Relationship between 24-hour urine sodium level and urine angiotensinogen level in renal transplant patients with proteinuria

Background and aim: Intrarenal local renin angiotensin system (RAS) activation plays an important role in primary hypertension, proteinuria and progress of chronic kidney disease. Hypertension which is seen in renal transplant recipients is an important risk factor for the development of proteinuria and graft failure. It was demonstrated that urinary angiotensinogen (AGT) level reflects intrarenal RAS status in patients with hypertension, proteinuria or chronic kidney disease. The relationship between local RAS activation and urinary sodium excretion was already demonsrated in experimental and animal studies before. However, there isn't enough clinical studies about this subject. The aim of this study is to evaluate the urinary AGT level in renal transplant recipients thereby, search the relationship between local intrarenal RAS with hypertension, proteinuria and urinary sodium excretion. Materials and Methods: Eighty renal transplant recipients who have stabıle graft function (at least six months passed after transplantation, creatinin level<2mg/dl) and fourty healthy volunteers have been included of the study. Both in patients and healthy volunteers besides demographic features also BMI's, mean blood pressures were saved. Blood and urine samples were collected from all patients for laboratory analyses. Sodium, creatinin, protein and albumin levels were measured from 24-hour urine test. Organ recipients were seperated two groups as low proteinuria levels (<300 mg/day),(Group 1) and high proteinuria levels (>300 mg/day)(Group 2). Urine samples of every paticipients were kept in -80 0C until AGT measurements were done. Urine AGT levels measured with ELISA method. Differences between two groups were analyzed with 2-sample t test and Mann-Whitney tests. In order to investigate the correlation between urine AGT levels and other parameters spearman correlatıon test was made. Statistics significence was accepted as p<0,05. Findings: Between the demographic features of transplant recipients of Group 1 and transplant recipients of Group 2 there was no significant difference detected in terms of age, sex, BMI, cigarette use rate, original kidney disease, renal treatment before transplantation, types and doses of immunosupressive drugs, types and doses ofantihypertensive drugs (p>0.05). While proportion of urine albumin/creatinin and urıne angiotensynogen/creatinin levels were measured significantly higher in group 2 than group 1 (p<0.01) ;serum 25-(OH) vitamin D3 and urine sodium excretion levels were lower in group 2 than group 1(p<0.01). Conclusions: In conclusion, according to our study in renal transplant recipients who don't have overt chronic allograft nephropathy in explicit level, while urinary AGT levels have positive correlation with proteinuria they have negative correlation with urinary sodium excretion. In the light of this study, in the early diagnosis of chronic allograft nephropathy and prediction of the prognosis, advanced monitoring studies in which the role of urinary AGT and sodium levels will be searched are required along with the other laboratory and clinical parameters. Keywords: Urinary angiotensinogen, renal transplant recipients, hypertension, proteinuria, renin angiotensin system