The effect of post-ischemic hypothermia following repetitive cerebral ischemia in gerbils

Repetitive ischemia may result in more severe damage than a single similar duration insult. Inter-ischemic hypothermia significantly decreases this damage. It is unclear if protection would be evident if cooling was delayed until after the repeated insults. In this study, we evaluated the effects of 3 h of mild cooling (34-35 degrees C) beginning immediately after the third insult of ischemia, 0.5 h after the third insult and 1 h after the third insult in a gerbil model of repetitive ischemia. Neuronal damage was assessed in the cerebral cortex (CTX), hippocampus (CA1, CA4), striatum (STR), thalamus (THL), medial geniculate nucleus (MGN), and the substantia nigra reticulata (SNr). A '4-point' damage scale was used and evaluation was done in a blinded way. Group comparisons were done using the Mann-Whitney U-test for significance between the control and hypothermic groups. Immediate hypothermia after the third ischemic insult produced a significant protection in the CTX (P < 0.05), hippocampus (CA1 and CA4, P < 0.01), STR (P < 0.001), SNr (P < 0.01), MGN (P < 0.01) and THL (P < 0.01). Cooling at 0.5 and 1 h after the third insult produced no protection when compared to ischemic controls. The window of opportunity with hypothermia is narrow in repetitive ischemia. To be effective, therapy must be initiated as soon as possible after ischemic insults.

Neuronal protection with superoxide dismutase in repetitive forebrain ischemia in gerbils

The underlying mechanism for severe damage with repetitive ischemia is not fully understood. Because of prolonged periods of reperfusions between the brief insults, we speculated that the severe damage may be secondary to excessive generation of oxygen free radicals. In this study we tested the efficacy of peg-superoxide dismutase (SOD) in a model of repeated ischemia in gerbils. Superoxide dismutase (SOD) or vehicle (saline) was delivered through osmotic pumps into the lateral ventricles continuously from the onset of the insult until the gerbils were sacrificed 6 days later. Three doses of SOD were used in the experiments (110, 150, and 190 units per microliter). Damage was assessed using a 0-4 point scoring system and statistical comparisons were done using the Mann-Whitney U-test. There was significant protection in the hippocampus (p < 0.05), striatum (p < 0.001), and substantia nigra reticulata (p < 0.05) in the lowest dose SOD-treated group (110 units per microliter). Animals treated with 150 units showed lesser (but significant) protection in the thalamus, medial geniculate nucleus, and striatum. In the animals treated with the higher dose of SOD (190 units per microliter), the extent of damage was no different than vehicle-treated controls in the cortex, striatum, and hippocampus. Compared to controls, neuronal damage was, however, significantly more severe in the medial geniculate nucleus and the thalamus in the high-dose SOD-treated animals (p < 0.05). Our experiments suggest that the SOD may have a small therapeutic window. Higher doses may either have no neuroprotective effects or may be harmful.

Molecular interaction between cAMP and calcium in calmodulin-dependent cyclic nucleotide phosphodiesterase system

The second messenger molecules cAMP and Ca2+ regulate a large number of eukaryotic cellular events. cAMP acts on protein kinases, and Ca2+ works through a ubiquitous calcium-binding protein, calmodulin. The 2 systems are not independent, however, but interact in several important fashions. These interactions can be demonstrated by calmodulin-dependent phosphodiesterase. The bovine heart calmodulin-dependent phosphodiesterase can be phosphorylated by cAMP-dependent protein kinase, resulting in a decrease in the enzyme's affinity for calmodulin. The phosphorylation of calmodulin-dependent phosphodiesterase is blocked by Ca2+ and calmodulin, and reversed by the calmodulin-dependent phosphatase (calcineurin). The dephosphorylation is accompanied by an increase in the affinity of the phosphodiesterase for calmodulin. Results from this study suggest that the activity of this phosphodiesterase is precisely regulated by cross-talk between Ca2+ and cAMP signalling pathways.

Protective effects of lazaroids against oxygen-free radicals induced lysosomal damage

Lipid peroxidation of membranes by oxygen free radicals has been implicated in various disease states. Different antioxidants and iron chelators have been used to reduce lipid peroxidation. Lazaroids have been used for the acute treatment of central nervous system disorders such as trauma and ischemia wherein lipid peroxidative processes take place. In this study we evaluated the effect of lazaroids (U-78518F and U-74389F) on the release of acid phosphatase activity and formation of malondialdehyde (MDA) in rat liver lyosomes subjected to exogenously generated oxygen free radicals. There was a significant increase in the acid phosphatase release and MDA formation in the presence of oxygen free radicals. This was prevented by both the lazaroids. In a separate study the effect of lazaroid U-74389F was seen on the zymosan-stimulated polymorphonuclear (PMN) leukocyte-derived chemiluminescence. The PMN leukocyte chemiluminescent activity was attenuated by the lazaroid in a dose-dependent manner. These studies suggest that lazaroids may inhibit lipid peroxidation and stabilize the membrane.

Oxygen free radicals and cardiac depression

The present investigation deals with the in vivo effects of oxygen free radicals (OFRs) in the absence and presence of scavengers of OFRs (superoxide dismutase, SOD, and catalase) on the cardiac function and contractility and with the in vitro effects of exogenous OFRs and various pH and pO2 on the release of acid hydrolases from dog myocardial lysosomes. The hemodynamic measurements were made before and at various intervals after administration of OFRs for up to 2 h. Xanthine plus xanthine oxidase (X-XO) and opsonized zymosan were used to generate OFRs. Oxygen free radicals produced a decrease in the cardiac function and indices of myocardial contractility. SOD alone or in combination with catalase tended to protect the cardiac function against the deleterious effects of OFRs. There was about a threefold increase in the release of cathepsin D activity in vitro from the lysosomes in the preparations treated with X-XO as compared to those without such treatment. The presence of SOD prevented the release of cathepsin D from the lysosomes. The changes in pH (4.5, 5.5, 6.0, 6.5, 7.4, 8.0) alone did not cause any increase in the enzyme release. However, the presence of OFRs at each pH resulted in a similar increase (about threefold) in the release of cathepsin D. Similarly the changes in pO2 alone did not cause the release of cathepsin D, but there were marked increases in the release of cathepsin D at each pO2 in the presence of OFRs. These data indicate that it is the oxygen free radicals and not the alterations in pH or pO2 that are primarily responsible for the release of lysosomal hydrolases.(ABSTRACT TRUNCATED AT 250 WORDS)

Superoxide dismutase, catalase, and U78517F attenuate neuronal damage in gerbils with repeated brief ischemic insults

Repeated ischemic insults at one hour intervals result in more severe neuronal damage than a single similar duration insult. The mechanism for the more severe damage with repetitive ischemia is not fully understood. We hypothesized that the prolonged reperfusion periods between the relatively short ischemic insults may result in a pronounced generation of oxygen free radicals (OFRs). In this study, we tested the protective effects of superoxide dismutase (SOD) and catalase (alone or in combination), and U78517F in a gerbil model of repetitive ischemia. Three episodes (two min each) of bilateral carotid occlusion were used at one hour intervals to produce repetitive ischemia. Superoxide dismutase and catalase were infused via osmotic pumps into the lateral ventricles. Two doses of U78517F were given three times per animal, one half hour prior to each occlusion. Neuronal damage was assessed 7 days later in several brain regions using the silver staining technique. The Mann-Whitney U test was used for statistical comparison. Superoxide dismutase showed significant protection in the hippocampus (CA4), striatum, thalamus and the medial geniculate nucleus (MGN). Catalase showed significant protection in the striatum, hippocampus, thalamus, and MGN and the substantia nigra reticulata. Combination of the two resulted in additional protection in the cerebral cortex. Compared to the controls, there was little protection in a dose of 3 mg/kg of U78517F. There was significant protection with a dose of 10 mg/kg in the hippocampus (CA4), striatum, thalamus, medial geniculate nucleus and the substantia nigra reticulata.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypothyroidism protects the brain during transient forebrain ischemia in gerbils

The mechanisms by which brain cells die after brief episodes of cerebral ischemia are not fully understood. In certain brain regions this damage may not be apparent for days. Hypothyroidism is known to decrease cerebral metabolism. We postulated that this slowing in cerebral metabolism may be neuroprotective after transient cerebral ischemia. To test this hypothesis, a total of 10 gerbils had thyroidectomies performed 2 weeks prior to ischemia. Six gerbils served as euthyroid controls. All animals were exposed to 5 min of transient ischemia and sacrificed 7 days after the insult. Silver degeneration staining was used for histological evaluation. Hippocampal damage [subiculum (P < 0.001), CA1 (P = 0. < .001), CA3 (P < 0.05), and CA4 (P < 0.001)] was significantly less in the hypothyroid animals. There was also significantly less damage in the cerebral cortex (P < 0.05) and thalamus (P < 0.05) in the hypothyroid animals. The exact mechanism of this protection is not fully understood but could be secondary to a decrease in the metabolic activity, or a reduced generation of free radicals (as is seen with protection from ischemia in kidney and liver under hypothyroid conditions). Further studies are required in order to gain a better understanding of the protective effects of hypothyroidism on cerebral ischemia.

Purification and properties of bovine spleen N-myristoyl-CoA protein:N-myristoyltransferase

Myristoyl-CoA:protein N-myristoyltransferase (NMT) catalyzes the addition of myristate to the amino-terminal glycine residue of a number of eukaryotic proteins. In this report, a simple and rapid purification as well as the properties of this enzyme from bovine spleen is described. Using combination of ammonium sulfate precipitation, chromatography on SP-Sepharose fast flow, phenyl-Sepharose CL-4B, DEAE-Sepharose CL-6B, and Superose 12 (HR/30) gel filtration fast protein liquid chromatography, the enzyme was purified 1475-fold with a high yield. Under native conditions, the enzyme exhibited an apparent molecular mass of 58 kDa, whereas under denaturing conditions the enzyme represented an apparent molecular mass of 50 kDa, suggesting that spleen NMT is a monomeric protein. The NMT activity could be greatly activated to severalfold with the use of Tris-HCl buffer. Kinetic properties indicated that spleen NMT had an apparent low Km for pp60src and myristoylated alanine-rich C kinase substrate as compared with cAMP-dependent protein kinase and the M2 gene segment of reovirus type 3-derived peptides. Bovine spleen NMT was potently inhibited in a concentration-dependent manner by NIP71 (a bovine brain NMT inhibitory protein) with a half-maximal inhibition of 0.816 microgram/ml. Results of this study along with the existing knowledge on NMT indicate that the activity of enzyme resides in a single polypeptide chain of molecular mass between 50 and 68 kDa.

Characterization of calmodulin-dependent cyclic nucleotide phosphodiesterase isoenzymes

Calmodulin-dependent phosphodiesterase (CaMPDE) is one of the key enzymes involved in the complex interactions which occur between the cyclic-nucleotide and Ca2+ second-messenger systems. Calmodulin-dependent phosphodiesterase exists in different isoenzymic forms, which exhibit distinct molecular and/or catalytic properties. The kinetic properties suggest that the 63 kDa brain isoenzyme is distinct from the brain 60 kDa and heart and lung CaMPDE isoenzymes. The CaMPDE isoenzymes of 60 kDa from brain, heart and lung are regulated by calmodulin, but the affinities for calmodulin are different. At identical concentrations of calmodulin, the bovine heart CaMPDE isoenzyme is stimulated at a much lower Ca2+ concentration than the bovine brain or lung isoenzymes. The bovine lung CaMPDE isoenzyme contains calmodulin as a tightly bound subunit, so that a change in calmodulin concentration had no effect on the [Ca2+]-dependence of activation of this isoenzyme. These observations are consistent with the notion that differential regulation by calmodulin and Ca2+ is an important function of these isoenzymes, which provide fine-tuning mechanisms for calmodulin action.

Development of the early mucosal lesions in experimental inflammatory bowel disease--implications for pathogenesis

The purpose of this study was to better establish the morphologic basis of the early mucosal lesions of experimental inflammatory bowel disease because understanding the development of these lesions has important pathogenetic implications. Sprague-Dawley rats were given 1.5% hydrolyzed lambda-carrageenan orally for 30 days. This produced small intestinal lesions which were then evaluated. Light microscopy showed an increased amount of inflammatory cells in the gut wall with prominent Peyer's patches, microgranulomas, crypt abscesses, pin-point ulcerations, and a repair reaction. Scanning electron microscopy revealed pin-point ulcerations in relation to Peyer's patches. Transmission electron microscopy, in addition to the above findings, showed disruptions of enterocyte microvilli and terminal webs. Follicle-associated epithelium appeared to be a predictive site for the development of crypt abscesses and pin-point ulcerations. Enzyme-linked immunoadsorbent assays indicated that orally administered carrageenan elicited a systemic antibody response. Our results suggest that damage to enterocyte microvilli and terminal webs may be important early events in the morphogenesis of the lesions.

Platelet-activating-factor-induced changes in cardiovascular function and oxyradical status of myocardium in presence of the PAF antagonist CV-6209

The effects of platelet-activating factor (PAF) on cardiac function and contractility and its mechanism of action are not fully understood. The authors investigated the effects of PAF in the absence or presence of a potent PAF antagonist CV-6209 on the cardiac function and contractility; lipid peroxidation product malondialdehyde (MDA), an indirect measure of oxygen free radicals; serum creatine kinase (CK); blood lactate; and pH in anesthetized dogs. CV-6209 (1 mg/kg, IV) did not produce significant changes in the various parameters studied. PAF (1 microgram/kg, IV) produced decreases in the cardiac function (cardiac index, left ventricular work index) and indices of cardiac contractility [(+) and (-) dp/dt, dp/dt at CPIP, (dp/dt)/IP, dp/dt at CPIP/IP, Vmax] and increases in the systemic and pulmonary vascular resistance. It also produced increases in cardiac MDA, serum CK, blood lactate, and H+ and decreases in blood pH and HCO3-. CV-6209 completely prevented the PAF-induced changes in the hemodynamic and biochemical parameters. These results suggest that PAF-induced cardiac depression may be due to PAF-induced release of oxyradicals from neutrophils and that PAF antagonist may be useful in counteracting the deleterious effects of PAF on the cardiovascular system.

A critical review of the neurotoxicity of styrene in humans

Styrene monomer is an aromatic industrial solvent. It is used to make polystyrene, resins, rubber, reinforced material and boats. Humans are exposed to styrene in occupational situations mostly during spraying processes at work, most of which is inhaled. The major neurotoxic effects of styrene as reviewed are prenarcotic effects, electroencephalographic abnormalities, slowing of motor, sensory and distribution nerve conduction velocities that reveal the possibility of polyneuropathy, dysfunction of the autonomic nervous system, slowing of reaction times, and centrally-controlled otoneurotoxicity. In acute exposure situations reversal of adverse effects has been observed; however, the impact of long-term exposure needs further studies. Dopamine depletion has been reported as a neurochemical basis of the neurotoxicity of styrene. Styrene epoxide, a toxic intermediate metabolite, has also been reported to deplete glutathione and cause lipid peroxidation, possibly leading to neuronal membrane damage. Raised concentrations of glial fibrillary acidic protein has been reported as an indicator of neurotoxicity in rats, which may damage the brain through astrogliosis phenomenon. This damage is also correlated to the toxic effects of styrene epoxide. Recently decreased monoamine oxidase type B activity in peripheral blood cells has been investigated as biochemical indicator of neurotoxicity of styrene in workers. There is a need for long-term studies, consideration of confounding factors (smoking, alcohol, diet, drugs, working environment and exposure to other solvents), and the effects on different ethnic and racial groups. More electroencephalographic studies and computer tomographic investigations are desired. Further reduction of the exposure limit to below 50 ppm is recommended.

Antioxidant enzymes in hypercholesterolemia and effects of vitamin E in rabbits

We investigated the effects of high cholesterol diet in the absence and presence of vitamin E on the activity of antioxidant enzymes [superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px)] in rabbits. The animals were divided into 4 groups each comprising of 10 rabbits. Group I, regular rabbit chow diet; Group II, regular rabbit chow diet with added vitamin E; Group III, high cholesterol diet; and Group IV, high cholesterol diet+vitamin E. Antioxidant enzymes of blood were measured in each group before and after 1, 2, 3, and 4 months on the experimental diets. The aorta was removed at the end of the protocol for measurement of antioxidant enzymes. There was a decrease in activity of SOD and GSH-Px and an increase in activity of catalase in blood of Group III. Vitamin E produced a decrease in blood SOD, catalase and GSH-Px activity in Group II and prevented the decrease in SOD and GSH-Px activity in Group IV but did not affect the changes in the catalase activity. SOD, catalase and GSH-Px activity of aortae from Group III increased significantly, while catalase activity increased and GSH-Px activity decreased in those from Group II. Vitamin E prevented the cholesterol-induced rise in catalase and GSH-Px activity in aorta but did not prevent the rise in SOD activity. These results suggest that the activity of antioxidant enzymes in blood is affected differently from that in aortic tissue. There appears to be a mutually supportive interaction among the antioxidant enzymes which provide defense against oxidant injury. The protective effects of vitamin E against hypercholesterolemic atherosclerosis may not be due to changes in the antioxidant enzymes but may be mainly mediated through its chain-breaking antioxidant activity.

Ginsenosides are potent and selective inhibitors of some calmodulin-dependent phosphodiesterase isozymes

The effects of various ginsenosides on calmodulin-dependent phosphodiesterase isozymes have been investigated. Ginsenosides were found to be potent inhibitors of bovine heart calmodulin-dependent phosphodiesterase and the 60-kDa isozyme of bovine brain calmodulin-dependent phosphodiesterase but not of the 63-kDa isozyme of bovine brain calmodulin-dependent phosphodiesterase. Since the inhibition of phosphodiesterase by ginsenosides was overcome by increasing the concentration of calmodulin, this suggests that ginsenosides act specifically and reversibly against the action of the calmodulin. These compounds therefore should be valuable tools to investigate the diverse physiological roles of distinct phosphodiesterase isozymes.

Cardiac depressant effects of oxygen free radicals

In many clinical situations, including cardiac ischemia/reperfusion, elective cardiac arrest, and renal dialysis, the chances of increased production of oxygen free radicals (OFR) exist. OFR have been implicated as a causative factor of cell damage in several pathologic conditions. The effects of exogenous OFR, generated by xanthine plus xanthine oxidase, in the absence and in the presence of OFR scavenger (superoxide dismutase [SOD]) on the contractility of isolated perfused heart of rabbit were studied. OFR produced concentration-dependent decreases in the contractility of perfused heart. SOD prevented the OFR-induced decreases in the left ventricular contractility. Xanthine produced an increase in the contractility of isolated perfused rabbit's heart. Xanthine oxidase produced a marked decrease in the left ventricular contractility. Repeated administration of xanthine oxidase produced accelerated and greater decreases in the contractility of perfused heart when compared with that of the initial administration of the drug. Effects of xanthine or xanthine oxidase on the cardiac function and contractility were also studied in anesthetized dogs. Xanthine alone had no significant effect on the cardiac function and indices of myocardial contractility. However, xanthine oxidase produced a marked decrease in the mean aortic pressure, left ventricular work index, heart rate, cardiac index, left ventricular systolic pressure, left ventricular end-diastolic pressure, (+) and (-) dp/dt of left ventricular pressure, and other indices of myocardial contractility [(dp/dt)/PAW (pulmonary arterial wedge pressure)]; and an increase in the total systemic and pulmonary vascular resistance. Repeated administration of xanthine oxidase in anesthetized dogs had lesser effects on the cardiovascular system when compared with those from the initial dose of the drug. These results suggest that OFR are cardiac depressant. Clinical situations wherein there is an increased production of OFR or increased formation of xanthine and xanthine oxidase may be associated with decreased cardiac function and contractility. Scavengers of OFR may protect the heart from the deleterious effects of OFR in such clinical conditions.

Oxygen free radicals and hypercholesterolemic atherosclerosis: effect of vitamin E

We investigated the effects of a high-cholesterol diet in the presence and absence of vitamin E on the lipid peroxidation product malondialdehyde of blood and aortic tissue, the oxygen-free-radical-producing activity of polymorphonuclear leukocytes (PMNs) (PMN chemiluminescence), and the blood lipid profile in rabbits. The animals were divided into four groups each of which comprised 10 rabbits. Rabbits in group I received a regular rabbit chow diet; those in group II received vitamin E; those in group III received high cholesterol + vitamin E; and those in group IV received a high-cholesterol diet. Blood concentrations of triglycerides, total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), very low-density lipoprotein cholesterol (VLDL-C), malondialdehyde, and PMN chemiluminescence were measured. The aorta of each rabbit was removed at the end of the protocol for assessment of atherosclerotic changes (gross and microscopic) and malondialdehyde. Serum triglycerides, total cholesterol, HDL-C, LDL-C, and VLDL-C increased while HDL/LDL ratio decreased in groups III and IV but remained unchanged in group I. There was an increase in the HDL-C component and HDL/LDL ratio and a decrease in the LDL-C component and triglycerides in group II. Blood and aortic tissue malondialdehyde increased in group IV but decreased in groups II and III. PMN chemiluminescence increased in groups III and IV. Atherosclerotic changes were marked in group IV as compared with those in group III. However, histologic changes in the aortas were similar in groups III and IV. The increased levels of blood and aortic tissue malondialdehyde and PMN chemiluminescence, which were associated with development of atherosclerosis, suggest a role of oxygen free radicals in the pathogenesis of hypercholesterolemia-induced atherosclerosis. The protection afforded by vitamin E, which was associated with a decrease in blood and aortic tissue malondialdehyde concentration in spite of hypercholesterolemia, supports the hypothesis that oxygen free radicals are involved in the development of hypercholesterolemic atherosclerosis.

Construction and characterization of a high-affinity chimeric anti-colorectal carcinoma antibody ccM4

We have produced a high-affinity chimeric anti-colorectal carcinoma antibody, ccM4, chimerized in both heavy and light chains by the construction of two expression vectors, the chimeric heavy-chain expression vector mpSV2neo-EP1-Vm4Cr1 and chimeric light-chain vector mpSV2gpt-EP1-VKCK. These vectors contained the neo or gpt gene as a selection marker, the murine immunoglobulin promoter and enhancer (EP1), the genomic DNA fragments of human immunoglobulin constant region (CK and C gamma 1), and murine cDNA fragments of VH and VK region amplified and cloned directly from the B72.3 hybridoma RNA by the polymer chain reaction technique. These two vector DNAs were sequentially transfected into the SP2/0Ag14 cell line. Transfectants were selected in media containing both G418 and mycophenolic acid. The ccM4 antibody was purified from transfectant supernatants with positive binding reactivity for the TAG72 antigen on a protein A column. We demonstrated that ccM4 antibody retained the same high binding reactivity for the TAG72 antigen as its counterpart, the high-affinity chimeric heavy-chain cB72.3m4 antibody. The ccM4 antibody bound specifically to human colon cancer cells, displayed biodistribution patterns similar to cB72.3m4 antibody, and mediated effective antibody-dependent cellular cytotoxicity to human OVCAR3 tumor cells. Therefore, the high-affinity chimeric ccM4 antibody should be useful in cancer immunotherapy.

During repetitive forebrain ischemia, post-ischemic hypothermia protects neurons from damage

In rodents damage from repetitive transient cerebral ischemia is more severe than that seen with a single ischemic insult of similar duration. Mild hypothermia has been shown to be very effective in protecting the brain during single ischemic insults. We tested the protective effects of hypothermia in repetitive ischemic insults. We used the gerbil model of repetitive ischemia (three minutes ischemia repeated at one hourly intervals three times) and histological evaluation was done using the silver staining technique. Our study reveals that a decrease in body and scalp temperature by 1-2 degrees Celsius can significantly reduce neuronal damage in the cerebral cortex, CA1 region of the hippocampus and substantia nigra reticulata during repetitive ischemia. As the hypothermia was induced after the initial insult, we believe this offers an opportunity for intervention in the clinical settings.

Detection of ischemia-reperfusion cardiac injury by cardiac muscle chemiluminescence

Various methods have been used in the past to assess the implication of oxygen free radicals (OFR) in ischemia-reperfusion-induced cardiac injury. Luminol-enhanced tert-butyl-initiated chemiluminescence in cardiac tissue reflects oxidative stress and is a very sensitive method. It was used to elucidate the role of OFR in cardiac injury due to ischemia and reperfusion. Studies were conducted on perfused isolated rabbit hearts in three groups (n = 8 in each): I, control; II, submitted to global ischemia for 30 min; III, submitted to ischemia for 30 min followed by reperfusion for 60 min. The heart tissue was then assayed for chemiluminescence (CL); content of malondialdehyde (MDA), an indicator of OFR-induced cardiac injury; and activity of tissue levels of antioxidants [superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px)]. The control values for left and right ventricular CL and malondialdehyde were 81.1 +/- 15.4 (S.E.) and 182.4 +/- 50.3 (S.E.), mv.min.mg protein-1; and 0.024 +/- 0.006 (S.E.) and 0.324 +/- 0.005 (S.E.) nmoles.mg protein-1 respectively. Ischemia produced an increase in the cardiac CL (3.3 to 4.4 fold) and MDA content (2 to 2.6 fold). Reperfusion following ischemia also produced similar changes in CL and MDA content. The control values for activity of left ventricular SOD, catalase, and GSH-Px were 45.77 +/- 1.73 (S.E.) U.mg protein-1, 5.35 +/- 0.51 (S.E.) K.10(-3).sec-1.mg protein-1, and 77.50 +/- 7.70 (S.E.) nmoles NADPH.min-1.mg protein-1 respectively. Activities of SOD and catalase decreased during ischemia but were similar to control values in ischemic-reperfused hearts. The GSH-Px activity of left ventricle was unaffected by ischemia, and ischemia-reperfusion. GSH-Px activity of the right ventricle increased with ischemia, and ischemic-reperfusion. These results indicate that cardiac tissue chemiluminescence would be a useful and sensitive tool for the detection of oxygen free radical-induced cardiac injury.