Abstract 195: Circadian Rhythm of Plasma and Urinary Angiotensinogen in Patients with Chronic Kidney Disease

Abstract

Recent basic and clinical data demonstrated that the intrarenal renin-angiotensin system (RAS) plays an important role in the progression of chronic kidney disease (CKD). The urinary angiotensinogen (AGT) excretion rate could be a novel biomarker for the activity of the RAS in the kidney. We previously reported that the healthy volunteers do not have a circadian rhythm of AGT level in urine (Hypertension. 2011;57:e78) or in plasma (Hypertension. 2012;60:A399). However, the circadian rhythm of AGT level in urine and in plasma in patients with CKD has not been reported yet. Therefore, this study was performed to investigate the circadian rhythm of AGT level in urine and in plasma in patients with CKD. We recruited 6 CKD patients with continuous proteinuria admitted to the Kagawa University Hospital from 06/2011 to 10/2011 for the purpose of diagnostic renal biopsy. Plasma samples were collected at 06:00, 12:00, and 18:00. Urine samples were collected at 06:00, 09:00, 12:00, and 18:00. Plasma renin activities (PRAs), plasma and urinary AGT concentrations, and urinary albumin (Alb) concentration were measured using commercially available kits. The urinary concentrations of AGT and Alb were normalized by the urinary concentration of creatinine (Cr) (UAGT/Cr and UAlb/Cr, respectively). PRA (2.07 +/- 0.77 ng of angiotensin I/mL/hr at 06:00, 2.45 +/- 0.77 at 12:00, and 2.58 +/- 0.76 at 18:00, P = 0.8853) or plasma AGT (19.9 +/- 2.4 μg/mL at 06:00, 24.1 +/- 3.1 at 12:00, and 23.0 +/- 3.9 at 18:00, P = 0.6300) did not show a circadian rhythm. Moreover, UAlb/Cr (511 +/- 319 mg/g Cr at 06:00, 827 +/- 459 at 09:00, 1479 +/- 862 at 12:00, and 1370 +/- 818 at 18:00, P = 0.6964) or UAGT/Cr (54 +/- 22 μg/g Cr at 06:00, 119 +/- 41 at 09:00, 350 +/- 194 at 12:00, and 198 +/- 104 at 18:00, P = 0.3035) did not show a circadian rhythm. In conclusion, in addition to healthy volunteers, patients with CKD do not have a circadian rhythm of AGT level in urine or in plasma.