Release Of CPK Research Articles

Cytoprotective and cytofunctional effect of polyanionic polysaccharide alginate and gelatin microspheres on rat cardiac cells

This study investigated the cyto-functional effect of Alginate-Gelatin microspheres on rat cardiomyoblasts after 7 days. Rat cardiomyoblasts were encapsulated inside Alginate-Gelatin microspheres via application of high voltage rate and dropping in a stirring CaCl2 solution. The swelling rate, biodegradation, and mechanical features were measured. Cell viability was assessed using MTT. Cell membrane integrity was monitored via calculation supernatant SGOT, SGPT, CPK, and LDH. We also measured SOD, GPx, and anti-oxidant capacity. Protein levels of Nrf-2 and PCCG-1α were detected via western blotting. The cyto-functional activity of encapsulated cells was monitored using real-time PCR assay targeting the expression of Connexin-43, α-actinin, and myosin light chain.Data showed suitable biodegradation and swelling rate in Alginate-gelatin microspheres by time. 7-day incubation of rat cells inside microspheres did not exert cytotoxicity compared to control cells (p > 0.05). The release of SGPT, SGOT, CPK, and LDH in encapsulated cells was significantly decreased compared to the control group (p < 0.05). We also found enhanced anti-oxidant capacity and SOD and GPx activity in cells after being-encapsulated inside Alginate-Gelatin microspheres (p < 0.05) coincided with increased Nrf-2 synthesis (p < 0.05) compared to control cells. The expression of Connexin-43, α-actinin, and myosin light chain was significantly up-regulated, showing cyto-functional effect of Alginate-Gelatin microspheres after 7-days.

Role of MAPK phosphorylation in cytoprotection by pro‐vitamin C against oxidative stress‐induced injuries in cultured cardiomyoblasts and perfused rat heart

The reactive oxygen species (ROS) are known to be generated upon post-ischemic reperfusion (I/R) of the heart, and to injure cardiac muscle cells. The hydrogen peroxide-induced mortality of rat cardiomyoblasts H2c9 was markedly inhibited by previous administration with auto-oxidation-resistant pro-vitamin C, the 2-O-phosphorylated derivative (Asc2P) of ascorbic acid (Asc). The cytoprotection was partially counteracted by an inhibitor of MAPK (mitogen-activated protein kinase) kinase (MEK) as shown by DNA strand cleavage assay and mitochondrial dehydrogenase assay. Immunostains indicated that phosphorylated MAPK increased in the hydrogen peroxide-treated cardiomyoblasts, and that this action was moderately inhibited by Asc2P and restored nearly to the initial, pretreatment level by combined administration of the MEK inhibitor and Asc2P. The I/R-induced cell injuries in perfused rat hearts as estimated by extracellular release of the cardiac enzyme CPK were inhibited by 2-O-alpha-glucosylascorbic acid (Asc2G) and Asc, whereas the observed cytoprotection for the cardiomyoblasts was partially counteracted by the MEK inhibitor. The increase in phosphorylated MAPK in I/R-operated hearts was moderately inhibited by pro-vitamin C, but restored nearly to the normal non-operated level by combined administration with the MEK inhibitor. This is in contrast to no alteration in levels of non-phosphorylated MAPK for all the cases examined as shown by Western blots, consistent with results of immunostains for the cardiomyoblasts. The inhibitory effect of the MEK inhibitor on MAPK phosphorylation was, therefore, suggested to counteract the cytoprotective effects of pro-vitamin C via a thorough interruption of the phosphorylated MAPK signaling pathway. This was not true of ROS-related events; the scavenging effects of Asc2G and Asc on hydroxyl radicals generated from I/R-operated heart were not affected by combined administration with the MEK inhibitor, as shown by the spin-trapping DMPO-based ESR method.

Cytoprotection by pro-vitamin C against ischemic injuries in perfused rat heart together with differential activation of MAP kinase family.

The cardiac muscle cells are known to be killed by ischemia-reperfusion (I/R) treatment that produce reactive oxygen species (ROS). We analyzed the function of the autooxidation-resistant pro-vitamin C, 2-O-alpha-D-glucosylated derivative (Asc2G) of ascorbic acid (Asc), in protecting against I/R injury of the heart in rat. The serum release of the intracellular enzyme CPK due to I/R injury decreased upon injection with Asc2G. Out of the mitogen-activated protein (MAP) kinase family members, MAP kinase and JNK underwent the down-regulation in contrast to up-regulation of p38 compared with the I/R-treated control in the absence of Asc2G. These data suggest important roles for differential activation of the MAP kinase family in cytoprotection against I/R injury by Asc2G.

Preliminary observations on the effects of acute infusion of growth hormone on coronary vasculature and on myocardial function and energetics of an isolated and blood-perfused heart.

Recent studies have shown that growth hormone (GH) deficiency may deteriorate post-ischemic myocardial reperfusion damage. Furthermore, GH has been reported to be a promising therapeutic option in the treatment of chronic myocardial dysfunction. However, the exact mechanisms of action of GH on the cardiovascular system, particularly in the acute setting, are still unclear. The aim of our study consisted of monitoring the acute effects of GH infusion on isolated blood-perfused rabbit heart according to dose-response pattern and during ischemic conditions to test its anti-ischemic property. Seven blood-donors perfused isolated hearts were used as experimental model. The mechanical and metabolic data of the isolated organs were continuously monitored. Under aerobic conditions, dose-response curves were initially tested after intracoronary infusion of GH at increasing dosages (1, 2, 3 mg/l). After a stabilization period, the effects of GH infusion (5 mg/kg) administered 30 minutes prior to acute global myocardial ischemia (30 minutes) were also investigated. At the doses tested, GH did not induce any changes either in the developed or in the diastolic pressures of the isolated organ. However, transient reduction of the coronary perfusion pressure was observed at the dosage of 3 mg/l. During the ischemia/reperfusion study, at the dosages used in this study, GH did not modify either the degree of stunning in the early reperfusion or the recovery of the developed pressure at the end of reperfusion. In addition, GH did not prevent either the increase of diastolic pressure during ischemia or the release of lactate and CPK during reperfusion. Tissue content of high-energy phosphates was also not changed by GH infusion. In our experimental model, acute GH infusion did not reduce the ischemic/reperfusion damage of the myocardium. However, GH transiently induced coronary vasodilation without modifying the myocardial contractility. Acute effects of GH appear, therefore, to predominantly relate to vascular dilation suggesting that the effects on myocardial contractility may require long-lasting intake being likely linked to enhancement of specific protein synthesis or gene expression of cardiac myocytes.

The blood perfused isolated heart: characterization of the model.

We have characterized the aerobic blood-perfused isolated heart model evaluating the hemodynamics and metabolism of both the blood donor animal and the isolated organ. Anaesthesia of the blood donor with sodium pentobarbital (30 mg/kg) increases arterial concentration of non esterified fatty acids (NEFA) from 80 +/- 6 to 452 +/- 70 microM; p < 0.01. Injection of 1,000 U/kg heparin causes a second significant increase from 452 +/- 70 to 1012 +/- 104 microM; p < 0.01. Insertion of the perfusion circuit, without the isolated heart, causes a reduction in blood pressure of the blood donor and a significant increase in norepinephrine from 277 +/- 44 to 634 +/- 130 pg/ml; p < 0.05. Two hours of aerobic perfusion of the isolated heart inserted in the perfusion circuit, decreases arterial pressure of the blood donor with a concomitant increase of plasma norepinephrine from 475 +/- 150 to 841 +/- 159 pg/ml; p < 0.05. Developed pressure, oxygen consumption, glucose and NEFA uptake of the isolated heart remain constant during two hours of aerobic perfusion, NEFA being the preferred substrate. Tissue content of high energy phosphates at the end of the perfusion is high and similar to that observed "in vivo". Despite this, there is a release of lactate and CPK from the isolated heart. We conclude that: 1) the model allows accurate measurement of hemodynamics and metabolism of both the isolated heart and the blood donor animal; 2) the perfusion procedure modifies the substrates concentration of the blood donor animal which, in turn, results in the preferential NEFA utilization of the isolated heart. These changes do not affect the functional parameters of the perfused heart.

The effect of two handling and slaughter systems on skin damage, meat acidification and colour in pigs

In order to minimize the high proportion of carcass and meat quality defects recorded in commercially slaughtered pigs, the optimum handling, stunning and bleeding-out conditions must be implemented. In this study improvements in pig handling resulted in the elimination of electric goading within the raceways, which reduced the skin blemish score by 50%. Furthermore, the application of higher stunning voltage (200 V) and the immediate bleeding-out in the prone position improved the post-mortem acidification rate in the Longissimus thoracis (LT) and Semimembranosus (SM) muscles. This resulted in a sharp reduction of the PSE incidence in both muscles. A positive effect on muscle metabolism was also showed by the lower release of CPK into the bloodflow. These results show that, under commercial conditions, the design of slaughter handling systems and the slaughter procedures can have an effect on skin damage and on the quality of the pig meat.

Mechanism of Polyamine Toxicity in Cultured Cardiac Myocytes

The goal of this study was to investigate the mechanism of polyamine-mediated injury to the cardiac myocytes isolated from neonatal rat hearts. The myocytes, cultured in Dulbecco's minimal essential medium–1% foetal calf serum (FBS), were exposed to spermidine or spermine. The toxicity to myocytes was determined by (a) increased release of creatine kinase (CPK) into the media and (b) decline in cell viability or functional activity. Spermidine, above 10 μ m, increased the release of CPK into media, decreased cell viability and decreased the functional activity of the myocytes. The FBS exhibited polyamine oxidase activity and semicarbazide-sensitive amine oxidase activity. Aminoguanidine, MDL72,527 or semicarbazide, are the inhibitors of amine oxidases, polyamine oxidase (PAO) and semicarbazide-sensitive amine oxidase (SSAO), respectively. The addition of these inhibitors to the medium protected the myocytes from spermidine toxicity. To determine whether myocyte PAO is involved in polyamine toxicity, we used horse serum that contained high SSAO activity and negligible PAO activity. The myocyte extracts had negligible SSAO activity but high PAO activity. When myocytes were cultured in horse serum in lieu of FBS, spermine caused toxicity at above 100 μ m. In horse serum, MDL72,527 and semicarbazide protected the myocytes from spermine toxicity. These observations show that extracellular amine oxidases and myocyte PAO are significant in mediation of polyamine toxicity.

Effects of felodipine on the ischemic heart: insight into the mechanism of cytoprotection.

To assess whether the administration of felodipine protects the myocardium in a dose-dependent manner against ischemia and reperfusion, isolated rabbit hearts were infused with three different concentrations of felodipine: 10(-10), 10(-9), and 10(-8) M. Diastolic and developed pressures were monitored; coronary effluent was collected and assayed for CPK activity and for noradrenaline concentration; mitochondria were harvested and assayed for respiratory activity; and ATP production and calcium content and tissue concentration of ATP, creatine phosphate (CP), and calcium were determined. The occurrence of oxidative stress during ischemia and reperfusion was also monitored in terms of tissue content and release of reduced (GSH) and oxidized (GSSG) glutathione. Treatment with felodipine at 10(-10) and 10(-9) M had no effect on the hearts when perfused under aerobic conditions, whilst the higher dose reduced developed pressure from 57.7 +/- 2.6 to 30.0 +/- 2.6 mmHg (p < 0.01). On reperfusion treated hearts recovered better than the untreated hearts with respect to left ventricular performance, replenishment of ATP and CP stores, and mitochondrial function. Recovery of developed pressure was 100% at 10(-8) M, 55% at 10(-9) M, and 46% at 10(-10) M. The reperfusion-induced tissue and mitochondrial calcium overload, release of CPK and noradrenaline, and oxidative stress were also significantly reduced. The effects of felodipine were dose dependent. Felodipine inhibited the initial rate of ATP-driven calcium uptake but failed to affect the initial rate of mitochondrial calcium transport. It is concluded that felodipine infusion provides dose-dependent protection of the heart against ischemia and reperfusion. Because this protection also occurred at 10(-9) M and 10(-10) M in the absence of a negative inotropic effect during normoxia and of a coronary dilatory effect during ischaemia, it cannot be attributed to an energy-sparing effect or to improvement in oxygen delivery. From our data we can envisage two other major mechanisms-(1) membrane protection and (2) reduction in oxygen toxicity. The ATP-sparing effect occurring at 10(-8) M is likely to be responsible for the further protection.

In vitro evaluation of phosphate, bicarbonate, and Hepes buffered storage solutions on hypothermic injury to immature myocytes.

In this study we evaluated cardiac myocyte viability and function under hypothermic conditions using three types of buffer solutions: phosphate buffer solution (PBS), Krebs-Henseleit bicarbonate buffer solution (KHB), and Hepes buffered minimum salt solution (MSS). As a control, normal saline solution (NSS) was used. Cardiac myocytes were isolated from neonatal rat ventricles. Myocytes (12.5 x 10(5) myocytes/culture flask) were then incubated at 4 degrees C for 6, 12, 18, and 24 hours in various buffer solutions. After each incubation time, CPK and LDH were measured. The myocytes were then incubated for an additional 24 hours at 37 degrees C to evaluate the recovery of the myocyte beating rate. Group MSS had a significantly better beating rate recovery than group NSS (control) after 18 hours (MSS, 32.7%, NSS, 0.0% of control; i.e., beating rate prior to hypothermic incubation). In contrast, group KHB showed a significantly lower recovery ratio than group NSS at 12 hours (41.0%, 78.8%, respectively), and the lowest recovery was observed in group PBS beginning at 6 hours of hypothermic incubation (27.6%). Group MSS significantly suppressed the release of CPK and LDH compared to group NSS at 24 hours (MSS, 246.7 and 440.2 mIU/flask; NSS, 369.7 and 821.3 mIU/flask, respectively). In contrast, groups PBS and KHB showed significantly increased CPK and LDH levels compared to group NSS after 12 hours (PBS, 388.6 and 721.4 mIU/flask; KHB, 340.5 and 540.5 mIU/flask; NSS, 91.5 and 222.7 mIU/flask, respectively). In conclusion, Hepes buffer has cytoprotective characteristics that may be suitable for long-term hypothermic preservation of immature myocardium compared to phosphate or bicarbonate buffer.

Effect of serum concentration on hypothermic preservation of cardiac myocytes isolated from neonatal rat ventricle.

The purpose of the present study was to evaluate the functional and biochemical effects of serum concentrations on hypothermic preservation of cardiac myocytes. Myocytes were isolated from neonatal rat ventricles and cultured for 4 days, and then incubated for 24 hrs at 4 degrees C in media containing 0, 2, 5, 10, and 20% fetal calf serum (FCS). The myocytes were then cultured for an additional 24 hrs at 37 degrees C to evaluate the recovery of myocyte beating rate. The recovery ratio of myocyte beating rate after hypothermic incubation was 25.3 +/- 14.2 percent of control in the serum-free, 33.0% in 2% FCS, 30.7% in 5% FCS, 22.3% in 10% FCS, and 24.3% in 20% FCS groups. Serum-free, 10% and 20% FCS groups had lower recovery ratios compared to the other two groups. The release of CPK and LDH after hypothermic incubation were similar in the serum-free, 2% and 5% FCS groups, however, significant increases were observed for the 10% and 20% FCS groups. It is suggested that fetal calf serum at high concentrations (> 10%) might be injurious to immature myocardium under hypothermic preservation, and that the optimum concentration of FCS is two percent or less.

Protection of Cardiac Myocytes from Hypothermic Injury by Cardiac Fibroblasts Isolated from Neonatal Rat Ventricle

In this study, we evaluated the functional and bio-chemical effects of cardiac fibroblasts (CFs) on cardiac myocytes (CMs) incubated under hypothermic conditions. CMs and CFs were isolated from neonatal rat ventricles and cultures of myocytes only or myocytes in coculture with CFs were established. A CM anti CF concentration of 2.5 ×105 cells/ml was chosen and the optimum proportion of CF was determined to be 33% (ml CM:ml CF) as follows: 6:0 (group C-a), 4:0 (group C-b), 4:2 (group M-F). On the fourth day of culture, cells were incubated at 4?C for 6, 12, 18, 24, 36 and 48 hr. After each incubation, creatine phosphokinase ((PK) and lactate dehydrogenase (LDH) were measured in the medium, and then the cells were cultured for an additional 24 hr at 37°C to evaluate the recovery of the CM contracting rate. In groups C-a and C-b (n = 6 each), the recovery ratio of CM contracting rate decreased at 18 hr (C-a, 59.0; C-b, 55.6% of control; i.e., contracting rate prior to hypothermic incubation), reaching null levels at 48 hr. However, group M-F (n = 6) showed a significantly increased recovery, at 18 hr (95.7%, P < 0.05; at 48 hrs, 27.6%). Release of CPK and LDH in groups C-a and C-b increased gradually by 24 hr and showed a marked increase at48 hr (C-a, 114.3 × 10-2, 194.2 × 10-2; C-b, 81.6 × 10-2, 118.6 × 10-2 IU flask, respectively). In addition, the enzyme values of each control group at each incubation time correlated with the myocyte cell number per flask. In contrast, the levels of CPK and LDH in group M-F were significantly lower at 18 hr, and the greatest difference was observed at 48 hr (CPK, 21.6 × 102; LDH, 47.3 × 10-2; P < 0.001 vs group C-b). In conclusion, the presence of CFs protects CMs from hypothermic injury, which suggests that fibroblasts may play an important role in preserving cardiac myocyte function in the neonatal period.

In vitro evaluation of diltiazem on hypothermic injury to immature myocytes

The purpose of the present study was to evaluate the functional and biochemical effects of diltiazem (DTZ) on cardiac myocytes incubated under hypothermic conditions. Cardiac myocytes were isolated from neonatal rat ventricles and cultured for 4 days with MCDB 107 medium. Then, myocytes (12.5 x 10(5) myocytes/flask) were incubated at 4 degrees C for 24 hours in media with or without DTZ at concentrations of 0 M (group C), 10(-7) M (Group D1), 10(-6) M (group D2), 10(-5) M (group D3), or 10(-4) M (group D4). After 24 hours at 4 degrees C, CPK and LDH were measured. The myocytes were then cultured for 24 hours at 37 degrees C to evaluate the recovery of the myocyte beating rate. In group C (n = 7), the recovery ratio of the myocyte beating rate was 29.9% of control (beating rate prior to hypothermic incubation). Groups D1 and D2 (n = 7 each) had approximately the same recovery ratios as group C (24.0% and 24.7%, respectively); however, groups D3 and D4 (n = 7 each) showed no beating rate recovery. Release of CPK and LDH in group C was 112.3 mIU/flask and 457.4 mIU/flask, respectively. Groups D1 and D2 showed no significant differences in both enzymes compared to group C. However, the levels of CPK were significantly higher in group D4 (203.3, p < 0.05), and LDH levels were significantly higher in groups D3 and D4 (669.3, p < 0.05; 883.4, p < 0.02). In conclusion, DTZ showed no protective effects on hypothermic injury to immature cardiac myocytes; moreover, it accelerated cellular injury at the concentrations of 10(-5) and 10(-4) M both functionally and biochemically. Therefore, diltiazem may not be suitable for cardiac preservation during the neonatal period.

Effect of lacidipine on ischaemic and reperfused isolated rabbit hearts.

Lacidipine is a new developed dihydropyridine calcium-antagonist, showing a slow onset and long lasting-selective activity. To assess whether the administration of lacidipine protects the myocardium in a dose-dependent manner against ischaemia and reperfusion, isolated rabbit heart were infused with three different concentrations of lacidipine: 10(-10); 10(-9); 10(-8) M. Diastolic and developed pressures were monitored; coronary effluent was collected and assayed for CPK activity and for noradrenaline concentration; mitochondria were harvested and assayed for respiratory activity, ATP production and calcium content and tissue concentration of ATP, creatine phosphate (CP) and calcium were determined. Occurrence of oxidative stress during ischaemia and reperfusion was also monitored in terms of tissue content and release of reduced (GSH) and oxidized (GSSG) glutathione. Treatment with lacidipine at 10(-10) and 10(-9) M had no effects on the hearts when perfused under aerobic condition, whilst the higher dose reduced developed pressure of 36%. The ischaemic-induced deterioration of mitochondrial function was attenuated. On reperfusion treated hearts recovered better than the untreated hearts with respect to left ventricular performance, replenishment of ATP and CP stores and mitochondrial function. The reperfusion-induced tissue and mitochondrial calcium overload, release of CPK and of noradrenaline and oxidative stress were also significantly reduced. The effects of lacidipine were dose-dependent. The lower concentration (10(-10) M) failed to modify ischaemic and reperfusion damage. The dose of 10(-9) M was cardioprotective, but the best effect was found at 10(-8) M. It is concluded that lacidipine infusion provides a dose dependent protection of the heart against ischaemia and reperfusion. Because this protection occurred also at 10(-9) M, in the absence of negative inotropic effect during normoxia and of a coronary dilatory effect during ischaemia, it cannot be attributed to an energy sparing effect or to improvement of oxygen delivery. From our data we can envisage two other major mechanism: -1) membrane protection -2) reduction of oxygen toxicity. The ATP sparing effect occurring at 10(-8) M is likely to be responsable for the further protection.

Evaluation of a new calcium containing cardioplegic solution in the isolated rabbit heart in comparison to a calcium-free, low sodium solution

Isolated perfused rabbit hearts were studied to compare the effects of 3 hour ischemic arrest following either calcium-free or calcium-containing cardioplegia, on the recovery of isovolumic function of the left ventricle, coronary flow, release of creatine phosphokinase and myocardial water content. The hearts perfused with the calcium-containing solution (Ca 0.5 mmol/L) showed better recovery of the developed pressure in the left ventricle, and its first derivative and compliance. Coronary flow at a constant perfusion pressure was better restored during reperfusion in the hearts with calcium-containing solution. The release of less CPK and a lower water content were also observed in the hearts reperfused with calcium-containing solution. We concluded that calcium-containing cardioplegic solution with a high concentration of magnesium (10 mmol/L) was superior to calcium-free solution for myocardial protection.

Oxygen free radical-mediated heart injury in animal models and during bypass surgery in humans. Effects of alpha-tocopherol.

There is evidence that oxygen free radicals play a role in myocardial ischemic and reperfusion injury. We investigated the effect of ischemia and reperfusion on glutathione status. Reperfusion after prolonged ischemia (60 min) induced an important release of reduced (GSH) and oxidized (GSSG) glutathione, concomitant with an increase of tissue GSSG and no recovery of mechanical function, indicating that reperfusion results in oxidative stress. These alterations are associated with tissue and mitochondrial calcium accumulation, loss of mitochondrial function, and membrane damage. We also determined the arteriocoronary sinus difference for GSH and GSSG of 16 CAD patients undergoing coronary artery bypass. Patients were divided in two groups according to the length of clamping period: 25 +/- 2 min (group 1), and 55 +/- 6 min (group 2). In group 1, reperfusion resulted in a transient release of GSH, GSSG, CPK, and lactate, with return to preclamping values in 10 minutes. In group 2, reperfusion determined a sustained and pronounced release of GSH, GSSG, CPK, and lactate during declamping, suggesting the occurrence of an oxidative stress. Using an in vitro model, administration of alpha-tocopherol bound with albumin showed protection of mitochondrial function, improved recovery of contraction, and reduced oxidative stress during reperfusion.

No evidence for an increased lipid peroxidation during reoxygenation in Langendorff hearts and isolated atria of rats

Rat left atria or Langendorff hearts were kept at 37°C and stimulated at a rate of 3.33 Hz. They were subjected to hypoxia (deprivation of oxygen) or ischemia (deprivation of oxygen and glucose + acidosis + increased extracellular potassium concentration) for 15 min or 1 h and subsequent reoxygenation for 5 or 15 min. Tissue concentrations of proteins, reduced and oxidized glutathione and conjugated dienes were measured at the end of the experiment. Hypoxia and ischemia decreased the excitability and contractility of the preparations and caused contracture. These effects were partly reversible during reoxygenation. However, in Langendorff hearts reoxygenation caused an increased release of CPK, LDH and glutathione into the perfusion fluid. Ischemia and reoxygenation in atria lowered the tissue concentration of reduced glutathione and increased its oxidized form. Similar changes were seen in atria and Langendorff hearts when oxygen radical production was accelerated by hypoxanthine and xanthine oxidase. No treatment raised significantly the concentration of conjugated dienes. These results seem to exclude an important role of an increased lipid peroxidation for reperfusion injury of isolated heart preparations.

Protective effects of captopril and enalapril on myocardial ischemia and reperfusion damage of rat

The protective effect of angiotensin-converting enzyme inhibitors (ACEI) on myocardial ischemia and reperfusion damage was estimated in rat hearts, both in vivo and in vitro. Enalapril 2.5 mg/kg ip pretreatment at 24 and 5 h before coronary occlusion, significantly blunted the rise of CPK (445 +/- 151 vs 649 +/- 244 mu/ml, P less than 0.05) and improved electrocardiogram (ECG) 8 h after coronary occlusion. In global ischemia and reperfusion ex vivo, enalapril improved contractility (0.9 +/- 0.2 vs 0.3 +/- 0.3 g, P less than 0.05) and coronary flow (15.6 +/- 3.3 vs 11.9 +/- 3.1 ml/min/g, P less than 0.05), shortened significantly the duration of reperfusion arrhythmia (3.1 +/- 2.7 vs 9.7 +/- 8.1 min, P less than 0.05). In Langendorffs heart, captopril remarkably preserved force of contraction (2.1 +/- 0.4 vs 1.4 +/- 0.4 g, P less than 0.01) and coronary flow (2.7 +/- 0.5 vs 3.6 +/- 0.9 ml/min/g, P less than 0.05) in segmental infarction deteriorated by angiotensin I. Captopril 10(-5) M infusion reduced the release of CPK (435 +/- 112 vs 640 +/- 123 mu/min coronary flow, P less than 0.05). This action was almost completely abolished by pretreating and infusing with indomethacin. As a positive control, prostacyclin 5 X 10(-7) M infusion further reduced the release of CPK to 330 +/- 77 mu/min. It is concluded that angiotensin-converting enzyme inhibitor can protect both myocardial ischemia and reperfusion damage in rat hearts. The mechanism of protection was ascribed to reduced production of angiotensin II by ACE inhibition and increased prostacyclin release in the myocardium.

Effects of thiopental on cardiac energy metabolisms in postischemic reperfusion in rat.

In experiments on isolated rat heart lung preparation, the effects of thiopental on myocardial metabolisms in postischemic reperfusion were evaluated with intramyocardial high energy phosphates, lactate, pyruvate and glycogen. The release of CPK in the perfusate blood was also measured at the end of reperfusion. After 10 min perfusion, hearts were made globally ischemic for 8 min and reperfused for 12 min. Large dose of thiopental (100 microg/ml) reduced the energy charge and glycogen content. Reperfusion with an anesthetic dose of thiopental (10 microg/ml) resulted in an exacerbation of the CPK release. Protection by thiopental during ischemia was not observed and its high dose may be harmful.

Oxygen-mediated myocardial damage during ischameia and reperfusion: Role of the cellular defences against oxygen toxicity

The possibility that myocardial ischaemia alters the defence mechanisms against oxygen toxicity has been investigated. Ischaemia was induced in isolated, perfused rabbit hearts by reducing coronary flow from 25 ml/min to 1 ml/min for 90 min. Two different degrees of ischaemic damage have been achieved using either spontaneously beating or electrically stimulated hearts. The effects of post-ischaemic reperfusion were also followed for 30 min. Tissue activity of superoxide dismutase (SOD), glutathione peroxidase and reductase (GPD and GRD) have been determined together with tissue content of reduced and oxidized glutathione (GSH and GSSG) and of protein SH groups. The changes in myocardial ATP and CP content and release of CPK and of GSH and GSSG were also determined. Systolic and diastolic pressures were continuously monitored. In the spontaneously beating hearts ischaemia induced a reduction of tissue GSH and protein SH groups. On reperfusion there was a recovery of mechanical function, a transient release of GSH into the coronary effluent and an increase of tissue GSH. In the paced hearts, ischaemia resulted in 50% reduction of mitochondrial SOD activity together with a reduction of tissue GSH and protein SH groups. Reperfusion induced a massive release of CPK and of GSH and GSSG, a further reduction of tissue GSH concomitant with an increase of GSSG and no recovery of mechanical function. GPD and GRD activity were not affected by ischaemia and reperfusion. These data indicate that severe ischaemia induces a reduction of the protective mechanisms against oxygen toxicity.

Reduced tolerance to reperfusion-associated injury in hearts from myopathic hamsters.

This study was done to evaluate the response of myopathic hearts from dystrophic hamsters to 30 minutes of ischemia followed by 30 minutes of reperfusion. Hearts from male and female normal animals recovered 77 +/- 6% and 64 +/- 5% of their contractile force respectively following reperfusion whereas only 34 +/- 8% (male) and 34 +/- 7% (female) recovery was seen in myopathic hearts (P less than 0.01). Substantial sustained contractures were observed during reperfusion in hearts from dystrophic animals irrespective of gender whereas none were seen with control hearts. Reperfusion produced a rapid release of CPK that peaked at 5 minutes (approximate coronary effluent concentration of 40 mU/ml) and remained elevated for the reperfusion duration. Peak CPK values for normal hearts were reached at 10 minutes following reperfusion, were significantly lower from the myopathic hearts and returned to near control levels at the end of the 30 minute reperfusion period. Reducing Ca2+ in the perfusion medium by up to 80% or perfusing the hearts with the Ca2+-channel blocker verapamil produced no beneficial effects. Changes in the above parameters produced by ischemia or heart rate alterations throughout the perfusion sequence were not different between normal and myopathic hearts. This study shows a sensitivity of myopathic hearts that is manifested during reperfusion. Possible mechanisms for this reduced tolerance are discussed.