Studies on the interaction between ethanol and serotonin metabolism in rat, using deuterated ethanol and 4-methylpyrazole

The metabolic interaction between ethanol and serotonin (5-hydroxytryptamine) via alcohol dehydrogenase (ADH; EC 1.1.1.1) was studied in tissue homogenates of Sprague-Dawley rats by following the transfer of deuterium from deuterated ethanol over endogenous NADH to 5-hydroxytryptophol (5HTOL). Homogenates of whole brain, lung, spleen, kidney, liver, stomach, jejunum, ileum, colon, and caecum were incubated in the presence of [2H2]ethanol and 5-hydroxyindole-3-acetaldehyde (5HIAL), and the [2H]5HTOL formed was identified and quantified using gas chromatography-mass spectrometry. ADH activity was most abundant in liver, kidney, and within the gastrointestinal tract. The highest incorporation of deuterium was obtained in homogenates of kidney, lung, and colon, whereas in brain, which contains very low ADH activity, no incorporation could be demonstrated. Addition of extra NAD+ (2.4 mM) increased the formation of [2H]5HTOL 2.6-fold in liver homogenates, but only 1.2-fold in kidney homogenates. 4-Methylpyrazole, a potent inhibitor of class I ADH, inhibited the 5HIAL reduction in homogenates of lung, kidney, jejunum, ileum, and colon, and caused a marked drop in 5HTOL oxidation in all tissues except stomach and spleen. These results demonstrate that in the rat a metabolic interaction between ethanol and serotonin via the ADH pathway may take place in several tissues besides the liver, which is the main tissue for ethanol detoxification.

Renal effects of amino acid infusion in cardiac surgery

OBJECTIVE

To evaluate effects of amino acids on renal function and oxygen consumption and the role of individual amino acids on renal blood flow (RBF) changes.

DESIGN

Prospective, randomized, controlled study.

SETTING

Operating room in cardiothoracic surgery department, university hospital.

PARTICIPANTS

Twenty-two male patients submitted to elective first-time coronary artery bypass surgery.

INTERVENTIONS

A catheter was placed in the left renal vein for thermodilution RBF measurements and blood sampling. In 11 patients, a balanced mixed amino acid infusion was infused (200 mL/hr) for 30 minutes immediately after the operation.

MEASUREMENTS AND MAIN RESULTS

RBF and glomerular filtration rate increased during amino acid infusion compared with the control group. Renal oxygen consumption increased in the amino acid group and correlated with the increase in RBF (r = 0.70, p<0.001). Amino acid infusion induced two- to fourfold increases in plasma concentrations of individual amino acid concentrations and promoted renal extraction of aspartate, glutamate, glycine, and histidine. No correlation was observed between arterial concentration or uptake of individual amino acids and RBF.

CONCLUSIONS

The increase in RBF from a mixed amino acid infusion was associated with increased glomerular filtration rate and renal consumption of oxygen. Changes in RBF of a mixed amino acid infusion could not be linked to plasma level or renal uptake of any individual amino acids.

The physiological basis for faster growth in the Sydney rock oyster, Saccostrea commercialis

Sydney rock oysters were sampled from a mass selection experiment for growth (the "selected" category) and from a control ("not selected") population and held in the laboratory at three ration levels. We evaluated three models to explain faster rates of growth by selected oysters. Selection resulted in oysters feeding at up to twice the rate and with greater metabolic efficiency than controls. A field experiment confirmed that selection leads to faster rates of feeding across a wide range of food concentrations. Selected oysters also grew more efficiently, at a smaller cost of growth (Cg): mean values for Cg were 0.43 J x J(-1) in selected individuals and 0.81 J x J(-1) in the controls. In contrast, oysters in both categories showed similar metabolic rates at maintenance, i.e., at a ration supporting zero growth. There was no evidence that differential energy allocation affected the balance between total metabolic requirements above and below zero net energy balance. By experimenting with selected and control oysters of different sizes and ages, then standardizing the data for size, we found no effects of age on the differences due to selection. Faster-growing oysters feed more rapidly; invest more energy per joule ingested; show a higher net growth efficiency; and are able to allocate less energy per unit of tissue growth, than slower-growing individuals.

A novel subtype of class II alcohol dehydrogenase in rodents. Unique Pro(47) and Ser(182) modulates hydride transfer in the mouse enzyme

Mice and rats were found to possess class II alcohol dehydrogenases with novel enzymatic and structural properties. A cDNA was isolated from mouse liver and the encoded alcohol dehydrogenase showed high identity (93.1%) with the rat class II alcohol dehydrogenase which stands in contrast to the pronounced overall variability of the class II line. The two heterologously expressed rodent class II enzymes exhibited over 100-fold lower catalytic efficiency (k(cat)/K(m)) for oxidation of alcohols as compared with other alcohol dehydrogenases and were not saturated with ethanol. Hydride transfer limited the rate of octanol oxidation as indicated by a deuterium isotope effect of 4.8. The mutation P47H improved hydride transfer and turnover rates were increased to the same level as for the human class II enzyme. Michaelis constants for alcohols and aldehydes were decreased while they were increased for the coenzyme. The rodent class II enzymes catalyzed reduction of p-benzoquinone with about the same maximal turnover as for the human form. This activity was not affected by the P47H mutation while a S182T mutation increased the K(m) value for benzoquinone 10-fold. omega-Hydroxy fatty acids were catalyzed extremely slow but functioned as potent inhibitors by binding to the enzyme-NAD(+) complex. All these data indicate that the mammalian class II alcohol dehydrogenase line is divided into two structurally and functionally distinct subgroups.

Activities of human alcohol dehydrogenases in the metabolic pathways of ethanol and serotonin

Alcohols and aldehydes in the metabolic pathways of ethanol and serotonin are substrates for alcohol dehydrogenases (ADH) of class I and II. In addition to the reversible alcohol oxidation/aldehyde reduction, these enzymes catalyse aldehyde oxidation. Class-I gammagamma ADH catalyses the dismutation of both acetaldehyde and 5-hydroxyindole-3-acetaldehyde (5-HIAL) into their corresponding alcohols and carboxylic acids. The turnover of acetaldehyde dismutation is high (kcat = 180 min-1) but saturation is reached first at high concentrations (Km = 30 mm) while dismutation of 5-HIAL is saturated at lower concentrations and is thereby more efficient (Km = 150 microm; kcat = 40 min-1). In a system where NAD+ is regenerated, the oxidation of 5-hydroxytryptophol to 5-hydroxyindole-3-acetic acid proceeds with concentration levels of the intermediary 5-HIAL expected for a two-step oxidation. Butanal and 5-HIAL oxidation is also observed for class-I ADH in the presence of NADH. The class-II enzyme is less efficient in aldehyde oxidation, and the ethanol-oxidation activity of this enzyme is competitively inhibited by acetate (Ki = 12 mm) and 5-hydroxyindole-3-acetic acid (Ki = 2 mm). Reduction of 5-HIAL is efficiently catalysed by class-I gammagamma ADH (kcat = 400 min-1; Km = 33 microm) in the presence of NADH. This indicates that the increased 5-hydroxytryptophol/5-hydroxyindole-3-acetic acid ratio observed after ethanol intake may be due to the increased NADH/NAD+ ratio on the class-I ADH.

Biosensing with G-protein coupled receptor systems

Many cell membrane bound receptors communicate with the inside of the cell through guanine nucleotide binding proteins (G-proteins). This holds also for olfactory receptor neurons, which respond to odorants with G-protein mediated increases in the concentration of cyclic adenosine 3', 5'-monophosphate (cAMP) and/or inositol 1,4,5-triphosphate (InsP3). These substances regulate the ionic conductivity of the wall of the cilia. We have studied a similar system, namely G-protein coupled alpha 2-adrenoceptors, present for example in the cells of certain fish scales. These receptors react on, catecholamines and the G-protein mediates a decrease in cAMP, which causes an aggregation of pigment containing granulas to the middle of the cells. The light transmission of the cell increases due to this aggregation. This simple physiological response has been used in a sensitive biosensor for noradrenaline and for pertussis toxin that is based on isolated fish scales from cuckoo wrasse (Labrus ossifagus). The results were obtained with a simple photometer. Measurements can be performed also on single isolated melanophores. The main purpose of this contribution is, however, to point out that G-protein coupled receptors together with a simple physiological response form a principle for biosensing, which could also be an interesting alternative for odour sensing.

Antihypertensive medication in clinical encounters

In managing hypertension, patient participation and understanding of the nature and significance of treatment are decisive. We analysed the communication between patient and physician with respect to antihypertensive medication at a follow-up appointment, and assessed patients' knowledge of their medication. The empirical data consist of audio-recordings from 51 hypertensive patients' follow-up appointment with their physicians. Thirty-three of these patients were interviewed in depth immediately after the appointment. The study was performed in primary health care centres and at a specialist clinic for hypertension. When discussing medications, patients mainly talked about experiences of being on medication, whereas physicians generally focused on the pharmacological effect and dosage of the drug. Physicians routinely asked about compliance with drug regimen, but seldom in any depth. Little effort was invested into discussing the effect and goal of therapy. The main finding was that patients had a very fragmentary understanding of the functional nature of their antihypertensive medication. This is unsatisfactory both from the point of view of treatment efficacy and also when considering the legal requirements of involving the patient in the decision making. The follow-up appointments studied gave few possibilities for the patient to learn about their antihypertensive medication.

Renal effects of alpha-ketoglutarate early after coronary operations

BACKGROUND

Alpha-ketoglutarate (alpha-KG) is a Krebs cycle intermediate and the carbon skeleton of glutamate. Alpha-ketoglutarate has provoked interest in heart surgery because of its proposed critical role in myocardial metabolism. This study investigates the role of alpha-KG in renal function after cardiac surgical procedures.

METHODS

Twenty-two patients with normal preoperative renal function were included in a prospective, randomized, and controlled study. Eleven patients received intravenous infusion of 30 g alpha-KG/hour after the operation. Measurements were performed before operation, immediately after operation, and after 30 minutes of alpha-KG infusion.

RESULTS

Renal blood flow was higher during alpha-KG infusion, 297% +/- 97% (of preoperative value), than in controls, 125% +/- 20% (p < 0.05). Filtration fraction was lower (12.3% +/- 0.05% versus 17.2% +/- 1.1%, p < 0.01), which prevented a significant difference in glomerular filtration rate. The renal arteriovenous differences of lactate, glutamate, glutamine, and glycine changed toward a net release during alpha-KG infusion.

CONCLUSIONS

Infusion of alpha-KG enhances renal blood flow early after coronary surgical procedures in patients with normal renal function. The mechanism is unclear, but could be associated with primarily metabolic effects, and may potentially convey a beneficial effect for renal function.

Echocardiography allows early detection and long-term survival after infarct free wall rupture

Approximately one third of free wall infarct ruptures are subacute and theoretically accessible for surgery. Two-dimensional echocardiography is an important tool in the early diagnosis of cardiac rupture. We report the successful treatment of a 74-year-old woman with subacute free wall rupture, who is still alive 3 years after surgery.

Structural and functional divergence of class II alcohol dehydrogenase--cloning and characterisation of rabbit liver isoforms of the enzyme

cDNAs coding for class II alcohol dehydrogenase were isolated from a rabbit-liver cDNA library. Deduced amino acid sequences show that isozymic forms of rabbit class II alcohol dehydrogenase exist, with a positional identity of 88.4%. A high variability in structure of class II alcohol dehydrogenase between the species is also reflected in function. The rabbit II-1 isozyme shows common characteristics with the human enzyme, but has a lower Km value for ethanol, 4.2 mM. The II-2 isozyme shows restriction for aliphatic alcohols longer than pentanol. For shorter alcohols the II-2 form has similar Km values as the II-1 isozyme, 5.5 mM for ethanol, but is a low activity variant with a 10-fold decrease in k(cat) values compared with II-1. Nevertheless, II-2 has a higher specificity for benzoquinone than II-1 due to a lower Km value, 80 microM compared with 1 mM, and is in this sense more like the human class II enzyme. In addition a rabbit class III alcohol dehydrogenase cDNA was isolated that encodes a typical class III enzyme/glutathione-dependent formaldehyde dehydrogenase. The finding of isozymic forms of class II alcohol dehydrogenase is in line with the evolution of the system of medium-chain alcohol dehydrogenases with different enzymes, different classes and different isozymes and further underline the complexity of the entire mammalian alcohol dehydrogenase system.

Hypertensive patients' knowledge of high blood pressure

OBJECTIVE

To investigate hypertensive patients' understanding of the circulatory system, in particular high blood pressure.

DESIGN

Semi-structured audio-taped interviews of patients immediately after a regular follow-up appointment with their physician.

SETTING

A primary health care centre and a specialist clinic (hypertension unit) in southern Sweden.

PATIENTS

33 hypertensive patients, consecutively selected.

MAIN OUTCOME MEASURE

Focus was set on the exploration of patients' understanding/knowledge.

RESULTS

In spite of a long history of hypertensive care, on average ten years, patients had a less than satisfactory understanding of their condition. Most patients knew their blood pressure values, but very few were able to give an account of what high blood pressure implies in functional terms. Knowledge of high blood pressure seems mainly to be derived from sources other than the health care system, in particular from the mass media. Knowledge of the risks associated with hypertension was quite good, as was the insight into how these risks could be managed.

CONCLUSION

An assessment of patient knowledge of high blood pressure ought to be a starting point for educational strategies that aim to deepen patients' understanding of their state of health.

Insulin and amino acid infusion after cardiac operations: effects on systemic and renal perfusion

OBJECTIVE

The purpose of this study was to answer two questions: (1) Does a mixed amino acid infusion enhance systemic and renal perfusion in the early postoperative period after heart operations? (2) Does the addition of insulin (glucose-insulin-potassium solution) provide additional effects to those of an amino acid infusion?

METHODS

Thirty-three male patients undergoing coronary artery bypass grafting (mean age 65.9 +/- 1.2 years) were included in a prospective, controlled, randomized study. Eleven patients (AA group) received infusion of mixed amino acids (11.4 gm), 11 patients (AA + GIK group) received infusion of mixed amino acids (11.4 gm) and insulin solution (225 IU insulin, glucose with glucose clamp technique, and potassium), and 11 patients served as control subjects.

RESULTS

Amino acid infusion alone had no effect on systemic vascular resistance or cardiac index but increased renal blood flow 51% +/- 11% (from 114 +/- 13 to 172 +/- 24 ml.min-1.m-2 in one kidney, p < 0.05 vs the control group). Insulin solution in addition to amino acid infusion reduced systemic vascular resistance 24% +/- 3% (from 1280 +/- 85 to 960 +/- 57 dyn.sec.cm-5, p < 0.05 vs the control and AA groups) and increased cardiac index 13% +/- 3% (from 2.3 +/- 0.2 to 2.6 +/- 0.2 L.min-1.m-2, p < 0.05 vs the control and AA groups). Insulin had no significant additive effect on renal blood flow.

CONCLUSIONS

Our data imply that (1) infusion of mixed amino acids enhances renal blood flow after cardiac operations but has no effect on systemic perfusion and (2) the addition of insulin solution improves systemic perfusion. The combined treatment may potentially reduce the risk of renal hypoperfusion injury in the postoperative period after coronary artery bypass grafting.

Alcohol dehydrogenase in human tissues: localisation of transcripts coding for five classes of the enzyme

Tissue distribution of the five identified classes of human alcohol dehydrogenase was studied by assessment of mRNA levels in 23 adult and four fetal tissues. Alcohol dehydrogenase of class I was found in most tissues, brain and placenta excluded, but expression levels among tissues differed widely. The distribution pattern of class III transcripts was consistent with those of housekeeping enzymes while, in contrast, class IV transcripts were found only in stomach. Transcripts of multiple length were detected for most classes and were due to different gene products arising through the use of different poly-A signals or transcription from different gene loci. Both class II and class V showed a pattern of liver-enriched expression. However, low mRNA levels were detected also in stomach, pancreas and small intestine for class II, and in fetal kidney and small intestine for class V. Significantly higher levels of class V transcripts were present in fetal liver when compared with levels in adult liver, which suggests that human class V is a predominantly fetal alcohol dehydrogenase.

Aldehyde dismutase activity of human liver alcohol dehydrogenase

Human alcohol dehydrogenases of class I and class II but not class III catalyse NAD+-dependent aldehyde oxidation in addition to the NADH-dependent aldehyde reduction. The two reactions are coupled, i.e. the enzymes display dismutase activity. Dismutase activity of recombinantly expressed human class I isozymes beta1beta1 and gamma2gamma2, class II and class III alcohol dehydrogenases was assayed with butanal as substrate by gas chromatographic-mass spectrometric quantitations of butanol and butyric acid. The class I gamma2gamma2 isozyme showed a pronounced dismutase activity with a high kcat, 1300 min(-1), and a moderate Km, 1.2 mM. The class I beta1beta1 isozyme and the class II alcohol dehydrogenase showed moderate catalytic efficiencies for dismutase activity with lower kcat values, 60-75 min(-1). 4-Methylpyrazole, a potent class I ADH inhibitor, inhibited the class I dismutation completely, but cyanamide, an inhibitor of mitochondrial aldehyde dehydrogenase, did not affect the dismutation. The dismutase reaction might be important for metabolism of aldehydes during inhibition or lack of mitochondrial aldehyde dehydrogenase activity.