at 10 mM and 52% at 50 mM ethanol. When a similar correction was applied to in vivo ethanol clearance rates in ADH+ deermice, non-ADH pathways were found to contribute 42% below 10 mM and 63% at 40-70 mM blood ethanol. The catalase inhibitor 3-amino-1,2,4-triazole, while reducing catalase-mediated peroxidation of ethanol by 83-94%, had only a slight effect on blood ethanol clearance at ethanol concentrations below 10 mM, and no effect at all at 40-70 mM ethanol. These results indicate that non-ADH pathways (primarily MEOS) play a significant role in ethanol oxidation in vivo and in hepatocytes in vitro.

A new approach for evaluating circadian blood pressure levels and variability from 24 h ambulatory blood pressure profiles.

In 24 h blood pressure monitoring the severity of arterial hypertension is generally classified on the basis of the arithmetic mean of the diastolic blood pressure between 6 AM and 10 PM. In the present study Fourier analysis was used for evaluation of circadian blood pressure level and variability. A common reference profile was calculated on the basis of a group of 50 normotensive profiles. This reference profile is characterized by the fact that the sum of the squares of the distances between the individual profiles and the reference profile is a minimum. The individual 24 h profiles of 103 patients with untreated arterial hypertension were also each described by a Fourier series and were then compared with the normotensive reference profile. The comparison was made not only with respect to the absolute pressure over 24 h but also with respect to the circadian fluctuations in blood pressure. Our results show that the Fourier analysis of 24 h blood pressure profiles presented here can be used for more precise evaluation of 24 h blood pressure profiles.

Effect of CO2-induced hyperventilation on carbon tetrachloride (CCl4) levels following acute CCl4 poisoning.

To study under standardized experimental conditions the effect of a CO2-induced hyperventilation therapy on carbon tetrachloride (CCl4) levels following acute CCl4 poisoning, rats received 2.5 ml CCl4/kg BW by gastric intubation and were subsequently either treated by CO2-induced hyperventilation or kept in an atmosphere containing air. Peak levels of CCl4 were observed in the fat, liver and blood 3-6 h after the intoxication and were found to be considerably lower in animals treated by CO2-induced hyperventilation compared to their respective controls. These data therefore strongly support the efficacy of the CO2-induced hyperventilation therapy for CCl4 intoxication.

Quantitative assessment of carbon tetrachloride levels in human blood by head-space gas chromatography: application in a case of suicidal carbon tetrachloride intoxication.

A head-space gas chromatographic method for the determination of carbon tetrachloride in human blood is described. Standard samples with 0.5 ml whole blood containing different concentrations of CCl4 were analyzed at column temperatures ranging from 50 degrees to 90 degrees C. Advantages of this method include high sensitivity, simplicity in handling, rapid achievement of reliable results, accuracy and low costs. The practicability of this analytical method was studied in a patient following suicidal oral ingestion of a lethal dose of carbon tetrachloride.

A multicenter, randomized, double-blind, placebo-controlled, two-year trial to study the effect of nitrendipine on chronic renal transplant function.

The ongoing multicenter, randomized, double-blind, placebo-controlled trial investigates the effect of nitrendipine on kidney function after renal transplantation. Renal transplant recipients (6th-12th postoperative week, serum creatinine < 3 mg/dl) were divided into a normotensive (diastolic blood pressure < 90 mmHg) and a hypertensive group (diastolic blood pressure > or = 90, < 115 mmHg). Normotensive patients are randomly treated for 104 weeks with nitrendipine 2 x 5 mg daily or placebo, hypertensive patients with 2 x 10 mg - 2 x 20 mg nitrendipine daily or placebo and in case of inefficacy with additional antihypertensive drugs. Primary end point of the study is the renal transplant function. The trial was started in June 1990. One hundred and eight patients were included into the normotensive and 138 patients into the hypertensive group. Renal allograft function, cyclosporine trough levels and the donor characteristics were not different between the normotensive and hypertensive groups at entry into the study. After 12 months there was no significant change of renal transplant function in both groups. Cyclosporine trough levels were also similar in the normotensive and hypertensive group after 12 months. As expected, blood pressure decreased significantly after 12 months from 150 +/- 17/95 +/- 11 mmHg to 141 +/- 16/90 +/- 9 mmHg in the hypertensive group (p < 0.01). In contrast, in the normotensive group blood pressure increased significantly from 128 +/- 12/80 +/- 6 mmHg to 135 +/- 15/86 +/- 8 mmHg (p < 0.001). No normotensive but 4 hypertensive patients developed graft failure during the first 12 months of the study.

Effects of acute ethanol administration and chronic ethanol feeding on mixed function oxidation in deermice lacking ADH.

Hepatic microsomes catalyze the oxidation of ethanol and other drugs. The mechanisms through which ethanol alters mixed function oxidation are still debated. There is evidence that ethanol and drugs interact at a microsomal level, but there are also claims that ethanol may interfere with drug metabolism indirectly by affecting the supply of NADPH through NADH production in the ADH pathway. To investigate the role of chronic ethanol consumption, deermice with normal liver ADH (ADH+) or genetically lacking ADH (ADH-) were pair-fed liquid diets containing ethanol or isocaloric carbohydrate for 23 days. The acute effects of ethanol were studied in deermice fed standard laboratory chow and tap water ad lib. In vivo and in vitro, the effects of an acute dose of ethanol and chronic ethanol feeding on mixed function oxidation as measured by the demethylation of aminopyrine were similar in both animal strains. Statistical analysis showed no significant differences between ADH+ and ADH- animals under all experimental conditions studied. We conclude that induction and inhibition of mixed function oxidation by ethanol may be related to the interaction of ethanol with hepatic microsomes rather than to redox changes produced by ADH mediated ethanol metabolism.

Acute and chronic effects of nitrendipine in patients with precapillary pulmonary hypertension due to pulmonary fibrosis.

Eleven patients with histologically confirmed fibrosis of the lung were investigated for the effects of the dihydropyridine calcium antagonist nitrendipine on pulmonary hemodynamics. After 5 mg of acute sublingual nitrendipine, mean pulmonary artery pressure was significantly lowered (p less than or equal to 0.05) from 32 +/- 3 to 29 +/- 3 mmHg at rest, and significantly lowered (p less than or equal to 0.05) during exercise from 55 +/- 4 to 49 +/- 4 mmHg. Short-term oxygen application at rest significantly reduced this parameter to 28 +/- 3 mmHg (p less than or equal to 0.001). Nitrendipine lowered total pulmonary vascular resistance during both rest (from 412 +/- 50 to 351 +/- 49 dyn.s.cm-5; p less than or equal to 0.05), although it did not affect pulmonary arteriolar resistance. Also, oxygen treatment at rest influenced only total pulmonary vascular resistance (reduction from 412 +/- 50 to 373 +/- 48 dyn.s.cm-5; p less than or equal to 0.01), but not pulmonary arteriolar resistance. Pressure-flow curves, which were derived from cardiac output at rest and during exercise and from the corresponding gradient between mean pulmonary artery pressure and pulmonary capillary wedge pressure, remained unchanged by acute medication. Since a change in arterial oxygen partial pressure was not noticed after nitrendipine, arteriovenous shunting or a worsening of ventilation perfusion relationships can be excluded. Long-term (3 weeks) treatment (double-blind parallel design) with 10 mg of nitrendipine (4 patients) once daily showed no advantage in comparison to placebo (6 patients).(ABSTRACT TRUNCATED AT 250 WORDS)

Decreased hepatotoxicity of dimethylnitrosamine (DMN) following chronic alcohol consumption.

Compared to controls receiving physiological saline, the i.p. administration of dimethylnitrosamine (DMN) on 5 consecutive days to rats fed a nutritionally adequate liquid diet resulted 24 hours after the last injection of significant increases in glutamic dehydrogenase (GDH), glutamic oxylacetate transaminase (GOT), and glutamic pyruvate transaminase (GPT) activities in the serum, indicating a striking hepatotoxic effect of this compound. This was confirmed by the histological demonstration of massive centrolobular necrosis. Conversely, following pretreatment of the rats with an ethanol containing liquid diet for 23 days and subsequent administration of DMN the increases of serum enzyme activities and massive centrolobular necrosis could not be observed. These results therefore suggest that chronic alcohol consumption protects from hepatotoxicity due to DMN, most probably due to an enhancement of detoxifying pathways of the parent component or one of its toxic metabolites.

[The biochemistry of alcohol metabolism]. / Biochemie des Alkoholmetabolismus.

The metabolism of ethanol to acetaldehyde in the liver proceeds via alcohol dehydrogenase (ADH) and the microsomal ethanol-oxidizing system (MOS), whereas catalase plays no significant role. ADH is an enzyme of the cytosol, requires NAD+ as cofactor and exhibits a pH optimum in the alkaline range. The Km of ADH is about 2 mM for ethanol (equivalent to 0.1%). Thus, the enzyme is already saturated at low ethanol concentrations. Conversely, MEOS resides in the endoplasmic reticulum, requires NADPH and O2, is inhibited by CO and exhibits a km of about 10 mM corresponding to 0.5% ethanol. This enzyme system is therefore primarily the pathway of ethanol metabolism at intermediate to high ethanol concentrations. MEOS has many properties in common with other drug metabolizing enzymes and is characterized by inducibility following chronic ethanol consumption, which suggests the involvement of the microsomal system in the adaptive enhancement of ethanol clearance commonly observed in alcoholics. The product of ethanol oxidation by ADH, MEOS and catalase is acetaldehyde. Acetaldehyde is oxidized in the liver to acetate by NAD dependent aldehyde dehydrogenase. Four isozymes have been identified. Lack of isozyme I is responsible for the "flush-syndrome" commonly observed in asian people following alcohol intake. Ethanol metabolism is affected by the aging process and is decreased with advancing age.

[The liver and alcohol]. / Leber und Alkohol.

The liver is the main organ for alcohol metabolism and is therefore predisposed for various functional changes and irreversible alterations. The alcoholic fatty liver represents the early stage of alcohol-induced liver diseases and is completely reversible upon consequent alcohol abstinence. Already at this early stage a significant increase of gamma-glutamyltransferase activities is commonly found in the serum, which can mainly be attributed to an enzyme induction in the endoplasmic reticulum of the liver cell. Other stages of alcohol-induced liver diseases include the alcoholic hepatitis and the liver cirrhosis, which have a better prognosis upon consequent alcohol abstinence compared to continuous alcohol consumption. Many therapeutic studies with various drugs have been carried out in patients with alcohol-induced liver diseases, but at present a treatment with drugs in a sufficiently great number of patients has not been firmly established. The most important medical goal is to establish the diagnosis of alcohol-induced liver diseases already at the early stage of the fatty liver in order to initiate the necessary therapeutic measures with the aim of a consequent alcohol abstinence.

[Toxic and metabolic liver injury (author's transl)]. / Toxische Leberschäden.

Water soluble exogenous compounds are commonly excreted by the kidneys, but most of the exogenous substances are lipid soluble and have therefore first to be metabolized in the liver to water soluble compounds. Depending upon the nature of the chemical compound, the metabolism in the liver leads either to detoxification or toxification. Alcohol belongs to the most important substances which may cause severe liver injury. Alterations of the liver due to hydrocarbons as well as carcinogens, mycotoxins and thorium dioxide are relatively rare. Compounds such as analgesic and antiarrhythmic drugs, antibiotics, oral antidiabetic agents, antihypertensive and antirheumatic agents, chemotherapeutic drugs, hormones, laxatives, psychotropic drugs, thyreostatic and antineoplastic agents may also cause liver injury. For establishing the diagnosis, a detailed past history is required especially with respect to alcohol and drug consumption as well as regarding occupational exposure towards toxic compounds. Although the determination of liver enzyme activities in the serum may give some indication for liver cell injury, the histological examination of the liver by needle biopsy is required for the diagnosis. The therapy consists of the exclusion of the toxic compound and, if possible, of an increased elimination of the ingested toxins.

Effect of ethanol on carbon tetrachloride levels and hepatotoxicity after acute carbon tetrachloride poisoning.

To study the effect of an acute dose of ethanol on carbon tetrachloride (CCl4) concentration and hepatotoxicity, female rats received ethanol (2.5 ml/kg body wt.) either intragastrically or intraperitoneally following intragastric administration of CCl4 (1.5 ml/kg body wt.). Three hours after acute CCl4 intoxication there was a striking increase in CCl4 concentration in animals treated simultaneously with ethanol intragastrically compared to those receiving ethanol intraperitoneally. This increase was significant (P less than 0.05) and amounted to 211% for blood, 236% for liver and 405% for fat tissue, whereas animals treated with CCl4 alone showed CCl4 concentrations in the range between the two other experimental groups. Serum activities of glutamate oxalacetate transaminase, glutamate pyruvate transaminase and glutamate dehydrogenase were found to be considerably higher in animals treated with the combination of CCl4 and ethanol when compared to those receiving CCl4 alone, showing that ethanol given intraperitoneally or intragastrically enhances CCl4 hepatotoxicity. Since the intraperitoneal administration of ethanol led to a reduction rather than an increase in CCl4 concentration in the early phase of intoxication, additional mechanisms independent of actual levels of CCl4, such as direct effects of ethanol on the CCl4 metabolizing enzyme of the membrane of the endoplasmic reticulum, have to be implicated in the pathogenesis of the potentiation of CCl4 hepatotoxicity by ethanol.

Calcium antagonists and renal protection.

A growing body of evidence supports the notion that calcium antagonists exert a renal protective effect. Calcium antagonists may play an important future role in renal hemodynamics related to their reversal of renal vasoconstrictors. Calcium antagonists are also capable of blocking intracellular calcium overload induced by various types of ischemia or toxic stimuli. Features such as these may be of substantial value in ameliorating acute renal insufficiency secondary to renal ischemia, iodinated radiographic contrast media, or the administration of various nephrotoxic drugs. The latter includes agents such as the aminoglycoside antibiotics, cyclosporine A, and the cancer chemotherapeutic agent cisplatin. Recent prospective, controlled studies from our group indicate that calcium antagonists protected against postischemic acute renal failure in the setting of cadaveric renal transplantation. Moreover, in a prospective, randomized, controlled clinical trial, we were able to demonstrate that the prophylactic use of nitrendipine reduced the decrease in GFR in patients receiving radiographic contrast agents. Such protection may extend to favorably influencing the course of chronic renal insufficiency, particularly when the latter is complicated by hypertension. Seven putative mechanisms have been proposed by which calcium antagonists may ameliorate the decline in GFR associated with renal insufficiency. These are: (a) reduction in blood pressure per se, (b) reduction in renal hypertrophy, (c) modulation of mesangial traffic of macromolecules, (d) reduction in metabolic activity in remnant renal tissue, (e) amelioration of uremic nephrocalcinosis, (f) reduction of pressure-induced calcium entry into vessel walls, and (g) reduction of free radical formation. Experimental investigations in rats with reduced renal mass, desoxycorticosterone-induced hypertension, or chronic angiotensin II infusion, and in spontaneously hypertensive rats support such a view.

Protective effect of CO2-induced hyperventilation on the hepatotoxicity elicited by carbon tetrachloride.

Following oral intake or inhalation, halogenated hydrocarbons are metabolized to hepatotoxic intermediates in the liver to only a small extent, the major part being eliminated via the lungs without biochemical transformation. Following intoxication, increased pulmonary elimination of hydrocarbons can be achieved in patients by treatment with CO2-induced hyperventilation. To investigate the efficacy of this new therapy under exact experimental conditions, female Wistar rats received 2.5 ml CCl4/kg BW by gastric intubation and were then treated with CO2-induced hyperventilation. In comparison to untreated animals, hyperventilated rats showed only a few signs of hepatic injury by histological evaluation, whereas massive centrolobular necroses and fatty infiltrations were observed in non-hyperventilated animals. By biochemical assessment, significant decreases of GOT, GPT and GDH activity were observed in the serum, when hyperventilated rats were compared to untreated animals. Moreover, the LD50 for CCl4 was almost trebled after hyperventilation compared to the non-hyperventilated animals. The increased LD50, and the biochemical and histological results therefore substantiate the usefulness of CO2-induced hyperventilation therapy in the treatment of intoxications by hydrocarbons under standardized experimental conditions.

[Ambulatory blood pressure monitoring: significance of blood pressure variability for progression of heart hypertrophy]. / Ambulantes Blutdruckmonitoring: Bedeutung der Blutdruckvariabilität für die Progression einer Herzhypertrophie.

It is known that ambulatory blood-pressure monitoring gives a better prediction of target organ damage and prognosis than clinical blood pressure. Many studies have found a closer correlation for ambulatory blood pressure with left ventricular hypertrophy than clinical blood pressure. One question that is discussed controversely is whether the variability of blood pressure is also a determinant of target organ damage independent of the average level. In 52 patients with elevated casual blood pressure a 24-h ambulatory blood-pressure measurement (Space Labs 90202) was performed and left ventricular hypertrophy was evaluated by M-mode echocardiography. The following parameters of blood pressure variability were calculated from the profiles: the standard deviation of the mean value, the variation coefficient and the parameter of variability as proposed by Schächinger et al. Furthermore a Fourier analysis of the blood pressure data was performed to quantify blood pressure variability. We found no statistically significant correlation between blood pressure variability and left ventricular mass. However, systolic and diastolic blood pressure level showed a significant correlation with left ventricular hypertrophy (r = 0.45 and r = 0.49, p < 0.05). Thus, blood pressure variability as calculated from the ambulatory, non-invasive blood pressure monitoring is a poor predictor for secondary damage of the heart.

[Analysis of circadian blood pressure profiles using Fourier analysis]. / Analyse von zirkadianen Blutdruckprofilen mit Hilfe der Fourieranalyse.

Blood pressure is subject to considerable circadian and situational fluctuation. In 24-h blood-pressure monitoring the severity of arterial hypertension is generally classified on the basis of the arithmetic mean of the diastolic blood pressure between 07.00 and 22.00 hours. In the present study Fourier analysis was used to generate continuous functions from the discrete blood-pressure values measured during 24-h blood-pressure monitoring in a sample of 50 normotensive persons aged from 25 to 80 years. A common reference profile was then constructed from these 50 profiles. This reference profile is characterized by the fact that the sum of the integrals over the squares of the distances between the individual profiles and the reference profile is the smallest possible. The reference profile is thus the best approximation of all normotensive profiles and practically ignores individual blood pressure fluctuations. The individual 24-h profiles of 80 patients with untreated arterial hypertension were classified on the basis of the daytime mean as mild, moderate or severe arterial hypertension and also each is described by a Fourier series. The pathological profiles were then compared with the normotensive reference profile. The comparison was made, not only with respect to the absolute pressure over 24 h, but also with respect to the circadian fluctuations in blood pressure. Comparison of the profiles shows that the Fourier analysis of 24-h blood-pressure profiles presented here permits reliable analysis and classification of arterial hypertension and can thus be used for more precise evaluation of the influence of antihypertensives on 24-h blood-pressure profiles.