Increasing evidence suggests that erythrocytes may participate in atherogenesis. We sought to investigate whether the total cholesterol content of erythrocyte membranes (CEM) is significantly different in patients with stable coronary artery disease (CAD) compared to patients with nonsignificant coronary stenosis and determine the correlation between CEM and the severity of coronary stenosis. Methods. The population included 144 patients, undergoing clinically indicated coronary angiography. The severity of coronary stenosis was scored after coronary angiography and patients were divided into two groups; the -stenosis group (CAD patients, ) had a significant stenosis indicated by coronary angiography and the second group, -stenosis (), had nonsignificant coronary stenosis. Lipid parameters were determined by routine laboratory methods. CEM was measured using an enzymatic assay, and protein content was assessed by the modified Lowry method. Results. The mean of CEM levels was higher () in stable CAD patients (137.2？μg/mg of membrane protein) compared with -stenosis patients (110.0？μg/mg of membrane protein). The coronary artery scores were correlated positively with CEM levels (, ). Conclusion. CEM levels are positively associated with the severity of CAD, meaning that CEM might contribute to the development of CAD. 1. Introduction Coronary artery disease (CAD) is closely associated with advanced atherosclerosis, which reflects several deteriorative phenomena that gradually result in narrowing of coronary arteries, terminating in thrombosis and myocardial infarction. CAD is one of the major causes of mortality and morbidity in both developed and developing countries and is believed to have a multifactorial etiology, composed of numerous biological, environmental, behavioral, and sociocultural factors [1–3]. In addition to traditional risk factors, erythrocyte membrane has been regarded as one of the most important contributors to the initiation and progression of atherosclerosis [4–11]. Although apoptotic macrophages are an important source of cholesterol within atherosclerotic plaques, it is unlikely that all of the cholesterol contained in plaques derives from foam cells alone. Most of the cholesterol in foam cell is esterified , whereas the atherosclerotic lipid core has a remarkably high content of free cholesterol . The most compelling evidence was reported by Arbustini et al. , who identified an erythrocyte membrane protein, glycophorin A, in pulmonary plaques from patients with thromboembolic disease. These findings were repeated in
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