Urinary angiotensinogen level is correlated with proteinuria in renal transplant recipients.

Objective: Along with immunologic mechanisms, intrarenal renin-angiotensin system (RAS) activation has been suggested to play a role in the development and progression of chronic allograft injury. In various glomerular diseases, urinary angiotensinogen (AGT) level is a good indicator for the activation of intrarenal RAS. In this study, we aimed to investigate the parameters associated with urinary AGT level in patients with kidney transplantation.

Methods: Seventy renal transplant patients with stable graft function (≥ 6 months after transplantation, serum creatinine level <2 mg/dL) and 21 healthy volunteers were included in the study. Patients were taking standard triple immunosuppressive treatment. Demographic characteristics of patients and healthy volunteers, drug use, and 24-hour ambulatory blood pressure measurements were recorded. Morning second urine and fasting blood samples were taken from all participants. Serum biochemical markers and urine Na, K, uric acid, creatinine, and protein levels were measured. Urinary AGT levels were determined by enzyme-linked immunosorbent assay.

Results: Mean systolic and diastolic blood pressures in patients with renal transplantation were higher than in healthy volunteers. Both urinary AGT-urinary creatinine ratio (UAGT/UCr) and urinary protein-urinary creatinine ratio (UPro/UCr) were higher in kidney transplant patients than in healthy volunteers (P < .01; P < .0001; respectively). In patients with renal transplantation, UAGT/UCr was positively correlated with UPro/UCr and negatively correlated with estimated glomerular filtration rate (eGFR) (r = 0.738; P = .01; and r = -0.397; P = .01; respectively). There was no correlation between UAGT/UCr and other study parameters, including bood pressure levels.

Conclusions: Our findings indicate that high urinary excretion of AGT is associated with proteinuria and lower eGFR in kidney transplant recipients without overt chronic allograft injury. These preliminary results encourage us to design a long-term longitudinal analysis using urinary AGT along with multiple markers to obtain early diagnosis and to predict the prognosis of chronic allograft dysfunction.