Reversibility of chronic alcohol cardiac depression: 31P magnetic resonance spectroscopy in hamsters

[Pharmacological fMRI : new possibilities for assessing the efficacy of analgesic agents]

Pain is a complex subjective phenomenon that so far cannot be objectively quantified by any standardized procedure. This fact renders it also difficult to measure the efficacy of analgesic drugs. In recent years the application of functional magnetic resonance imaging (fMRI) has significantly increased our current knowledge about the brain physiological correlates of pain in humans. The technique is non-invasive and detects the increased blood flow into neuronally active brain regions based on the so-called BOLD (blood oxygenation level dependent) effect of T2-weighted MRI. This paper gives an overview of the application of pharmacological fMRI (phfMRI) as an approach to evaluate the efficacy of analgesics. In contrast to EEG- and MEG-based methods phfMRI allows more flexibility in the design of experimental paradigms and stimulus protocols to account for the diversity of clinical pain types (inflammatory pain, tactile allodynia etc.) or their dependence upon psychological circumstances (anxiety, depression, stress) in which pain occurs. However, in order to specifically refer results from phfMRI to the neuronal processes underlying pain, future research needs to increase the understanding of the mechanisms underlying the neurovascular coupling reaction represented by the BOLD technique. The same applies for the influence of cerebrovascular diseases on the BOLD response.

The acute and chronic effects of alcohol upon cardiac nucleotide status

The aim of the investigation was to ascertain the biochemical and morphological basis for the functional impairments in the heart due to alcohol. In chronic studies rats were fed a nutritionally complete liquid diet containing 35% of total calories as ethanol, controls were pair-fed identical amounts of the same diet in which ethanol was replaced by isocaloric glucose. In acute studies rats were injected with ethanol at a dose of 75 mmol/kg body weight. Pre-treatment of acute ethanol-dosed rats with cyanamide (ALDH inhibitor) was designed to raise acetaldehyde levels. In chronic studies ventricular adenine nucleotides, ATP, ADP and AMP; NAD(+), ATP ratios and the energy charge showed no alteration after 6 weeks of alcohol feeding. Light and electron microscopy sections indicated very little structural damage to muscle fibres and organelles (especially the mitochondria) in both atria and ventricles. Ventricular fibre diameters, throughout the different ranges, showed no significant differences between chronically alcohol and control-fed rats. In acute studies an increase in ventricular AMP levels (micromoles/g wet weight) occurred following cyanamide and cyanamide + ethanol treatment (+57%, p < 0.025 and +76%, p<0.01, respectively), but not as a consequence of ethanol alone. Cyanamide+ethanol caused marked elevation in ADP levels (+28%, p < 0.05) and again ethanol was without effect. ATP and GTP levels were not altered by any of the acute treatments. The energy charge was slightly reduced in both cyanamide and cyanamide+ethanol groups (-8%, p < 0.01 and -7%, p < 0.05, respectively), but not by ethanol alone. In conclusion, chronic alcohol appears to have minimal effects upon cardiac nucleotides which suggest that possible adaptive mechanisms are induced during the 6-week period and that alternative pathways other than defects in adenine nucleotide concentrations are involved in the pathogenesis of AHMD. The acute study suggests that the heart is resilient to toxic levels of alcohol and acetaldehyde in terms of ATP and GTP levels, despite the elevated AMP, ADP and GDP levels.

Chronic alcohol-induced changes in cardiac contractility are not due to changes in the cytosolic Ca2+ transient

Long-standing heavy alcohol consumption acts as a chronic stress on the heart. It is thought that alcohol-induced changes of contractility are due to altered Ca2+ handling, but no measurements of cytosolic Ca2+ ([Ca2+]c) after chronic alcohol exposure have been made. Therefore experiments were performed to determine whether alcohol-induced changes in contractility are due to altered Ca2+ handling by measuring [Ca2+]c (indo 1) in hearts from rats drinking 36% ethanol for 7 mo and age-matched controls. Peak left ventricular pressure was depressed (-16%), whereas rates of contraction (12%) and relaxation (14-20%) were faster in alcohol-exposed hearts. Systolic [Ca2+]c (808 +/- 45 vs. 813 +/- 45 nM), diastolic [Ca2+]c (195 +/- 11 vs. 193 +/- 10 nM), and rates of [Ca2+]c rise and decline were the same in alcohol-exposed and control hearts. Protein levels of Ca2+-handling proteins, sarcoplasmic reticulum Ca2+-ATPase and phospholamban, were the same in myocytes isolated from alcohol-exposed and control hearts (SDS-polyacrylamide gel). These data suggest that chronic alcohol-induced contractile changes are not due to altered Ca2+ handling but may be due to changes at the level of the myofilament. As a first step in elucidating the mechanism(s) of alcohol-induced changes at the myofilament, we assessed myosin heavy chain (MHC) isoform content (SDS-polyacrylamide gel). alpha-MHC was decreased relative to beta-MHC (a/a + b = 0.55 +/- 0.03 vs. 0.66 +/- 0.02; P < 0.02) in alcohol-exposed hearts, which cannot account for the observed alcohol-induced contractile changes. In conclusion, changes of myocardial contractility due to chronic alcohol exposure do not result from altered Ca2+ handling but from changes at the level of the myofilament that do not involve MHC isoform shifts.

Ethanol feeding produces deficiencies in left ventricle total RNA, total DNA and mitochondrial ribosomal RNA

Chronic alcoholism causes a variety of ultrastructural, biochemical and functional alterations in the myocardium, but the underlying mechanisms are not well understood. Molecular changes that developed in the left ventricles of rats fed for 1 to 24 weeks on liquid diets containing ethanol as 36% of total calories were analyzed. Total tissue RNA and DNA were chemically extracted and measured by spectroscopic methods; mitochondrial DNA and mitochondrially-coded ribosomal RNA were measured at the 12s rRNA region by a quantitative polymerase chain reaction method; mitochondrial protein and enzyme activities were assayed. Ethanol-fed rats had 83.9 +/- 2.9% (mean +/- S.E.M.) as much DNA/g tissue and 74.7 +/- 3.9% as much total left ventricle DNA as pair-fed controls (P < 0.001). The alcoholics had 71.4 +/- 1.7% as much RNA/g tissue and 64.4 +/- 2.7% as much total left ventricle RNA as controls (P < 0.001). Mitochondrially-coded 12s rRNA was a lower proportion of total left ventricle RNA in all of the alcoholics; it was only 59.9 +/- 4.6% of control values (P < 0.001). Total left ventricle 12s rRNA was < 40% of normal. There was little or no change in mitochondrial DNA levels measured at the 12s location. Mitochondrial cytochrome contents were reduced 26-38% in the ethanol-fed rats, but only after 24 weeks. This study shows that experimental alcoholism produces rapid and sustained decreases in left ventricle total RNA and DNA and mitochondrial ribosomal RNA. The observed effects would be expected to have a major impact on left ventricle structural integrity and functional capacity.

Recovery of muscular energy status in chronic alcoholics after 2 weeks of abstinence

Repeated and excessive consumption of alcohol leads to pathophysiological disorders in skeletal muscles. A successful management of this syndrome requires a strict abstinence and a nutritionally adequate diet. We propose here a simple and noninvasive investigation using 31P magnetic resonance spectroscopy (MRS) to monitor the recovery of the basal energy status of eminence thenar muscles from documented chronic alcoholic patients during a controlled 15-day period of abstinence. Cessation of alcohol abuse induced a significant recovery of the PCr/(PCr+P(i)) ratio otherwise depressed before the abstinence. On the contrary, the relative level of free inorganic phosphate decreased, whereas intracellular pH was not affected. These results demonstrate (a) the rapid improvement of basal muscular energy metabolism during abstinence for patients with a chronic and heavy alcohol consumption, and (b) the feasibility of a follow-up of this recovery by serial examinations using 31P MRS.

Alcoholic cardiomyopathy

Chronic alcoholism is one of the most important causes of dilated cardiomyopathy, and a large proportion of chronic alcoholics demonstrate impairment of cardiac function. The development of cardiac dysfunction is apparently related to the total lifetime dose of ethanol. Studies in experimental animals have demonstrated that both acute and chronic ethanol administration impair cardiac contractility. However, the relationship, if any, between the acute effects of alcohol and the development of irreversible cardiomyopathy remain to be elucidated.

Effects of ethanol on the contractile function of the heart: a review

Chronic ethanol consumption leads to a number of alterations in the contractile function of the heart and is a leading cause of cardiomyopathy. Ethanol also has an acute negative inotropic effect mediated by direct interaction with cardiac muscle cells, although this action is often masked by indirect actions resulting from enhanced release of catecholamines in vivo. This article reviews the effects of ethanol on the contractile function of the heart. The specific targets affected by ethanol in cardiac muscle cells are discussed in terms of potential mechanisms underlying the depressions of contractility resulting from both acute and chronic actions of ethanol.

Activation of glycolysis with isoproterenol but not digoxin reverses chronic alcohol depression in hamster hearts

The purpose of this study was to confirm that an agent, which increases diastolic [Ca2+]i, namely digoxin, depresses cardiac performance, mitochondrial activity, and glycolysis in chronic alcohol-treated and myopathic hearts, and that an agent, which lowers diastolic [Ca2+]i, namely isoproterenol, activates cardiac performance, mitochondrial activity, and glycolysis in these animals. Energy levels, glycolysis, mitochondrial activity, hemodynamics, and cAMP were studied in isolated hearts from three groups of animals, i.e., 9-month control hamsters, hamsters given 50% alcohol until 9 months of age, and 6-month-old cardiomyopathic hamsters in heart failure. Isolated hearts were perfused with either a control medium, a medium containing isoproterenol, digoxin, or digoxin + isoproterenol. Measurement of phosphomonoester sugars, and glucose-6-phosphate, were used to assess glycolytic activity. Oxygen consumption was used to analyze mitochondrial activity. All hearts perfused with either isoproterenol or isoproterenol + digoxin showed an increase in developed pressure, rate-pressure-product, and a decrease in end-diastolic pressure. Isoproterenol activated mitochondrial activity and glycolysis in hearts from myopathic and chronic alcohol hamsters. Based on 31P-NMR studies, isoproterenol or isoproterenol + digoxin improved the over-all energy state of hearts from cardiomyopathic hamsters, but not hearts from control and chronic alcohol hamsters. Digoxin alone augmented the rate-pressure-product and oxygen consumption in control hearts but not hearts from myopathic and chronic alcohol hamsters. Digoxin caused an increase in end-diastolic pressure in myopathic and chronic alcohol hearts but not control hearts. Digoxin depressed glycolysis and worsened the energy state in hearts from cardiomyopathic and chronic alcohol hamsters, but not hearts from control hamsters. In conclusion digoxin, but not isoproterenol nor isoproterenol + digoxin, depressed cardiac performance and glycolysis as well as high energy phosphates in cardiomyopathic and chronic alcohol hearts. Isoproterenol added to digoxin negated the adverse effects of digoxin in cardiomyopathic and chronic alcohol hearts.

Cardiac function and metabolism after chronic alcohol consumption: adaptation, reversibility, and effects of verapamil

Hamsters were fed 50% alcohol instead of drinking water for up to 42 weeks (average serum alcohol levels were 0.12 +/- 0.06 gm/dl during the 42 weeks). One group of hamsters (28 weeks) was given verapamil 3 days before they were killed. Two groups were withdrawn from alcohol acutely (3 days before they were killed) at 14 and 28 weeks. High-energy phosphate compounds were studied in isolated hearts with 31P-MRS standardized by freeze clamping the tissue. Hemodynamics of the heart were monitored throughout the study. After 7 and 14 weeks of alcohol ingestion, developed pressure and the phosphorylation potential were depressed in the hearts of chronically treated hamsters. At 28 and 42 weeks developed pressure increased but was significantly below baseline values; however, the phosphorylation potential and [pH]i returned to baseline values at 28 and 42 weeks. Throughout the 7 to 42 weeks of alcohol ingestion the alcohol-treated hamsters had a significantly higher end-diastolic pressure as compared with control animals. Withdrawal of alcohol (3 days before the hamsters were killed) reversed the depression of developed pressure and the phosphorylation potential. Acute administration of verapamil (therapeutic dose 3 days before they were killed) to hamsters given alcohol for 28 weeks reversed the depressed hemodynamic values. Overall the data suggest an adaptation of the heart to continuing alcohol consumption, which was related to normalization of the phosphorylation potential and [pH]i and partial alleviation of functional depression.

Glycolysis in heart failure: a 31P-NMR and surface fluorometry study

Glycolysis is slow in the heart, especially in the cardiomyopathic heart. Glycolysis is partially rate-limited by phosphofructokinase (PFK), an enzyme which is inhibited by calcium (Ca2+)i and hydrogen ions (H+)i and activated by cAMP. (H+)i and (Ca2+)i are augmented in cardiomyopathy. With glucose as the only substrate (NADH)/(NAD) the phosphorylation potential and developed pressure were significantly lower, and concentrations of phosphomonoester sugars and hydrogen ions (H+)i were significantly higher in isolated cardiomyopathic hearts as compared to healthy hamster hearts. Pyruvate lowered diastolic (Ca2+)i in cardiomyopathic hamster hearts. With pyruvate as the substrate (NADH)/(NAD), the phosphorylation potential and developed pressure increased significantly and concentrations of phosphomonoester sugars (PME), (H+)i and diastolic (Ca2+)i decreased significantly in myopathic hamster hearts. The results suggest that late heart failure in the myopathic hamster is associated with calcium and/or hydrogen ion-induced inhibition of glycolysis.

Ethanol protects the heart against the calcium paradox injury

Rat hearts were depleted of Ca2+ (less than 10(-9) M) for 10 min, followed by 15 min of Ca2+-repletion. The calcium paradox injury occurs during Ca2+-repletion, after a period of calcium depletion. The calcium paradox injury was assessed by percent recovery (hemodynamics, [Ca2+]i, and energy levels) during Ca2+-repletion. A decrease in Na+ concentration during Ca2(+)-depletion did not allow for recovery during Ca2(+)-repletion, however 2.5% and 5% ethanol during Ca2(+)-depletion allowed for an approximate 50% recovery during Ca2(+)-repletion. A combination of ethanol (2.5% or 5%) with a low extracellular Na+ concentration (88 mM) allowed for complete recovery. Ethanol prevented a depletion of diastolic [Ca2+]i during Ca2(+)-depletion, and allowed for a return of normal diastolic [Ca2+]i during Ca2(+)-repletion. Ethanol modulates the activity of the Na+/Ca2+ exchanger and protects against the Ca2(+)-paradox injury.