Renalase, an enzyme that breaks down catecholamines like adrenaline and noradrenaline in the blood circulation, was discovered in 2005. The human kidney releases this protein into the bloodstream to regulate blood pressure. Heart transplant recipient show a high prevalence of hypertension. The aim of this study was to assess possible correlations between renalase, blood pressure, and kidney function among 130 prevalent heart transplant recipients. To obtain normal ranges we also studied renalase levels in 27 healthy volunteers.Complete blood counts, urea, serum lipids, fasting glucose, and creatinine were measured using standard laboratory methods in the hospital central laboratory. Renalase was assessed using commercially available kits.In heart transplant recipients renalase levels correlated with age (r=0.25; P<.05); time after transplantation (r=0.22; P<.05); serum creatinine (r=0.85; P<.001); estimated glomerular filtration rate (chronic kidney disease-epidemiological study formula; r=0.59; P<.0001; Modification of Diet of Kidney Disease (r=-0.58; P<.001); Cockcroft-Gault (r=-0.59; P<.001); 24-hour creatinine clearance (r=-0.52; P<.001); NT-proBNP (r=0.41; P<.001); erythrocyte count (r=-0.42; P<.001); hemoglobin (r=0.44; P<.001); cystatin C (r=0.82; P<.001); ejection fraction (r=-0.26; P<.01; and New York Heart Association class (r=0.31; P<.001). Multiple regression analysis showed renalase concentration to be predicted in 75% by serum creatinine (beta value, 0.79; P=.0000000; SE 3.00; F statistics 15.96; P<.0000001). Serum renalase was higher among heart transplant recipients than healthy volunteers.Renalase, highly elevated in heart transplant recipients, is predominantly dependent on kidney function, which deteriorates with time after heart transplantation and age. Further studies are needed to establish its putative role in the pathogenesis of hypertension after transplantation and possible novel targeted therapies. However, is seems that among heart transplant recipients renalase was not related to blood pressure.