Changes in carnitine levels in the embryonic chick heart during development

Carnitine levels in the embryonic chick heart were measured. The amount of total carnitine, free plus short chain acyl carnitine (acid-soluble fraction), and long chain acyl carnitine (acid-insoluble fraction) were examined at days 7, 11, 17, and 21 of incubation. These concentrations were found to correspond favorably with data from previous investigators with regard to variations in palmitoylcarnitine transferase enzyme activity, mitochondrial chain elongation activity, and palmitic acid oxidation.     

Plasma endothelin levels during myocardial ischemia and reperfusion

Endothelin, an endothelium-derived vasoconstrictive peptide, has a strong potency of coronary artery constriction. However, the role of endogeneous endothelin under pathophysiological conditions has not yet been known. In this study, we examined plasma endothelin concentration in dogs with myocardial ischemia and reperfusion. Anesthetized open-chest dogs underwent either 45 minutes occlusion of the left anterior descending coronary artery followed by 3 hours reperfusion, or 4-10 hours of continuous occlusion. Plasma concentration of endothelin from the central vein was measured by the highly sensitive enzyme-immunoassay. Plasma endothelin concentration increased 2.2-fold with the peak level at 60 minutes after release of the ligated artery, but occlusion per se caused no remarkable change. These data suggest that reperfusion of the occluded artery might be needed to increase the plasma concentration of endothelin in case of myocardial infarction.     

Met-enkephalin levels during PTCA-induced myocardial ischemia.

Met-enkephalin (Met-enk) has been demonstrated to modulate myocardial-ischemia mechanisms via the opioid receptors, but no studies are now available on Met-enk levels in the coronary circulation.In this experience Met-enk levels were evaluated in aortic root and in coronary sinus at baseline (T0), during PTCA induced transient ischemia (T1) and during reperfusion (T2). No significant differences were found at any time. Thus, it appears that there is no Met-enk extraction from the coronary circulation during provoked myocardial ischemia and no Met-enk release from the ischemic heart.     

心肌缺血／再灌注损伤后血清和心肌组织Leptin水平的变能

目的：观察大鼠心肌缺血／再灌注损伤对血清和心肌组织瘦素（Leptin）表达的影响,探讨Leptin在心肌缺血／再灌注损伤中的作用。方法：建立大鼠心肌缺血／再灌注模型,检测血清乳酸脱氢酶（LDH）和Leptin浓度,并用HE染色和免疫组织化学观察心肌组织病理学及Lepfin表达水平。结果：缺血组、再灌注组血清LDH水平显著升高（P〈0．05）,表明该模型制作成功,造成心肌局部一定程度的损伤。缺血组血清Leptin含量（6．34±2．49）ng／ml显著低于对照组（7．50±2．93ng／ml,P〈0．05）;再灌注后Leptin水平缓慢恢复,于再灌注2h时Leptin达到（8．32±1．74）ng／ml,恢复到损伤前水平（8．38±2．56）ng／ml,且随再灌注时间延长有升高趋势。免疫纽化显示与假手术纽心肌Leptin蛋白表达水平相比,其他四组均有显著降低（P〈0．01）,按缺血45min后再灌注1h组、缺血45min后再灌注3h组、单纯缺血45min组、缺血45min后再灌注2h组依次递减。结论：Leptin在心肌缺血／再灌注损伤后早期45min血中有明显减少,心肌组织中也明显表达下降。心肌组织病理损伤与Leptin的改变可能有一定的关系。     

Antioxidant vitamin levels and glutathione peroxidase activity during ischemia/reperfusion in myocardial infarction

The consequences of increased oxidative stress, measured as the level of malondialdehyde (MDA) during ischemia/reperfusion, were studied in 48 patients in the acute phase of myocardial infarction (AMI) and a control group (21 blood donors). The serum levels of alpha-tocopherol and beta-carotene were followed. Immediately after the treatment onset the level of alpha-tocopherol started to decrease, reaching a plateau after 24 h. The consumption of beta-carotene was delayed by 90 min. Steady decline was detected during the whole time interval studied (48 h). Glutathione peroxidase (GPx) activity, as a representative of antioxidant enzymes, was estimated in whole blood. The influx of oxygenated blood was accompanied by a stimulation of GPx activity, which reached its maximum at the time of completed reperfusion. When comparing the AMI patients with the control group, the levels of MDA were found significantly increased, which indicates that oxidative stress is already increased during ischemia. Lower antioxidant levels found in the patients might either already be the result of vitamin consumption during ischemia or be a manifestation of their susceptibility to AMI. Monitored consumption of alpha-tocopherol and beta-carotene during reperfusion indicated that in the case of patients, whose level of antioxidant vitamins is below the threshold limit, a further substantial decrease of antioxidant vitamins during reperfusion could enhance the oxidative damage of the myocardium.     

Changes in concentration of amino acids and other metabolites during hypothermic perfusion of the canine kidney

Changes in the concentration of amino acids and other metabolites were determined in the perfusate during 24 hr of ex vivo hypothermic perfusion of dog kidneys. There was an increase in concentration of most of the amino acids. Two patterns were identified. One showed an increase in concentrations up to 12 hr, and then a leveling off as exemplified by alanine, serine, and glutamate. The other pattern was one of persistent elevation as exemplified by phenylalanine, threonine, and methionine. Glucose, lactate, pyruvate, sodium, potassium, pH, and pO2 were also measured in the perfusate. The results suggest that a degradation of kidney protein may occur during the first 24 hr of perfusion. The levels of other metabolites measured support the fact that glycolysis is responsible for a considerable portion of the total energy production in the kidney under hypothermia.     

Arrhythmogenic properties of phospholipid metabolites associated with myocardial ischemia

Several observations suggest that the accumulation of metabolites within ischemic regions may contribute to the electrophysiological derangements characteristic of ischemic myocardium. We, and more recently others, have detected an increase in lysophosphoglycerides (LPGs) in ischemic tissue in vivo as well as in effluents from ischemic regions. At comparable concentrations, LPGs induce electrophysiological alterations in vitro analogous to changes seen in vivo with ischemia. Experiments with [14C]lysophosphatidylcholine indicated that incorporation comprising less than 1% of total cellular phospholipid is sufficient to induce electrophysiological derangements in isolated ventricular muscle. Reduction of pH to 6.7, analogous to the fall seen within minutes in ischemic tissue in vivo, potentiates the electrophysiological actions markedly without increasing membrane incorporation. In recent studies the activity of enzymes potentially responsible for the accumulation of LPGs during ischemia has been found to be altered by concomitants of ischemia, including increased concentrations of H+ and long-chain acyl carnitine. Thus, accumulation of LPGs and related compounds may contribute substantially to induction of electrophysiological derangements accompanying ischemia and may be amenable to therapeutic manipulation designed to alleviate malignant ventricular dysrhythmia.     

Changes in the levels of glycolysis and tricarboxylic acid cycle metabolites in cat tissues during periodontosis

The predominance of restored substrates in the bone system and liver of cats under chronic parodontosis evidence for intensification of reproduction properties of NAD-pairs and causes inhibition of glycolysis and activation of gluconeogenesis. A high content of alpha-ketoglutarate and isocitrate in tissues in a result of lipogenesis inhibition. Under the lower rate of glycolysis, activation of proteolysis and transamination reactions amino acids are the major contributors to pyruvate. Under the acute course of the disease with the development of the inflammatory process the quantity of pyruvate grows sharply in the parodont tissue, as well as oxidative properties of NAD-pairs intensify and lipogenesis accelerates. This is confirmed by a decrease in the alpha-ketoglutarate and isocitrate content in the tissues.     

Dinitrosyl iron complexes with glutathione in rat myocardial tissue during regional ischemia and postischemic reperfusion

Injection of dinitrosyl iron complexes with glutathione at the onset of 40-min regional myocardial ischemia in rat was shown to exert a clear cardioprotective action by decreasing the infarct size and suppressing the cardiac rhythm disturbance. After introducing the preparation, its effective accumulation with protein thiol-containing ligands in the myocardial tissue was registered be the EPR method. It was also found that in postischemic reperfusion, the rate of decrease in the content of these complexes in the ischemic area increases, which reflects effective scavenging of short-lived reactive oxygen species by the dinitrosyl iron complexes.     

Effect of various levels of supplementation with sodium pivalate on tissue carnitine concentrations and urinary excretion of carnitine in the rat

In previous studies, sodium pivalate has been administered to rats in their drinking water (20 mmoles/L; equivalent to 0.3% of the diet) as a way to lower the concentration of carnitine in tissues and to produce a model of secondary carnitine deficiency. Although this level of supplementation results in a marked decrease in carnitine concentration in a variety of tissues, it does not produce the classical signs of carnitine deficiency (i.e., decreased fatty acid oxidation and ketogenesis). The present study was designed (1) to determine if increasing the level of pivalate supplementation (0.6, 1.0% of the diet) would further reduce the concentrations of total and free carnitine in rat tissues without altering growth or food intake, and (2) to examine the effect of length of feeding (4 vs. 8 weeks) on these variables. Male, Sprague-Dawley rats were randomly assigned to either a control (0.2% sodium bicarbonate) or experimental diet (0.3, 0.6, 1.0% sodium pivalate) for either four or eight weeks. Animals (n = 6/group) were housed in metabolic cages; food and water were provided ad libitum throughout the study. Supplementation with sodium pivalate did not alter water intake or urine output. Ingestion of a diet containing 1.0% pivalic acid decreased food intake (g/day; P < 0.05), final body weight (P < 0.007), and growth rate (P < 0.001) after four weeks. The concentration of total carnitine in plasma, heart, liver, muscle, and kidney was reduced in all experimental groups (P < 0.001), regardless of level of supplementation or length of feeding. The concentration of free carnitine in heart, muscle, and kidney was also reduced (P < 0.001) in rats treated with pivalate for either four or eight weeks. The concentration of free carnitine in liver was reduced in animals supplemented with pivalate for eight weeks (P < 0.05), but no effect was observed in livers from rats treated for four weeks. Excretion of total carnitine and short chain acylcarnitine in urine was increased in pivalate supplemented rats throughout the entire feeding period (P < 0.001). Free carnitine excretion was increased during Weeks 1 and 2 (P < 0.01), but began to decline during Week 3 in experimental groups. During Weeks 6 and 8, free carnitine excretion in pivalate supplemented rats was less than that of control animals (P < 0.01). In summary, no further reduction in tissue carnitine concentration was observed when rats were supplemented with sodium pivalate at levels greater than 0.3% of the diet. Food intake (g/day) and growth were decreased in rats fed a diet containing 1.0% sodium pivalate. These data indicate that maximal lowering of tissue carnitine concentrations is achieved by feeding diets containing 0.3% sodium pivalate or less.     

Dinitrosyl complexes of iron with glutathione in the rat myocardial tissue during regional ischemia and postischemic reperfusion

The injection of dinitrosyliron iron complexes with glutathione at the onset of 40-min rat regional myocardial ischemia was shown to exert a clear cardioprotective action by decreasing the infarct size and suppressing the cardiac rhythm disturbance. After the introduction of the preparation, its effective accumulation with protein thiol-containing ligands in the myocardial tissue was registered be the EPR method. It was also found that, as a result of postischemic reperfusion, the rate of the decrease in the content of these complexes in the ischemic area increases, which demonstrates the effective scavenging of short-lived reactive oxygen species by molecules of dinitrosyl iron complexes.     

Actin is oxidized during myocardial ischemia

Exposure of isolated rat hearts to 30 min global ischemia followed by 60 min reperfusion resulted in a significant 80% increase (p <.05) in actin content of carbonyl groups, which was associated with significant depression (p <.05) of postischemic contractile function. This result supports the hypothesis that one mechanism of postischemic contractile dysfunction may be oxidation of contractile proteins.     

Acetyl-L-carnitine supplementation restores decreased tissue carnitine levels and impaired lipid metabolism in aged rats

The effects of long-term carnitine supplementation on age-related changes in tissue carnitine levels and in lipid metabolism were investigated. The total carnitine levels in heart, skeletal muscle, cerebral cortex, and hippocampus were approximately 20% less in aged rats (22 months old) than in young rats (6 months old). On the contrary, plasma carnitine levels were not affected by aging. Supplementation of acetyl-l-carnitine (ALCAR; 100 mg/kg body weight/day for 3 months) significantly increased tissue carnitine levels in aged rats but had little effect on tissue carnitine levels in young rats. Plasma lipoprotein analyses revealed that triacylglycerol levels in VLDL and cholesterol levels in LDL and in HDL were all significantly higher in aged rats than in young rats. ALCAR treatment decreased all lipoprotein fractions and consequently the levels of triacylglycerol and cholesterol. The reduction in plasma cholesterol contents in ALCAR-treated aged rats was attributable mainly to a decrease of cholesteryl esters rather than to a decrease of free cholesterol. Another remarkable effect of ALCAR was that it decreased the cholesterol content and cholesterol-phospholipid ratio in the brain tissues of aged rats. These results indicate that chronic ALCAR supplementation reverses the age-associated changes in lipid metabolism.     

AMPK mediates autophagy during myocardial ischemia in vivo

We have recently shown that autophagy is induced by ischemia and reperfusion in the mouse heart in vivo. Ischemia stimulates autophagy through an AMP activated protein kinase (AMPK)-dependent mechanism, whereas reperfusion after ischemia stimulates autophagy through a Beclin 1-dependent, but AMPK-independent, mechanism. Autophagy plays distinct roles during ischemia and reperfusion: autophagy may be protective during ischemia, whereas it may be detrimental during reperfusion. We will discuss the role of AMPK in mediating autophagy during myocardial ischemia in vivo.     

Early activation of IKKbeta during in vivo myocardial ischemia

We have demonstrated that in vitro brief ischemia activates nuclear factor (NF)-kappaB in rat myocardium. We report in vivo ischemia-reperfusion (I/R)-induced NF-kappaB activation, IkappaB kinase -beta (IKKbeta) activity, and IkappaBalpha phosphorylation and degradation in rat myocardium. Rat hearts were subjected to occlusion of the coronary artery for up to 45 min or occlusion for 15 min followed by reperfusion for up to 3 h. Cytoplasmic and nuclear proteins were isolated from ischemic and nonischemic areas of each heart. NF-kappaB activation was increased in the ischemic area (680%) after 10 min of ischemia and in the nonischemic area (350%) after 15 min of ischemia and remained elevated during prolonged ischemia and reperfusion. IKKbeta activity was markedly increased in ischemic (1,800%) and nonischemic (860%) areas, and phosphorylated IkappaBalpha levels were significantly elevated in ischemic (180%) and nonischemic (280%) areas at 5 min of ischemia and further increased after reperfusion. IkappaBalpha levels were decreased in the ischemic (45%) and nonischemic (36%) areas after 10 min of ischemia and remained low in the ischemic area during prolonged ischemia and reperfusion. The results suggest that in vivo I/R rapidly induces IKKbeta activity and increases IkappaBalpha phosphorylation and degradation, resulting in NF-kappaB activation in the myocardium.