Cardioplegic arrest with L-arginine improves myocardial protection: results of a prospective randomized clinical trial

Caveolin as a potential drug target for cardiovascular protection

Caveolae and caveolin are key players in a number of disease processes. Current research indicates that caveolins play a significant role in cardiovascular disease and dysfunction. The far-reaching roles of caveolins in disease and dysfunction make them particularly notable therapeutic targets. In particular, caveolin-1 (Cav-1) and caveolin-3 (Cav-3) have been identified as potential regulators of vascular dysfunction and heart disease and might even confer cardiac protection in certain settings. Such a central role in vascular health therefore makes manipulation of Cav-1/3 function or expression levels clear therapeutic targets in a variety of cardiovascular related disease states. Here, we highlight the role of Cav-1 and Cav-3 in cardiovascular health and explore the potential of Cav-1 and Cav-3 derived experimental therapeutics.

L-arginine cardioplegia reduces oxidative stress and preserves diastolic function in patients with low ejection fraction undergoing coronary artery surgery

PL-arginine cardioplegia decreases biochemical markers of myocardial damage and oxidative stress in patients with normal left ventricular function. We investigated the effects of L-arginine supplemented cardioplegic arrest in patients with reduced ejection fraction. Fifty-three adult patients with left ventricular ejection fraction <35% undergoing elective coronary artery bypass surgery were randomised to receive blood cardioplegia with or without L-arginine. Following cardiopulmonary bypass, measured endpoints were cardiac troponin-I concentration at 12 and 24 hours, coronary sinus concentrations of malondialdehyde and superoxide dismutase activity at five and 15 minutes, lactic acid flux at one, five and 15 minutes and left ventricular systolic and diastolic function after protamine administration. There were no differences in cardiac troponin-I between groups. Malondialdehyde was lower in the L-arginine group, 0.28 ± 0.12 vs 0.48 ± 0.32 (5 minutes) and 0.31 ± 0.14 vs 0.38 ± 0.15 nmol.ml(-1) (15 minutes) (P=0.0004). Superoxide dismutase activity was higher in L-arginine group, 229 ± 87 vs 191.3 ± 68 (5 minutes), 229 ± 54 vs 198 ± 15 nmol.minute(-1).m(l) (15 minutes) (P=0.005). Lactic acid flux was lower in L-arginine group, 0.15 ± 0.23 vs 0.48 ± 0.32 (1 minute), 0.08 ± 0.19 vs 0.38 ± 0.31 (5 minutes) and -0.15 ± 0.13 vs 0.26 ± 0.30 mmol.l(-1) (15 minutes), (P=0.0003). There was no difference in left ventricular systolic function. The mitral annular tissue Doppler inflow (e') velocity during early diastole improved in the L-arginine group following cardiopulmonary bypass (control 4.2 ± 1.9 cm.s(-1) to 3.6 ± 1.2 cm.s(-1) vs L-arginine 3.8 ±1.2 cm.s(-1) to 4.6 ± 1.4 cm.s(-1)) (P=0.018). In patients with reduced ejection fraction, L-arginine supplemented cardioplegic arrest did not affect postoperative cardiac troponin-I levels, but attenuated cardiac cellular peroxidation and improved early left ventricular diastolic function.

Protective effect of L-arginine in experimentally induced myocardial ischemia: comparison with aspirin

OBJECTIVE

Coronary artery diseases including myocardial ischemia (MI) remain one of the leading causes of death worldwide. This study was designed to compare the protective effect of L-arginine versus aspirin from the biochemical changes associated with MI injury.

EXPERIMENTAL DESIGN

Four groups of male New Zealand white rabbits were investigated. Normal group (n = 8) rabbits were fed standard chow pellets, untreated MI group (n = 16), where hypercholesterolemia was induced by feeding the animals with a diet containing 2% cholesterol for 28 days, L-arginine group (n = 12) rabbits were fed a 2% cholesterol-enriched diet in conjunction with L-arginine (2.25 g %) in drinking water for 28 days, and aspirin group (n = 12) rabbits were fed 2% cholesterol-enriched diet in conjunction with aspirin administered orally (0.7 mg/kg per d) for 28 days. After 28 days, MI was induced in all groups, except the normal group, by a single subcutaneous (sc) injection of isoproterenol hydrochloride (0.2 mg/kg body weight [bw]). Animals were sacrificed 6 hours later.

RESULTS

Our results showed that L-arginine was more effective than aspirin in reducing platelet aggregation, reducing low-density lipoprotein (LDL) oxidizability, preventing aortic intimal thickening, and maintaining histological architecture of the myocardium. Both drugs, however, had similar positive effects on plasma fibrinogen levels and on the prevention of myocardial release of cardiac troponin I and creatine kinase-MB. The effect on hypercholesterolemia was insignificant for both drugs. Aspirin was more effective than L-arginine in prolonging prothrombin time.

CONCLUSION

L-arginine supplementation represents a potentially novel nutritional strategy for preventing and treating coronary artery diseases especially in cases of aspirin resistance and/or hypersensitivity.

The right ventricle in cardiac surgery, a perioperative perspective: II. Pathophysiology, clinical importance, and management

The importance of right ventricular (RV) function in cardiovascular disease and cardiac surgery has been recognized for several years. RV dysfunction has been shown to be a significant prognostic factor in cardiac surgery and heart transplantation. In the first article of this review, key features of RV anatomy, physiology, and assessment were presented. In this second part, we review the pathophysiology, clinical importance, and management of RV failure in cardiac surgery.

Effect of myocardial protection and perfusion temperature on production of cytokines and nitric oxide during cardiopulmonary bypass

PURPOSE

To investigate the effects of different conditions used during cardiopulmonary bypass (CPB) surgery on accompanying production of cytokine and nitric oxide (NO).

METHODS

Patients undergoing CPB for the first time were prospectively enrolled and divided into two groups according to CPB parameters performed: i) normothermia (36.5-37 degrees C) with blood cardioplegia (NB group, n=10) and ii) hypothermia (29-31 degrees C) with crystalloid cardioplegia (HC group, n=10). Plasma samples obtained following intubation (baseline), during (5 and 30 min) and after (4 and 24 h) CPB were assayed for cytokines (ELISA) and NO metabolites (Griess reaction).

RESULTS

Peak concentrations of interleukin (IL)-6 and IL-8 were reached at 4 h post CPB in both groups, but in the HC group those levels increased earlier and persisted for longer (24 h) compared to baseline (P < 0.05). IL-10 levels also increased at 4 h compared to baseline, but only significantly so in the HC group. NO metabolites were reduced in HC group at all time points compared to baseline (P < 0.05), while no significant differences were detected in the NB group.

CONCLUSION

The association between increased systemic levels of cytokines and reduced NO production in the HC group suggests that different myocardial protection and/or perfusion temperature used during CPB may contribute to the extent of inflammatory response.

Oxidative stress and atrial fibrillation after cardiac surgery: a case-control study

BACKGROUND

New-onset postoperative atrial fibrillation (PAF) continues to be among the most common complications after cardiac surgery, leading to significant morbidity and cost. We studied the role of oxidative stress on patients after cardiopulmonary bypass.

METHODS

Patients undergoing coronary artery bypass grafting or valve procedures who exhibited new-onset PAF (n = 11) and those who remained in sinus rhythm (n = 13) were prospectively matched based on preoperative, intraoperative, and postoperative characteristics. Postoperative atrial fibrillation was assessed by electrocardiogram and must have required initiation of antiarrhythmic therapy or anticoagulation. Right atrial and skeletal muscle samples were harvested before and after cardiopulmonary bypass for oxidative protein immunostaining (Oxyblot assay). Serum samples were collected preoperatively and postoperatively at 6 hours and day 4 for microarray assessment of gene expression and to quantify total peroxide levels.

RESULTS

Patients with PAF had significantly more elevation in total peroxide levels in serum compared with patients in sinus rhythm at 6 hours (5.83 +/- 1.9 versus 2.02 +/- 0.2 fold, respectively; p = 0.039) but not at day 4 (3.81 +/- 1.2 versus 2.17 +/- 0.5 fold, respectively; p = 0.188). Patients with PAF also had significantly more myocardial oxidation compared with patients in sinus rhythm at 6 hours (4.19 +/- 1.4 versus 0.94 +/- 0.3 fold, respectively; p = 0.021). Increased serum peroxide levels in patients who exhibited PAF correlated with elevated myocardial protein oxidation but not peripheral muscle oxidation. Gene expression analysis revealed a differential genomic response in patients with new-onset PAF (more oxidation) compared with patients in sinus rhythm (more reduction).

CONCLUSIONS

Patients who exhibit PAF after cardiac surgery have significantly increased acute oxidative stress, which translates into increased myocardial oxidation. Also, patients with PAF have a differential oxidative genomic response after cardiopulmonary bypass that may predispose them to oxidative stress.

Limitation of myocardial and endothelial injury of the rat heart graft after preservation with Centre de Résonance Magnétique Biologique et Médicale (CRMB) solution

Myocardial injury caused by prolonged storage compromises post-transplantation contractile performance and induces endothelial injury. The aim of this study was to compare a solution developed in our laboratory [Centre de Résonance Magnétique Biologique et Médicale (CRMBM) solution] with a widely used solution (Celsior, Genzyme, Saint Germain en Laye, France). Metabolic and contractile parameters as well as indexes of endothelial injury were measured in a heterotopic rat heart transplantation model with a 3-h ischaemia and a 1-h reperfusion. The two solutions were randomly used for cardioplegia and graft preservation in six experiments each. During reperfusion, developed pressure and rate pressure product were higher with CRMBM compared with Celsior (P = 0.0002 and P = 0.0135, respectively). Phosphocreatine and adenosine triphosphate (ATP) concentrations after reperfusion were significantly higher with CRMBM (P = 0.0069 and P = 0.0053, respectively). Endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS) protein expression were decreased to the same extent after reperfusion compared with baseline with CRMBM (P = 0.0001 and P < 0.0001, respectively) and Celsior (P = 0.0007 and P < 0.0001, respectively). Total nitrate concentration (NOx) was significantly increased after reperfusion with CRMBM (P < 0.0001 versus baseline and P < 0.0001 versus Celsior). Na,K-ATPase activity was decreased in both groups versus baseline after reperfusion (P < 0.0001 for CRMBM and P < 0.0001 for Celsior). We showed limitation of both myocardial and endothelial damage with CRMBM compared with Celsior during heterotopic rat heart transplantation in vivo.

Nitric oxide homeostasis as a target for drug additives to cardioplegia

The vascular endothelium of the coronary arteries has been identified as the important organ that locally regulates coronary perfusion and cardiac function by paracrine secretion of nitric oxide (NO) and vasoactive peptides. NO is constitutively produced in endothelial cells by endothelial nitric oxide synthase (eNOS). NO derived from this enzyme exerts important biological functions including vasodilatation, scavenging of superoxide and inhibition of platelet aggregation. Routine cardiac surgery or cardiologic interventions lead to a serious temporary or persistent disturbance in NO homeostasis. The clinical consequences are "endothelial dysfunction", leading to "myocardial dysfunction": no- or low-reflow phenomenon and temporary reduction of myocardial pump function. Uncoupling of eNOS (one electron transfer to molecular oxygen, the second substrate of eNOS) during ischemia-reperfusion due to diminished availability of L-arginine and/or tetrahydrobiopterin is even discussed as one major source of superoxide formation. Therefore maintenance of normal NO homeostasis seems to be an important factor protecting from ischemia/reperfusion (I/R) injury. Both, the clinical situations of cardioplegic arrest as well as hypothermic cardioplegic storage are followed by reperfusion. However, the presently used cardioplegic solutions to arrest and/or store the heart, thereby reducing myocardial oxygen consumption and metabolism, are designed to preserve myocytes mainly and not endothelial cells. This review will focus on possible drug additives to cardioplegia, which may help to maintain normal NO homeostasis after I/R.

Effect of intravenous N-acetylcysteine on outcomes after coronary artery bypass surgery: A randomized, double-blind, placebo-controlled clinical trial

OBJECTIVE

N-acetylcysteine, a potent anti-inflammatory and antioxidant agent, is known to decrease the production of reactive oxygen species after cardiac surgery. The objective of this study was to evaluate the effects of intravenous N-acetylcysteine on clinical and biochemical outcomes after coronary artery bypass surgery with cardiopulmonary bypass.

METHODS

One hundred patients (mean age 60.5 years, range 43-78 years, 89% male) undergoing coronary artery bypass grafting at the Montreal Heart Institute were randomized to receive either N-acetylcysteine (600 mg orally the day before and the morning of the operation, a bolus of 150 mg/kg of intravenous N-acetylcysteine before skin incision, followed by perfusion at 12.5 mg x kg(-1) x h(-1) over 24 hours; n = 50) or placebo (n = 50). The patients and clinical team were blinded to group assignments. Preoperative characteristics were similar between the two groups. Postoperative clinical data (death, myocardial infarction, low-output syndromes, arrhythmias, bleeding, transfusion requirements, and intensive care unit and hospital lengths of stay) and biochemical markers (creatine kinase MB, troponin T, creatinine, hemoglobin, and platelet levels) were evaluated serially over 4 days.

RESULTS

Clinical outcomes were not significantly different between the two groups with regard to the incidence of death, myocardial infarction, bleeding, transfusion requirements, intubation time, and hospital length of stay. No differences were found in postoperative biochemical markers (troponin T, creatine kinase MB, creatinine, hemoglobin, and platelets) between the groups. No differences were observed between the groups in interleukin-6 production (P = not significant).

CONCLUSIONS

Prophylactic use of N-acetylcysteine in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass does not lead to improvement in clinical results or biochemical markers. Further strategies to decrease reperfusion injury should be devised.

Reduced cytokines release and myocardial damage in coronary artery bypass patients due to L-arginine cardioplegia supplementation

BACKGROUND

Recently, L-arginine has been added to cardioplegia to limit myocardial ischemic damage. The mechanism of action is related to the production of nitric oxide, with vasodilatation and reduction of endothelial dysfunction. Our prospective randomized study on coronary artery bypass patients investigates the effect of L-arginine on myocardial stress as expressed by myocardial cytokines release and myocardial ischemia in terms of troponin T concentration.

METHODS

Coronary artery surgery patients were randomly assigned to receive 7.5 g L-arginine in 500 mL of cardioplegic solution (group A). Group B was used as control. Cold blood 4:1 anterograde and retrograde cardioplegia with warm induction was administered. Blood samples were collected from the retrograde coronary sinus catheter to determine interleukin-2 receptor, interleukin-6, and tumor necrosis factor levels. Serum samples at different time points were also analyzed to measure myocardial ischemia markers. Hemodynamic and echocardiographic evaluations were obtained perioperatively.

RESULTS

Sixty-five patients were enrolled (group A, treated with L-arginine, n = 33; group B, control, n = 32). Wedge pressure and intensive care unit stay were significantly reduced in group A (p = 0.023 and p = 0.03, respectively). Cytokines levels were lower in group A, with a significance for interleukin-6 (p = 0.026); troponin T was reduced in treated patients (0.33 versus 0.57 ng/mL at 18 hours: p = 0.009).

CONCLUSIONS

Coronary artery surgery patients benefit from L-arginine cardioplegia supplementation in terms of reduced inflammatory reaction, limitation of myocardial ischemia, and better hemodynamic performance. Moreover, a clinical advantage is evident in terms of a shorter intensive care unit stay in patients treated with L-arginine.

S-nitroso human serum albumin attenuates ischemia/reperfusion injury after cardioplegic arrest in isolated rabbit hearts

BACKGROUND

Depletion of nitric oxide (NO) is associated with ischemia/reperfusion injury. The novel NO donor, S-nitroso human serum albumin (S-NO-HSA), could bridge NO depletion during reperfusion in cardiac transplantation and minimize ischemia/reperfusion injury.

METHODS

In an isolated erythrocyte-perfused working heart model, rabbit hearts were randomly assigned after assessment of hemodynamic baseline values to receive S-NO-HSA (0.2 micromol/100 ml, n = 8), L-arginine (10 mmol/100 ml, n = 8) or albumin (control) (0.2 micromol/100 ml, n = 8). After 20 minutes of infusion, the hearts were arrested and stored in Celsior (4 degrees C) enriched with respective drugs for 6 hours, followed by 75 minutes of reperfusion. Hemodynamic values were assessed and biopsy specimens were taken to determine calcium-ionophore stimulated release of NO and superoxide.

RESULTS

During early reperfusion, recovery of cardiac output (75% +/- 6% vs 49% +/- 5%, p < 0.05) and coronary flow (99% +/- 8% vs 70% +/- 5%, p < 0.05) were higher, and myocardial oxygen consumption was reduced in the S-NO-HSA Group compared with Control (4.08 +/- 0.46 ml/min/0.1 kg vs 6.78 +/- 0.38 ml/min/0.1 kg, p < 0.01). At the end of the experiment cardiac output (53% +/- 5% vs 27% +/- 5%, p < 0.01) was higher and left atrial pressure (115% +/- 9% vs 150% +/- 8%, p < 0.05) was lower in the S-NO-HSA Group compared with Control. NO release was increased (1,040 +/- 50 nmol/liter and 1,070 +/- 60 nmol/liter vs 860 +/- 10 nmol/liter, p < 0.01) and superoxide release diminished (31 +/- 5 nmol/liter and 38 +/- 5 nmol/liter vs 64 +/- 5 nmol/liter, p < .01) in the S-NO-HSA and L-arginine Groups compared with Control.

CONCLUSION

S-NO-HSA improved hemodynamic functions after prolonged hypothermic cardiac arrest by supplementing NO and thereby decreasing ischemia/reperfusion injury.

Blood Cardioplegia Provides Superior Protection in Infant Cardiac Surgery

BACKGROUND

We hypothesized that blood cardioplegia preserves myocardial metabolism and function more effectively than St Thomas' crystalloid cardioplegia in infant cardiac surgery.

METHODS

Thirty infants with atrioventricular septal defects were randomly allocated to either blood or crystalloid intermittent cold (4 degrees C) cardioplegia. Arterial and coronary sinus blood was analyzed for lactate and oxygen. Cardiac output (thermodilution) and left ventricular function (echocardiography) were evaluated.

RESULTS

The lactate concentration in coronary sinus blood early after bypass was significantly higher after crystalloid cardioplegia than after blood cardioplegia (2.1 +/- 0.3 vs 1.3 +/- 0.1 mmol/L, p = 0.006), with a significant myocardial release of lactate after crystalloid but not after blood cardioplegia. Oxygen extraction (arterial-coronary sinus O2 content) was higher early after crystalloid cardioplegia (3.02 +/- 0.13 vs 2.35 +/- 0.22 mmol/L, p = 0.01), possibly reflecting a difference in oxygen debt. The cardiac index was higher after blood cardioplegia (4.9 +/- 0.3 vs 4.0 +/- 0.3 L/min(-1)/m(-2), p = 0.04) and echocardiographic grading of left ventricular function was better (4.1 +/- 0.17 vs 3.5 +/- 0.22 arbitrary units, p = 0.046).

CONCLUSIONS

This study indicates that blood cardioplegia preserves myocardial metabolism and function more effectively than crystalloid cardioplegia in infant cardiac surgery. The clinical significance of this finding is uncertain, but the more than 20% increase in cardiac index in the critical phase during weaning from bypass may be advantageous.

Efficiency of L-arginine enriched cardioplegia and non-cardioplegic reperfusion in ischemic hearts

OBJECTIVE

Endothelial dysfunction with decreased nitric oxide (NO) levels has been implicated on reperfusion injury. Although L-arginine has been shown to diminish reperfusion injury in in vitro studies, clinical studies were very limited.

METHODS

Forty patients with acute myocardial ischemia undergoing CABG were randomized to a study and a control group. L-Arginine was added to cardioplegia solutions in study group. A non-cardioplegic warm blood solution with 8 mmol/l L-arginine infused for controlled reperfusion. Control patients received same protocol without L-arginine. Myocardial O2, lactate, nitrite and malondialdehyde extractions were measured in addition to calculation of CK-MB/CPK ratio and hemodynamic data.

RESULTS

While there was no mortality in study group, one patient in control group died. Overall and nitrite (P=0.01) and lactate extractions (P=0.04) was higher in study and control groups, respectively. Myocardial O2 uptake was higher and malondialdehyde extraction was lower in study group. CK-MB/CPK ratio at postoperative sixth hour was also significantly lower in study group. Ninety percent of the study group had spontaneous return of the sinus rhythm, while 80% of the control patients required defibrillation (P<0.0001). In addition to significantly better hemodynamics, perioperative myocardial infarction incidence was lower (P=0.037), the length of intensive care unit (P=0.009) and hospital (0.014) stays were shorter in study group.

CONCLUSIONS

Use of L-arginine for protection of acutely ischemic myocardium appears to be a safe technique. L-Arginine supplementation increased NO levels and attenuated free O2 radical mediated myocardial injury. Controlled reperfusion with l-arginine enriched non-cardioplegic blood could be a new therapeutic entity to diminish ischemia/reperfusion injury.

Cold blood cardioplegia versus cold crystalloid cardioplegia: A prospective randomized study of 1440 patients undergoing coronary artery bypass grafting

OBJECTIVES

A large number of experimental studies have indicated that blood cardioplegia might be superior to crystalloid cardioplegia for myocardial protection during ischemic arrest. However, no prospectively randomized studies of large patient series have been undertaken to prove potential differences in clinical course.

METHODS

Over a 52-month period, all patients undergoing on-pump coronary artery bypass operated on by 2 surgeons were prospectively randomized to receive either cold crystalloid cardioplegia (group C) or cold blood cardioplegia (group B) during aortic crossclamping.

RESULTS

Altogether, 1440 patients aged 37 to 89 years (median, 66 years) entered the study (group C, n = 719; group B, n = 721). The groups were comparable in all major demographic, preoperative, and operative variables. The clinical course turned out to be nearly identical for both groups. No statistically significant differences were seen concerning spontaneous sinus rhythm after aortic declamping, use of inotropic drugs or intra-aortic balloon pumping, postoperative ventilatory support, bleeding and rate of allogeneic blood transfusions, perioperative myocardial infarction, episodes of atrial fibrillation, stroke or minor neurologic dysfunction, renal function, infections, physical rehabilitation, or mortality. Also, in subgroups of patients at higher operative risk (female sex, age >70 years, unstable angina, diabetes, emergency operation, ejection fraction <0.50, crossclamping time >50 minutes, and EuroSCORE >4), no statistically significant differences could be demonstrated between the groups.

CONCLUSIONS

There were no significant differences whether myocardial protection was performed with cold blood cardioplegia or cold crystalloid cardioplegia during aortic crossclamping in patients undergoing coronary artery bypass grafting. The extra costs related to blood cardioplegia might be saved.

Myocardial Protection after Systemic Application of L-Arginine during Reperfusion

The L-arginine-nitric oxide (NO) pathway plays an important role in ischemia-reperfusion injury. In the present study we investigated the role of NO-precursor L-arginine on cardiac and pulmonary function after reversible hypothermic ischemia. Twelve anesthetized dogs underwent cardiopulmonary bypass. After 60 minutes of hypothermic cardiac arrest, reperfusion was started with application of either saline vehicle (control, n = 6) or L-arginine (40 mg/kg i.v. bolus then 3 mg/kg i.v. infusion during the first 20 minutes of reperfusion, n = 6). The vasodilative response to acetylcholine was significantly higher in the L-arginine group (P < 0.05). The preload recruitable stroke work of the left ventricle decreased significantly after reperfusion, however remained unchanged in the L-arginine group. Arterial blood gas analysis did not show any difference between the two groups. Plasma L-arginine concentration reached peak level at 20 minutes of administration (675.0 +/- 66.6 versus 207.7 +/- 14.5 in the L-arginine group, P < 0.05) and returned to baseline at 40 minutes, while in the control group remained unchanged during ischemia and reperfusion (276.2 +/- 71.6 versus 283.8 +/- 38.5, P < 0.05). Plasma nitrite concentration followed L-arginine changes parallel, however nitrate levels increased slower. Supplementation with L-arginine during reperfusion prevents myocardial and endothelial dysfunction, however does not have any overriding effect on pulmonary function. Considerably rapid elimination of plasma L-arginine was demonstrated during early reperfusion.

Evaluation of nitric oxide release in the coronary effluent by a novel EPR technique: A study on isolated rat hearts subjected to cold cardioplegia and reperfusion

Aim of this study was to investigate the cardiac release of nitric oxide (NO) before and after cold cardioplegia by a novel electron paramagnetic resonance (EPR) technique. Isolated rat hearts were perfused for 20 min in a Langendorff apparatus and then subjected to 3 hours potassium-hypotermic cardioplegia, followed by 20 min reperfusion. The coronary effluent was collected in a flask containing ferrous-bis-diethyldithiocarbamate as a spin trap of NO. Since the trapping agent was not delivered to the heart with the perfusion medium, we avoided that an abnormal extraction of NO from the tissue could inhibit its biological activity. The EPR signal was well detectable after equilibration (25.6 +/- 3.0 nmol/L +/- S.E.M.) and significantly increased following perfusion with 10 micromol/L serotonin (41.1 +/- 3.2 nmol/L) or 10 micromol/L nitroprusside (43.5 +/- 2.9 nmol/L). The basal level of NO did not change after reperfusion, but serotonin administration was not able to stimulate its release. Serotonin failure to stimulate NO production was not due to a loss of endothelial NO synthase, since its protein expression was not modified after reperfusion. The perfusion pressure increased by 51% after reperfusion and was quite completely restored following serotonin or nitroprusside treatment, with respect to the non-stimulated equilibration condition. Therefore, we suggest that the coronary spasm following a cold cardioplegic arrest is not due to an impaired production of basal NO and that NO-donors can be effective in relaxing vascular smooth muscle cells.