Endogenous erythropoietin and a single bolus of 40,000 IU of epoetin alpha do not protect the heart from ischaemia-reperfusion injury during extracorporeal circulation for cardiac surgery.

Erythropoietin (EPO) exerts a tissue-protective activity in several non-haematopoietic tissues such as heart, brain, spinal cord and muscle. We evaluated the relationship between pre-operative endogenous EPO blood levels and myocardial damage in patients undergoing cardiopulmonary bypass (CPB). Furthermore, we investigated whether pre-operative administration of a single bolus of 40,000 IU epoetin alpha (EPOalpha) would reduce troponin I or creatine kinase isoenzyme (CK-MB) after on-pump coronary artery bypass graft (CABG) surgery. Sixty-seven patients (45 CABG, 22 valvular surgery) were enrolled. EPO was measured in the pre-surgical period and correlated to post-surgical troponin I and CK-MB peaks. Subsequently, forty patients scheduled for CABG were randomized into two groups, receiving, respectively, a) standard medical and surgical treatment (20 patients) and b) the same treatment plus 40,000 IU of EPOalpha in a single bolus injection in the immediate pre-surgical period (20 patients). In our population, we did not find any correlation between pre-surgical EPO and post-surgical troponin I or CK-MB peaks (p Pearson > 0.05). Furthermore, patients treated with EPOalpha did not show differences compared to the control group in either troponin I (1.7+/-1.8 vs 2.6+/-3.4, p>0.05) or CK-MB (19.6 +/-13.2 vs 17.1+/-12.6, p>0.05) peaks measured in the post-surgical period.

Structure, production and function of erythropoietin: implications for therapeutical use in cardiovascular disease.

Erythropoietin (EPO) is a 30,400 daltons glycoprotein, consisting of 165 amino acids produced mainly in the kidney and in the liver and regulating erythrocyitosis. It primarily acts on erythroid precursor cell at colony-forming units-erythroid stage inhibiting the apoptosis. EPO binds on a specific membrane receptor thereby activating at least three specific intracellular signaling pathways, such as phosphatidylinositol 3-kinase/ protein kinase B, Ras-mitogen-activated protein kinase and some members of the signal transducers and activators of transcription family. In addition to kidney and liver, EPO mRNA has been detected in other tissues; accordingly EPO receptor has been identified in several type of cells and recent reports have suggested new roles for EPO in non-haematopoietic tissues with a robust evidence for neuroprotective and cardioprotective activity. In different animal models, in vitro, in isolated perfused heart and in vivo, recombinant human erythropoietin protects heart from ischemia reperfusion injury and reduces myocardial damage. EPO tissue protective activity can be separated from erythropoietic activity. Molecules owing the first property but not the second one have been described. In patients with acute myocardial infarction serum EPO level correlates inversely with infarct size. Acute coronary syndrome, extracorporeal circulation and percutaneous coronary intervention are potential fields of application for tissue protective EPO activity to reduce myocardial damage, increase cardiac function ad improve outcome.

Dipyridamole echocardiography and 99mTc-MIBI spect dipyridamole scintigraphy for cardiac evaluation prior to peripheral vascular surgery.

Coronary artery disease accounts for most of the early and late mortality and morbidity associated with vascular surgery. Cardiac pre-operative evaluation is mandatory for the assessment of cardiac risk. The aim of this study is to compare dipyridamole scintigraphy with 99mTc-MIBI (MIBI-dipy) and dipyridamole echocardiography (ECHO-dipy) and to evaluate their capability in identifying cardiac risk for strong events such as death, unstable angina or myocardial infarction. METHODS. Sixty consecutive patients (mean age 67 +/- 7) were enrolled. 52 performed ECHO-dipy, 51 MIBI-dipy. 40 patients went to aorto-femoral or aorto-iliac graft replacement and 15 to vascular angioplasty. Five patients did not undergo surgery. RESULTS. Eighteen patients (30%) had stress defects and 9 patients also rest defects with MIBI-dipy. Six patients new asinergic areas at ECHO-dipy. Three pts died in the first year follow-up for a cerebrovascular event, a myocardial infarction and a sudden death respectively. Sensitivity and specificity, positive and negative predictive value were 100%, 69%, 16%, 100% for MIBI-dipy and 66%, 94%, 40%, 98% for ECHO-dipy. CONCLUSIONS. As other authors reported, stress scintigraphy is a pre-operative test showing high sensitivity but with no satisfying specificity. Stress echocardiography, in our population, can produce a good negative predictive value. It is a less expensive and widespread clinical tool useful in the evaluation of preoperative patients. Its positive predictive power is not satisfying but it is shared with all non-invasive pre-operative tests available now.

Characterization of a calmodulin-dependent high-affinity cyclic AMP and cyclic GMP phosphodiesterase from male mouse germ cells.

Two cyclic nucleotide phosphodiesterase activities were separated by ion-exchange chromatography of cytosol from male mouse germ cells. A form eluted at low salt concentration showed high affinity (Km congruent to 2 microM) and low affinity (Km congruent to 20 microM) for cyclic AMP, and high affinity (Km congruent to 3.5 microM) for cyclic GMP. A second form, eluted at high salt concentration, showed high affinity (Km congruent to 5 microM) for cyclic AMP and was similar to a phosphodiesterase activity described in rat germ cells. The present study was performed to characterize the first form, which represents most of the phosphodiesterase activity in mouse germ cells. The enzyme was sensitive to Ca2+ and calmodulin stimulation, which increased its activity 3-4-fold. Calmodulin stimulation depended on direct interaction of the activator with the enzyme, as indicated by the reversible changes in the chromatographic elution pattern in the presence of Ca2+, as well as by the increase in the sedimentation coefficient in the presence of calmodulin. Reciprocal inhibition kinetics between cyclic AMP and cyclic GMP for the calmodulin-dependent form demonstrated a non-competitive inhibition between the two substrates, suggesting the presence of separate catalytic sites. This is in agreement with kinetic parameters and different thermal stabilities of cyclic AMP- and cyclic GMP-hydrolysing activities. Furthermore, the relevant change in s value, depending on the absence or presence of Ca2+ and calmodulin, suggested that the enzyme is composed of subunits, which aggregate in the presence of the activator. A model for catalytic site composition and reciprocal interaction is also proposed.