Cardioprotective effects of various class I antiarrhythmic drugs in canine hearts.

This study was designed to clarify the cardioprotective effects of various class I antiarrhythmic drugs, i.e., aprindine, disopyramide, flecainide, lidocaine, mexiletine, pentisomide and propafenone, on the ischemic heart. Sixty-one adult mongrel dogs were classified into eight groups according to premedication: 1) control group, physiologic saline solution was administered intravenously 25 min before left anterior descending coronary artery ligation; 2) aprindine group, 3 mg/kg body weight of aprindine intravenously; 3) disopyramide group, 2 mg/kg of disopyramide intravenously; 4) flecainide group, 2 mg/kg of flecainide intravenously followed by drip infusion of 100 micrograms/kg per min; 5) lidocaine group, 2 mg/kg of lidocaine intravenously followed by drip infusion of 100 micrograms/kg per min; 6) mexiletine group, 3 mg/kg per min of mexiletine intravenously followed by drip infusion of 15 micrograms/kg per min; 7) pentisomide group, 5 mg/kg intravenously; and 8) propafenone group, 2 mg/kg intravenously. Arterial blood pressure and electrocardiogram were monitored throughout the experiment. Two hours after coronary occlusion, the heart was excised. Myocardial mitochondria were prepared and mitochondrial function (the respiratory control index and the rate of oxygen consumption in state III) was measured polarographically. Fractionation of myocardial tissues was performed and the lysosomal enzyme (N-acetyl-beta-glucosaminidase and beta-glucuronidase) activities among fractions were measured. No significant hemodynamic changes were observed compared with the control group except for those in the disopyramide and flecainide groups; that is, decrease in heart rate without changes in blood pressure compared with the control group was observed. All antiarrhythmic drugs effectively prevented the development of ventricular arrhythmias associated with ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of antiarrhythmic agents classified as class III group on ischaemia-induced myocardial damage in canine hearts.

1. The cardioprotective effects of antiarrhythmic agents classified as class III, amiodarone, sotalol and E-4031, were investigated in anaesthetized dogs. 2. The left anterior descending coronary artery was occluded for 2 h. 3. Heart mitochondria were prepared from both the ischaemic and non-ischaemic areas, and their function was estimated polarographically. 4. Activities of the lysosomal enzymes, N-acetyl-beta-glucosaminidase and beta-glucuronidase, were measured in each fraction. 5. Two hour occlusion induced ventricular arrhythmias, and amiodarone, sotalol and E-4031 greatly suppressed the development of arrhythmias. 6. Amiodarone, sotalol and E-4031 significantly protected mitochondria against ischaemia, and prevented ischaemia-induced leakage of lysosomal enzymes. 7. Antiarrhythmic agents classified as class III show cardioprotective effects, which might participate in their antiarrhythmic effect.

New therapeutic approach to aortic dissection complicated by cardiac tamponade.

The management of aortic dissection with cardiac tamponade may result in increased blood pressure and thereby itself make the aortic dissection worse. Nevertheless, it is important to prevent cardiac failure caused by cardiac tamponade. We describe a case of aortic dissection with cardiac tamponade. Echocardiography and aortography showed DeBakey IIIb-type aortic dissection with retrograde dissection, complicated by cardiac tamponade and aortic insufficiency. To treat this condition, a new therapeutic approach was undertaken. A vasodilator was administered, then pericardiocentesis guided by echocardiography was performed. To prevent abrupt elevation of blood pressure in response to the relief of cardiac tamponade, the pericardial aspiration was carried out slowly--it took four hours for the complete drainage of 415 ml of blood--and a vasodilator, sodium nitroprusside, was administered. After drainage, cardiac function was reversed fully, and the systolic pressure was controlled under 140 mmHg. Then, using extra-corporeal circulation, the surgical procedure was performed successfully. We conclude that it is useful to treat cardiac tamponade by controlling blood pressure with slow drainage and use of a vasodilator in preparation for performing the surgical procedure.

The role of leukotoxin (9,10-epoxy-12-octadecenoate) in the genesis of coagulation abnormalities.

This study was designed to clarify whether or not leukotoxin (9, 10-epoxy-12-octadecenoate), which is biosynthesized by neutrophils, might be involved in the genesis of coagulating abnormalities. Twelve dogs were divided into 2 groups. In the test group (n = 6), 100 mumol/kg of leukotoxin was injected intravenously, and in the control group (n = 6), 100 mumol/kg of linoleate was injected. In each group, a series of blood samples were collected and used for coagulation studies. After the end of the experimental period, a histological study was performed on organs removed from the dogs. In the leukotoxin group, fibrin and fibrinogen degradation products (FDP) was increased time-dependently. Fibrinogen was decreased, and prothrombin time and activated partial thromboplastin time were prolonged in parallel with the increase in FDP. A decrease in number of platelets was also observed. Intravascular coagulation was observed in sections of lung. These data were compatible with a diagnosis of disseminated intravascular coagulation (DIC). No significant changes in these parameters were observed in the linoleate group. Leukotoxin has been confirmed to show antifungal and antibacterial activity, and its production might be a defensive response to infection. Over-production of leukotoxin associated with severe infection might therefore account for infection-induced DIC.

[Leukotoxin and pulmonary injury].

In spite of the development of various antibiotics, management of elderly patients with pneumonia remains an important problem. It is suggested that adult respiratory distress syndrome (ARDS) and disseminated intravascular coagulation (DIC) often occur in elderly patients with pneumonia. Although neutrophils are suggested to be involved in the genesis of these conditions, details remain unknown. We demonstrated that a highly cytotoxic substance, 9,10-epoxy-12-octadecenoate, is biosynthesized from linoleate by human neutrophils, thus it was named leukotoxin. Leukotoxin was detected in lung lavages from patients with ARDS. In these lung lavages, increases in albumin concentration and angiotensin converting enzyme (ACE) activity were also observed. Similar results were observed in lung lavages from rats after exposure to hyperoxia for 60 hours in an experimental model of ARDS. Intravenous administration of leukotoxin (100 mumol/kg) caused lung edema. Albumin concentration and ACE activity were increased in lung lavages of rats receiving leukotoxin. In contrast, these changes were not observed in rats administered with linoleate. Furthermore, administration of leukotoxin (100 mumol/kg) caused coagulation abnormality, i.e., increase in fibrin-fibrinogen degradation products, decrease in fibrinogen, and prolongation of activated partial thromboplastin time and prothrombin time. Administration of linoleate did not induce these changes. It is indicated that O2- was produced by respiratory burst enzyme located in neutrophil plasma membrane, and that hydroxyl radicals derived from O2- by Fenton reaction were responsible for leukotoxin synthesis. From our results, leukotoxin, a product of hydroxyl radicals and linoleate, might be responsible for the genesis of ARDS and DIC.

[The effect of flecainide on 2 hour occlusion-induced myocardial damages in dog].

This study was designed to clarify whether or not flecainide have cardioprotective effect on ischemic myocardium. Nineteen dogs anesthetized and subjected to 2 h coronary occlusion, were divided into 2 groups. In the control group, physiological saline was infused, and in the flecainide group, 2 mg/kg of flecainide acetate and followed by 100 micrograms/kg/min continuous infusion. To assess the cardioprotective effect, mitochondrial function and lysosomal enzyme activities were measured. Two hours after occlusion, mitochondria were prepared from both ischemic and non-ischemic areas in each group, and their function (respiratory control index, and the rate of oxygen consumption in state III respiration) were measured polarographically with succinate as substrate. Fractionation of myocardial tissue from both non-ischemic and ischemic areas was performed according to the method of Weglicki et al, and the activities of lysosomal enzymes (N-acetyl-beta-glucosaminidase, and beta-glucuronidase) were measured. In the control group, mitochondrial dysfunction and leakage of lysosomal enzymes induced by 2 h occlusion were observed. On the contrary, administration of flecainide maintained significantly mitochondrial function, and prevented significantly leakage of lysosomal enzymes. These results indicated that flecainide had cardioprotective effect as well as antiarrhythmic effects in ischemic myocardium.

Effect of 3-(2,2,2-trimethylhydrazinium) propionate, gamma-butyrobetaine hydroxylase inhibitor, on isoproterenol-induced mitochondrial dysfunction.

The present study was designed to investigate whether or not reduction of carnitine content could protect isoproterenol (ISP)-induced myocardial injury using 3-(2,2,2-trimethylhydrazinium) propionate (TMHP), gamma-butyrobetaine hydroxylase inhibitor. Rats were divided into 4 groups; the control group: untreated, the TMHP-1 group: TMHP (100 mg/kg) was administered intraperitoneally, and ISP (10 mg/kg) was administered subcutaneously on the following day, the TMHP-7 group: TMHP (100 mg/kg) for 7 successive days, and ISP (10 mg/kg) on the eighth day, the ISP group: ISP (10 mg/kg) was administered. Rats were cervically dislocated 15 hours after ISP administration, and heart mitochondrial electron-transport activity (NADH-cytochrome c reductase, succinate-cytochrome c reductase, and cytochrome c oxidase) were measured enzymatically. Activity of succinate-cytochrome c reductase was not affected significantly by ISP, however, NADH-cytochrome c reductase and cytochrome c oxidase were significantly reduced in the ISP and TMHP groups. Administration with TMHP for 7 successive days lessened the reduction of the activities. Mitochondrial electron-transport system plays an important role in cellular energy transduction. These results suggested that mitochondrial dysfunction induced by ISP is related to carnitine-dependent fatty acid metabolism and that TMHP reduces the myocardial injury.

Effect of the alpha 1-blocker bunazosin on reperfusion-induced mitochondrial dysfunction in canine hearts.

The effect of the alpha 1-blocker 4-amino-2-(4-butyryl-hexahydro-1H-1,4-diazepin-1-yl) -6,7-dimethoxy-quinazoline (bunazosin, E-643, Detantol) on reperfusion injury was investigated. 43 anesthetized dogs were divided into two groups: the control group (n = 30) and the bunazosin group (n = 13). 15 min after premedication with physiological saline for the control group, or the alpha 1-blocker bunazosin 0.5 mg/kg for the bunazosin group, the left anterior descending coronary artery was occluded for 15 min and then reperfused for 5 min. Heart mitochondria were prepared from both the normal and reperfused areas. Mitochondria function and their Ca2+ content were measured by polarography and atomic absorption, respectively. Mitochondrial phospholipase activity was measured by high performance liquid chromatography. Nine dogs (30%) of the control group developed reperfusion arrhythmias. None of those pretreated with bunazosin developed arrhythmias. Although mitochondrial dysfunction was observed in the reperfused area in each group, more severe dysfunction was observed in dogs with arrhythmias in the control group. Mitochondrial Ca2+ content in the reperfused area in dogs with arrhythmias increased significantly compared with that in the normal area. Phospholipase activity in the reperfused area in dogs with arrhythmias also increased significantly, but no significant elevation of phospholipase activity was observed in dogs without arrhythmias in both the control and bunazosin groups. These results indicate that reperfusion injury might be closely related to activation of phospholipase linked with alpha 1-adrenergic response.

Coenzyme Q10 and coronary artery disease.

It has been postulated that oxidatively modified low-density lipoprotein (LDL) contributes to the genesis of atherosclerosis. Ubiquinone has been suggested to be an important physiological lipid-soluble antioxidant and is found in LDL fractions in the blood. We measured plasma level of ubiquinone using high-performance liquid chromatography and plasma levels of total cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides in 245 normal subjects (186 males, 59 females) and in 104 patients (55 males, 49 females) who had coronary artery disease not receiving pravastatin and 29 patients (12 males, 17 females) receiving pravastatin. In the normal subjects, the plasma ubiquinone levels did not vary with age. In the patient groups, the plasma total cholesterol and LDL levels were higher and the plasma ubiquinone level lower than in the normal subject group. The LDL/ubiquinone ratio was higher in the patient groups. We found that ubiquinone level, either alone or when expressed in relation to LDL levels, was significantly lower in the patient groups compared with the normal subject group. The 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitor is thought to prevent atherosclerosis, however, it also inhibits ubiquinone production. The present study revealed that HMG CoA reductase inhibitor decreased plasma cholesterol level, and that it did not improve either the ubiquinone level or the LDL/ubiquinone ratio. From these results, the LDL/ubiquinone ratio is likely to be a risk factor for atherogenesis, and administration of ubiquinone to patients at risk might be needed.

Role of the autonomic nervous system in cyclophosphamide-induced heart mitochondrial dysfunction in rats.

This study was designed to clarify mechanisms responsible for cyclophosphamide-induced cardiotoxicity. Rats were divided into 2 groups: the cyclophosphamide group, which received cyclophosphamide (100 mg/kg) intraperitoneally once a day for 4 consecutive days; and the control group, which remained untreated. In each group, myocardial mitochondrial respiratory function, enzymic activities in the respiratory chain, and ventricular acetylcholine and norepinephrine concentrations were measured. In the cyclophosphamide group, decreases in mitochondrial respiratory function and in enzymic activities in the respiratory chain were observed compared with those of the control group. Administration with cyclophosphamide caused increases in acetylcholine and norepinephrine in the myocardium. As an increase in tissue acetylcholine level is reported to be linked with the genesis of myocardial damage, we conclude that cyclophosphamide-induced cardiotoxicity is closely related to mitochondrial dysfunction and that alterations in the autonomic nervous system might be related to this dysfunction.

Effects of denopamine on rat myocardium in comparison with isoprenaline.

The adverse effects of denopamine (TA-064) were investigated on rat myocardium in comparison with those of isoprenaline (isoproterenol). Experiment 1. Rats were treated with isoprenaline (10 mg/kg) or denopamine (10 mg/kg) once by subcutaneous injection. 15 h after drug administration, rat hearts were isolated, and heart mitochondria were prepared. Activities of three portions of electron transport chain (NADH-cytochrome c reductase, succinate-cytochrome c reductase, and cytochrome c oxidase) of mitochondria were measured. In rats treated with isoprenaline, significant decreases in NADH-cytochrome c reductase and cytochrome c oxidase activities were observed. While, in rats treated with denopamine, NADH-cytochrome c reductase activity was not decreased significantly, and decrease in cytochrome c oxidase activity was less than that observed in the isoprenaline group. Experiment 2. Rats were treated with isoprenaline (10 mg/kg) or denopamine (10 mg/kg) by subcutaneous injection once a day for 6 successive days. After the last drug administration, hearts were isolated, and cardiac membranes were prepared. Numbers of beta-adrenergic receptors were measured using 3H-dihydroalprenolol. In rats treated with isoprenaline, a significant decrease in the number of beta-adrenergic receptors was observed. On the contrary, administration of denopamine did not affect significantly the number of beta-adrenergic receptors.

Effect of methylprednisolone on recovery of beta-adrenergic desensitization in rat hearts.

The effects of methylprednisolone (Solu-Medrol, CAS 83-43-2) on isoprenaline (isoproterenol)-induced decreases in the number of beta-receptors and adenylate cyclase activities in rat hearts. Rats were divided into 4 groups: 1. the control group, untreated; 2. the ISPOd group; 3. the ISP7d group, 10 mg/kg of isoprenaline was subsequently injected once a day for 6 successive days, and rats were cervically dislocated 15 h or 7 days after the last isoprenaline injection, respectively; 4. the ISP + MP7d group, 20 mg/kg of methylprednisolone was intraperitoneally injected once a day for 7 successive days following 6 successive days of isoprenaline injection, and rats were cervically dislocated. A significant decrease in the number of beta-receptors was observed (28.9 +/- 4.2 fmol/mg protein) after 6 successive isoprenaline injections compared with the control (41.7 +/- 3.6), and this significant decrease persisted for 7 days (32.6 +/- 5.8). Administration of methylprednisolone accelerated the recovery of beta-receptors (38.4 +/- 5.1) 7 days after the last isoprenaline injection. Adenylate cyclase activities were also decreased by successive isoprenaline treatments (isoprenaline-stimulated adenylate cyclase activity, 13.9 +/- 2.7 pmol/min/mg protein; basal adenylate cyclase activity, 11.2 +/- 1.7) compared with the control (isoprenaline-stimulated, 25.7 +/- 3.7; basal, 18.1 +/- 2.4). Significant decreases in adenylate cyclase activities were observed 7 days after isoprenaline administration (isoprenaline-stimulated, 17.7 +/- 3.9; basal, 14.8 +/- 2.4). Methylprednisolone also accelerated the recoveries (isoprenaline-stimulated, 20.3 +/- 2.9; basal, 17.1 +/- 3.9). These results indicate that methylprednisolone accelerated the recovery of the decrease in beta-adrenergic responsiveness caused by successive administrations of isoprenaline.

Leukotoxin, 9, 10-epoxy-12-octadecenoate: a possible responsible factor in circulatory shock and disseminated intravascular coagulation.

We previously demonstrated that neutrophils biosynthesize the Iinoleate epoxide, 9,10-epoxy-12-octadecenoate, from linoleate and hydroxyl radical. This epoxide is highly cytotoxic, and has been termed leukotoxin. We detected leukotoxin in plasma from two patients with infectious endocarditis and circulatory shock. Maximal leukotoxin levels were 580 nmol/ml and 880 nmol/ml, respectively. The leukotoxin levels were affected by hemodialysis or hemofiltration. Disseminated intravascular coagulation was confirmed by blood coagulation studies in these two patients. Leukocytosis was also observed in these patients. In contrast, leukotoxin was not detected in plasma of normal volunteers. Accordingly, leukotoxin synthesized by recruited neutrophils might be a contributory factor in circulatory shock.

Neutrophil microsomes biosynthesize linoleate epoxide (9,10-epoxy-12-octadecenoate), a biological active substance.

We demonstrated that linoleate epoxide (9,10-epoxy-12-octadecenoate) exists in human burned skin and in lung lavages in patients with adult respiratory distress syndrome. This epoxide shows a highly toxic effect on cellular function. Thus, it was given the name leukotoxin. In this communication, we reveal that neutrophils from various sources such as guinea-pig peritonea and canine or human blood biosynthesize linoleate epoxide from linoleate as a substrate. From the reaction mixture of neutrophils with linoleate, a leukotoxin isomer, 12,13-epoxy-9-octadecenoate, and a 'non-toxic' hydroxy derivative of linoleate, 9-hydroxy-12-octadecenoate, were detected. Biosynthesis of leukotoxin by neutrophils was substantially enhanced by osmotic activation or by a calcium-ionophore, A23187. Microsomes prepared from neutrophils could oxygenate linoleate to leukotoxin in the presence of NADPH. In liver or kidney microsomal reaction mixture, leukotoxin could be detected only in the presence of an epoxide hydrolase inhibitor, epoxytrichloropropane. As biosynthesis of leukotoxin was sensitive to carbon monooxide, it was concluded that cytochrome P-450 dependent monooxygenase is responsible for the biosynthesis. Elucidation of the biosynthesis pathway of leukotoxin might contribute to the treatment of diseases associated with neutrophil recruitment.

Differing time courses between delta lactate and mitochondrial respiration during coronary occlusion and after reperfusion in canine hearts.

The present study was designed to clarify whether or not a difference between arterial and venous lactate (delta lactate) levels is useful for evaluation of mitochondrial function in ischemia-reperfused myocardium. In the first experiment, 12 dogs were divided into 2 groups: 10-min occlusion of the left anterior descending coronary artery (LAD) followed by 10-min reperfusion, or 30-min occlusion followed by 40-min reperfusion, were performed. The lactate levels in the femoral artery and the great cardiac vein were measured enzymatically. delta Lactate was reversed immediately after occlusion. Ten min and 20 min were required for the recovery of delta lactate in the 10-min-occlusion with 10-min-reperfusion, and 30-min-occlusion with 40-min-reperfusion groups, respectively. In the second experiment, 36 dogs were divided into 6 groups: 10-min occlusion of LAD; 10-min occlusion with 10-min reperfusion; 30-min occlusion; and 30-min occlusion with 10-, 20-, or 40-min reperfusion were performed. Mitochondria from normal and occluded or reperfused areas were prepared, and the respiratory function of the mitochondria was measured polarographically. No significant decreases in the mitochondrial function were observed in the 10-min-occlusion, and 10-min-occlusion with 10-min-reperfusion groups. On the other hand, respiratory function of mitochondria was impaired by 30-min occlusion and was not improved by 10- or 20-min reperfusion. Significant recovery in the mitochondrial function was observed after 40-min reperfusion. That is, differing recovery time courses between delta lactate and the mitochondrial function were observed.

Failure of beta-blocking agent to prevent epinephrine-induced myocardial injury in dogs with hypokalemia.

The effect of epinephrine in dogs with hypokalemia was investigated. Injection of epinephrine, 10 micrograms/kg, induced an elevation of serum creatine kinase (CK) activity and histological changes in myocardium of dogs with hypokalemia. The effect of epinephrine was little in dogs with normokalemia. Heart mitochondrial calcium content was elevated in parallel with the decrease in serum K+ in dogs with hypokalemia. Propranolol, a beta-blocker, did not prevent these changes. Since epinephrine increases coronary blood flow, these alterations cannot be ascribed to a reduction in coronary blood flow. It is likely that calcium overload alone, without ischemia, could develop myocardial injury in dogs with hypokalemia, and that beta-adrenergic action is not involved in this pathogenesis.

Acceleration of recovery of mitochondrial function after coronary reperfusion by various coronary dilating drugs in canine hearts.

This study was designed to evaluate whether or not increase in coronary blood flow after reperfusion accelerates the recovery of ischemia-induced mitochondrial damage. Using anesthetized dogs, the left anterior descending coronary artery was occluded for 30 min, followed by 20 min of reperfusion. Five minutes after reperfusion, either physiological saline (n = 9), 0.5 mg/kg of dilazep (n = 7), 0.2 mg/kg of diltiazem (n = 7), or 0.5 mg/kg of nicorandil (n = 8) were administered intravenously. Arterial blood pressure, heart rate, and coronary blood flow were measured throughout the experiment. Twenty minutes after reperfusion, heart mitochondria from normal and reperfused areas were prepared, and mitochondrial function was measured. Significant increase in coronary flow was observed during reperfusion in all drug-treated groups; however, no significant increase was observed in the control group 10 min after reperfusion. Significant hemodynamic changes were not observed in all groups. Mitochondrial function from reperfused areas was recovered significantly in all drug-treated groups, though in the control group mitochondrial dysfunction persisted. Coronary dilative mechanisms of drugs used here differ; however, a similar effect was demonstrated, i.e., administration of a coronary dilator accelerates the recovery of mitochondria after reperfusion. Therefore, it is concluded that coronary flow after reperfusion might be a primary factor in the recovery of ischemia-induced mitochondrial damage.

New two-dimensional, echocardiographically directed pericardiocentesis in cardiac tamponade.

Seventeen patients with cardiac tamponade were treated by pericardiocentesis guided by two-dimensional (2-D) echocardiography and a needle guide. The needle guide used in the present study was designed so that the needle path lies within the center of the scan thickness. Before actual puncture, the mask method was performed in a water bath so that the needle progress avoided injury. The needle progress was monitored continuously in real time on the display throughout the procedure. Immediate relief from acute cardiac tamponade was obtained in all except one patient, who was treated by pericardiotomy because of insufficient drainage. In two patients, second drainage was performed because of reaccumulation of the pericardial effusion. There were no major complications. Nine patients recovered and the other patients died of underlying disease. Accurate and efficient visualization of the needle might allow a safer procedure. We conclude that pericardiocentesis guided by 2-D echocardiography using a needle guide may be a safe and easily applied technique for the management of pericardial effusion.