Urinary Angiotensinogen Levels Research Articles

Reversibility of the Effects of Aliskiren in the Renal Versus Systemic Circulation

Renal hemodynamic effects of inhibitors of the renin-angiotensin system can increase the risk of acute kidney injury under certain conditions. The BP-lowering effects of the renin inhibitor aliskiren are sustained 3-4 weeks after withdrawal. In this study, the reversibility of the renal hemodynamic effects of aliskiren was tested. In this open-label study, renal perfusion was measured by 1.5-T magnetic resonance imaging-arterial spin labeling in 34 subjects with arterial hypertension before aliskiren (pre-aliskiren), after 4 weeks of aliskiren treatment (300 mg), and 4-5 days (∼2.5-3.0× plasma half-life) after withdrawal (post-aliskiren). Aliskiren reduced systolic BP from 152 ± 14 to 139 ± 16 mmHg (P<0.0001), which was sustained post-aliskiren (136 ± 13 mmHg, P=1.00 versus aliskiren). Aliskiren significantly altered renal perfusion (P=0.005), increasing from 272 ± 25 pre-aliskiren to 287 ± 29 ml/min per 100 g during aliskiren (P=0.03). This increase in renal perfusion was completely reversed post-aliskiren (272 ± 26 ml/min per 100 g, P=0.03 versus aliskiren, P=0.63 versus pre-aliskiren). No changes were noted in urinary angiotensinogen levels. Plasma renin activity was reduced by aliskiren, which was sustained post-aliskiren. Angiotensin II and aldosterone were reduced by aliskiren but recovered post-aliskiren to pre-aliskiren levels. After withdrawal of aliskiren, the effects on BP were sustained, whereas increase in renal perfusion was reversed, which was associated with recovery of angiotensin II and aldosterone to pretreatment levels. Renal hemodynamic effects are more readily reversible than systemic effects of aliskiren.

Direct Renin Inhibition in a Rat Model of Chronic Allograft Injury

Blockade of the renin-angiotensin system (RAS) with angiotensin-converting enzyme (ACE) inhibitors or angiotensin II (Ang II) receptor blockers (ARBs) slow the progression of various chronic kidney diseases and chronic allograft dysfunction. RAS inhibition can be achieved also by directly blocking renin upstream from ACE. However, direct renin inhibition can have additional effects since formation of renoprotective Ang II breakdown products such as angiotensin (Ang) (1-7) that are produced by ACE2 are also inhibited. Using a Fischer-to-Lewis renal transplantation model, the effect of the renin inhibitor aliskiren (10 mg/kg/day) was assessed on the development of chronic allograft dysfunction compared with vehicle treatment and Ang II receptor blockers candesartan. Aliskiren had no effect on renal function (proteinuria, creatinine clearance) or on renal morphological changes (glomerulosclerosis collagen deposition, myofibroblast accumulation and macrophage infiltration) compared with the vehicle- and candesartan-treated animals determined 24 weeks after transplantation. On the other hand, atrophy of tubular cells was significantly attenuated. Candesartan reduced both proteinuria and structural injury of the kidney. In aliskiren-treated animals reduced serum Ang II and Ang (1-7) levels were detected, whereas the level of urine angiotensinogen was unchanged. The renin inhibitor aliskiren does not slow the progression of chronic allograft dysfunction. We suggest that the lack of protection might be due to reduced formation of the protective Ang II breakdown products such as Ang (1-7) or due to unchanged intrarenal RAS activity demonstrated by urinary angiotensinogen levels.

Association between urinary angiotensinogen levels and renal and cardiovascular prognoses in patients with type 2 diabetes mellitus

AIMS/INTRODUCTION: Activation of the renin-angiotensin system (RAS) in the kidney plays an important role in renal function. The aim of this study was to investigate whether plasma and urinary angiotensinogen levels were associated with renal and cardiovascular prognosis in type 2 diabetic patients. MATERIALS AND METHODS: We measured plasma and urinary angiotensinogen levels in the observational follow-up cohort of 234 Japanese type 2 diabetic patients (144 with normoalbuminuria, 90 with albuminuria) enrolled between 1998 and 1999 and followed them up until the end of 2008. The associations of these markers with the annual decline in the estimated glomerular filtration rate (eGFR) and incidence of renal and cardiovascular composite endpoints (chronic hemodialysis, myocardial infarction, angina pectoris, stroke and cerebral hemorrhage) were evaluated. RESULTS: At baseline, urinary angiotensinogen levels correlated with urinary albumin-creatinine ratio, urinary β(2)-microglobulin and inversely with eGFR. In contrast, plasma angiotensinogen levels correlated neither with these renal factors nor with urinary angiotensinogen levels. In the follow-up study (median duration: 9 years), urinary angiotensinogen, but not plasma angiotensinogen, correlated inversely with the annual change in eGFR (r = -0.51, P < 0.001).When patients were divided into four subgroups according to albuminuria and urinary angiotensinogen levels, patients with albuminuria and high urinary angiotensinogen levels showed a progressive decline of eGFR and a higher incidence of renal and cardiovascular composite endpoints. CONCLUSIONS: These results suggest that the higher level of urinary angiotensinogen in type 2 diabetic patients with albuminuria is a high risk factor for worsening renal and cardiovascular complications.

Urinary renin, but not angiotensinogen or aldosterone, reflects the renal renin–angiotensin–aldosterone system activity and the efficacy of renin–angiotensin–aldosterone system blockade in the kidney

To study which renin-angiotensin-aldosterone system (RAAS) component best reflects renal RAAS activity. We measured urinary and plasma renin, prorenin, angiotensinogen, aldosterone, albumin and creatinine in 101 diabetic and nondiabetic patients with or without hypertension. Plasma prorenin was elevated in diabetic patients. Urinary prorenin was undetectable. Urinary albumin and renin were higher in diabetic patients. Men had higher plasma renin/prorenin levels, and lower plasma angiotensinogen levels than women. Plasma creatinine and albumin were also higher in men. Urinary RAAS components showed no sexual dimorphism, whereas urinary creatinine and albumin were higher in men. Angiotensin-converting enzyme inhibitors and angiotensin II type 1 receptor blockers increased plasma renin and decreased plasma angiotensinogen, without altering plasma aldosterone. In contrast, in urine, these drugs decreased renin and aldosterone without affecting angiotensinogen. When analyzing all patients together, urinary angiotensinogen excretion closely mimicked that of albumin, whereas urinary angiotensinogen and albumin levels both were 0.05% or less of their concomitant plasma levels. This may reflect the identical glomerular filtration and tubular handling of both proteins, which have a comparable molecular weight. In contrast, urinary renin excretion did not correlate with urinary albumin excretion, and the urinary/plasma concentration ratio of renin was more than 200 times the ratio of albumin, despite its comparable molecular weight. Urinary aldosterone excretion closely followed urinary creatinine excretion. The increased urinary renin levels in diabetes and the decreased urinary renin levels following RAAS blockade, occurring independently of changes in plasma renin, reflect the activated renal RAAS in diabetes and the success of RAAS blockade in the kidney, respectively. Urinary renin, therefore, more closely reflects renal RAAS activity than urinary angiotensinogen or aldosterone.

Regulation of a novel angiotensin II precursor, proangiotensin-12, in the tissues by blockade of the renin–angiotensin system

Regulation of a novel angiotensin II precursor, proangiotensin-12, in the tissues by blockade of the renin–angiotensin system

Urinary angiotensinogen as a predictive marker in patients with immunoglobulin A nephropathy

The intrarenal renin-angiotensinogen system (RAS) plays a major role in the progression of chronic kidney disease. Urinary angiotensinogen (UAGT) provides a specific index of the intrarenal RAS status. This study was conducted to find the role of UAGT as a predictive marker in patients with immunoglobulin A nephropathy (IgAN). Thirty-six patients with IgAN, 14 non-IgAN and 15 healthy controls were included. The UAGT concentration was measured using human ELISA kits and adjusted by urinary creatinine. UAGT levels were significantly higher in patients with IgAN and non-IgAN than in healthy subjects (104.96 vs. 6.71ng/mgCr, p<0.01). Using univariate regression analysis, UAGT was found to correlate with the urine protein-to-creatinine ratio (UPCR), serum creatinine, and systolic and diastolic blood pressure in patients with IgAN. Multivariate regression analysis revealed that UAGT correlated positively with UPCR. Patients with levels of UAGT >100ng/mgCr showed higher serum creatinine after treatment than patients with UAGT levels <100ng/mgCr. This study showed that UAGT levels are increased and correlate positively with the UPCR in IgAN. Patients with high levels of UAGT may have poor renal function following treatment.

Altered urinary excretion of aquaporin 2 in IgA nephropathy

The intrarenal renin-angiotensin system (RAS) activation plays a pivotal role in immunoglobulin A nephropathy (IgAN) pathogenesis, which is still largely undefined. Recently, vasopressin (AVP) has been advocated to contribute to the genesis and progression of chronic kidney diseases (CKD) directly, and indirectly, via RAS activation. Our aim is to explore the intrarenal activity of AVP, its relationship with RAS activity, as well as its modulation by therapies in IgAN. In this observational study, we measured plasma copeptin, a surrogate marker of AVP, the urine excretion of aquaporin 2 (AQP2), a protein reflecting renal AVP action, and angiotensinogen (AGT), a parameter of renal RAS activation, and their relationship with renal function in 44 IgAN patients at the time of renal biopsy, without any drug therapy, and after 6-month treatment with ACEi or steroid+ACEi. Twenty-one patients with other CKD and 40 healthy subjects were recruited as controls. ELISAs were used to measure all variables of interest. At baseline, IgAN patients showed higher urinary levels of AQP2, compared with controls and patients with other CKD. Urinary AQP2 and AGT levels strongly correlated with the presence of arterial hypertension. Steroids+ACEi caused the decrease of all the variables examined. The fall of urinary AQP2 and AGT following drug treatments was associated with the decrease of daily proteinuria. Our findings would support the involvement of AVP-AQP2 axis, interacting with the RAS, in the progression of IgAN and candidate AQP2 as a possible novel marker of the disease.

Urinary angiotensinogen levels reflect the severity of renal histopathology in patients with chronic kidney disease

Recent studies have suggested that urinary angiotensinogen (AGT) reflects the activity of the intrarenal renin angiotensin system (RAS), which is involved in tissue injury in patients with chronic kidney disease. In this study, we investigated whether urinary AGT directly reflected the severity of histopathology in such patients. AGT was measured using a sandwich enzyme-linked immunosorbent assay (ELISA) on urine and plasma samples obtained from 58 patients on the day of renal biopsy. We measured the urinary transforming growth factor (TGF)-beta1, a representative cytokine of fibrogenic property, and analyzed the correlation among urinary TGF-beta1, urinary AGT, and the severity of renal injury. Mesangial proliferation, glomerulosclerosis, tubular atrophy and interstitial fibrosis were scored for the biopsied tissues. Urinary AGT levels correlated positively with proteinuria, urinary TGF-beta1 levels and diastolic blood pressure, but negatively with the estimated glomerular filtration rate (GFR). Urinary AGT concentrations were increased in patients with severe glomerulosclerosis, tubular atrophy and interstitial fibrosis. Urinary AGT levels correlated with the deterioration of renal function in patients with chronic kidney disease and reflected the histological severity of renal injury.

Relationship Between Urinary Angiotensinogen and Salt Sensitivity of Blood Pressure in Patients With IgA Nephropathy

We demonstrated previously that the blood pressure of patients with IgA nephropathy becomes salt sensitive as renal damage progresses. We also showed that increased urinary angiotensinogen levels in such patients closely correlate with augmented renal tissue angiotensinogen gene expression and angiotensin II levels. Here, we investigated the relationship between urinary angiotensinogen and salt sensitivity of blood pressure in patients with IgA nephropathy. Forty-one patients with IgA nephropathy consumed an ordinary salt diet (12 g/d of NaCl) for 1 week and a low-salt diet (5 g/d of NaCl) for 1 week in random order. The salt-sensitivity index was calculated as the reciprocal of the slope of the pressure-natriuresis curve drawn by linking 2 data points obtained during consumption of each diet. The urinary angiotensinogen:creatinine ratio was significantly higher in patients who consumed the ordinary salt diet compared with the low-salt diet (17.5 μg/g [range: 7.3 to 35.6 μg/g] versus 7.9 μg/g [range: 3.1 to 14.2 μg/g] of creatinine, respectively; P<0.001). The sodium sensitivity index in our patients positively correlated with the glomerulosclerosis score (r=0.43; P=0.008) and changes in logarithmic urinary angiotensinogen:creatinine ratio (r=0.37; P=0.017) but not with changes in urinary protein excretion (r=0.18; P=0.49). In contrast, changes in sodium intake did not alter the urinary angiotensinogen:creatinine ratio in patients with Ménière disease and normal renal function (n=9). These data suggest that the inappropriate augmentation of intrarenal angiotensinogen induced by salt and associated renal damage contribute to the development of salt-sensitive hypertension in patients with IgA nephropathy.

Urinary proteomics analysis for renal injury in hypertensive disorders of pregnancy with iTRAQ labeling and LC‐MS/MS

As a noninvasive examination, urinary proteomics is a very useful tool to identify renal disease. The purpose of the present study was to find differential proteins among women with preeclampsia, gestational hypertension and normal pregnancy, and to screen potential biomarkers for the early diagnosis of preeclampsia. Urinary proteins were identified by iTRAQ labeling coupled with 2-D LC-MS/MS. The bioinformatics analysis was performed with the Metacore software and the International Protein Index (IPI) and the Gene Ontology (GO) Database. The differentially expressed proteins were verified by ELISA. 362 nonredundant proteins were identified, 113 of which were expressed differentially between preeclampsia and normal pregnant group and 31 differential proteins among three groups. These differential proteins were associated with biological processes of blood coagulation, cell adhesion and differentiation, immune response and cytoskeleton development, etc. They interacted with each other in the network. The urinary angiotensinogen (AGT) was downregulated, which was consistent with the ELISA validation results. The present study found a multitude of differential proteins that might provide a clue for investigating the mechanism of proteinuria development in preeclampsia. Low urinary angiotensinogen levels were useful for identifying preeclampsia.

Urinary Angiotensinogen as a Biomarker of Nephropathy in Childhood

While most circulating angiotensinogen (AGT) is synthesized in the liver, the kidneys also produce AGT. Recently, we reported that urinary AGT is mainly originated from AGT. Using newly developed human AGT ELISA, we measured urinary AGT levels in chronic glomerulonephritis (GN) patients and patients with type 1 diabetes in childhood. Urinary AGT level was positively correlated with diastolic blood pressure, urinary albumin, urinary protein levels, and urinary occult blood in chronic GN patients. Furthermore, urinary AGT level was significantly increased in chronic GN patients not treated with renin-angiotensin system (RAS) blockers compared with control subjects. Importantly, patients treated with RAS blockers had a marked attenuation of this increase. Also, urinary AGT level was significantly higher in patients with diabetic nephropathy in the premicroalbuminuric phase than in control subjects. These results suggest that urinary AGT reflects intrarenal RAS status in chronic GN and may be an early marker of diabetic nephropathy.

Comments on Point:Counterpoint: The dominant contributor to systemic hypertension: Chronic activation of the sympathetic nervous system vs. Activation of the intrarenal renin-angiotensin system

Comments on Point:Counterpoint: The dominant contributor to systemic hypertension: Chronic activation of the sympathetic nervous system vs. Activation of the intrarenal renin-angiotensin system

Blood Pressure Characteristics of Female Spontaneously Diabetic Torii-Leprfa Rats

Blood pressure in female SDT-fa/fa rats was periodically investigated at ages 8, 16, and 24 weeks. Furthermore, an insulin therapy was performed for 5 weeks in the female rats at age 11 weeks, and the change of blood pressure was examined. In addition to obesity, hyperglycemia, hyperinsulinemia, and hyperlipidemia, hyperleptinemia and increased urinary angiotensinogen level were observed during the experimental period. Blood pressure was elevated at ages 8 and 16 weeks, but that at 24 weeks was comparable to that in Sprague-Dawley (SD) rats. Heart rate was decreased from age 8 to 24 weeks. Insulin therapy induced good glycemic control and improvement of hyperlipidemia, but the blood pressure was not reduced. Blood pressure in female SDT-fa/fa rats was elevated temporarily. The blood pressure was not decreased by insulin treatment. SDT-fa/fa rat is a useful model to investigate the relation between diabetes mellitus and hypertension.

Urinary angiotensinogen reflects the activity of intrarenal renin-angiotensin system in patients with IgA nephropathy

A potential contribution of local activation of the renin-angiotensin system (RAS) to the pathogenesis of renal injury has been indicated by evidence for blood pressure-independent renoprotective effects of angiotensin II (AngII) receptor blockers (ARBs). The present study was performed to test the hypothesis that urinary angiotensinogen provides a specific index of intrarenal RAS status in patients with immunoglobulin A (IgA) nephropathy. This paper is a survey of urine specimens from three groups: healthy volunteers, patients with IgA nephropathy and patients with minor glomerular abnormality (MGA). Patients with hypertension, diabetes, reduced glomerular filtration rate and/or who were under any medication were excluded from this study. Urinary angiotensinogen levels were measured by a sandwich enzyme-linked immunosorbent assay system. Urinary angiotensinogen levels were not different between healthy volunteers and patients with MGA. However, urinary angiotensinogen levels, renal tissue angiotensinogen expression and AngII immunoreactivity were significantly higher in patients with IgA nephropathy than in patients with MGA. Baseline urinary angiotensinogen levels were positively correlated with renal angiotensinogen gene expression and AngII immunoreactivity but not with plasma renin activity or the urinary protein excretion rate. In patients with IgA nephropathy, treatment with an ARB, valsartan (40 mg/day), significantly increased renal plasma flow and decreased filtration fraction, which were associated with reductions in urinary angiotensinogen levels. These data indicate that urinary angiotensinogen is a powerful tool for determining intrarenal RAS status and associated renal derangement in patients with IgA nephropathy.

Urinary angiotensinogen is correlated with blood pressure in men (Bogalusa Heart Study)

The Bogalusa Heart Study is a long-term study on cardiovascular disease and has followed a biracial (black/white) population from childhood. Risk factor data pertaining to many patients have been collected over 35 years, and the time course of hypertension has been documented by repeated examinations and measurements. Considerable sex and racial differences have been found to be related to cardiovascular disease. Urinary angiotensinogen (UAGT) is a novel biomarker for the intrarenal activity of the renin-angiotensin system in hypertension and kidney disease. We aimed to determine the relationship of UAGT with traditional cardiovascular disease risk factors in asymptomatic young adults in this biracial population. We recruited 251 individuals and collected a single random spot urine sample from each one. Because UAGT is significantly increased in diabetic patients and the use of antihypertensive drugs affects UAGT levels, we excluded patients who had diabetes, who were receiving antihypertensive treatment, or both. Consequently, 190 participants were included for this analysis. UAGT levels did not differ with race or sex, but were significantly correlated with SBP (r = +0.23, P = 0.0015) and DBP (r = +0.24, P = 0.0012). Moreover, high correlations were shown in men, especially in black men (SBP, r = +0.85, P = 0.0005 and DBP, r = +0.72, P = 0.0079). Thus, UAGT is correlated with blood pressure in men, even when they do not show overt proteinuria or albuminuria. The biomarker, UAGT, may facilitate the identification of individuals that are at increased risk for the development of hypertension and early asymptomatic renal disease.

Urinary Angiotensinogen Accurately Reflects Intrarenal Renin-Angiotensin System Activity

Background: We recently reported that immunoreactivity of intrarenal angiotensinogen (AGT) is significantly increased in IgA nephropathy patients. Meanwhile, we have developed direct enzyme-linked immunosorbent assays to measure plasma and urinary AGT (UAGT) in humans. This study was performed to test the hypothesis that UAGT levels are increased in chronic glomerulonephritis patients. Methods: We analyzed 100 urine samples from 70 chronic glomerulonephritis patients (26 from IgA nephropathy, 24 from purpura nephritis, 8 from lupus nephritis, 7 from focal segmental glomerulosclerosis, and 5 from non-IgA mesangial proliferative glomerulonephritis) and 30 normal control subjects. Results: UAGT–creatinine ratio (UAGT/UCre) was correlated positively with diastolic blood pressure (p = 0.0326), urinary albumin–creatinine ratio (p < 0.0001), urinary protein–creatinine ratio (p < 0.0001) and urinary occult blood (p = 0.0094). UAGT/UCre was significantly increased in chronic glomerulonephritis patients not treated with renin-angiotensin system (RAS) blockers compared with control subjects (p < 0.0001). Importantly, glomerulonephritis patients treated with RAS blockers had a marked attenuation of this augmentation (p = 0.0021). Conclusion: These data indicate that UAGT are increased in chronic glomerulonephritis patients and treatment with RAS blockers suppressed UAGT. The efficacy of RAS blockade to reduce the intrarenal RAS activity can be confirmed by measurement of UAGT in chronic glomerulonephritis patients.

Increased Urinary Angiotensinogen Is Precedent to Increased Urinary Albumin in Patients With Type 1 Diabetes

BackgroundWe previously reported that kidney and urinary angiotensinogen levels were significantly increased before the development of diabetic nephropathy in diabetic rats. To address this system in humans, we have developed an enzyme-linked immunosorbent assay for human angiotensinogen and reported that urinary excretion of angiotensinogen levels is enhanced in patients with chronic kidney disease, including patients with type 2 diabetes. On the basis of these findings, this study was performed to demonstrate that urinary angiotensinogen levels increased before the onset of microalbuminuria and that urinary angiotensinogen can be an early biomarker of intrarenal renin-angiotensin system status in normoalbuminuric patients with type 1 diabetes compared with age- and sex-matched control subjects. MethodsThe study included 28 patients with type 1 diabetes and 21 control subjects. No subject received renin-angiotensin system blockades. Random spot urine samples as well as blood samples were obtained and analyzed. ResultsUrinary albumin:creatinine ratio or urinary protein:creatinine ratio did not increase in patients compared with control subjects, suggesting that these patients were in their premicroalbuminuric phase of diabetic nephropathy. However, the urinary angiotensinogen:creatinine ratio was significantly higher in patients than in control subjects (12.1±3.2μg/g versus 4.2±0.7μg/g). Importantly, an increase in plasma angiotensinogen levels was not observed (26.3±1.3μg/mL versus 29.5±3.3μg/mL). ConclusionsThus, in patients, an increase in urinary angiotensinogen levels is observed, and this increase is precedent to an increase in urinary albumin levels, suggesting that urinary angiotensinogen may function as an early marker of diabetic nephropathy.

Urinary Angiotensinogen as a Novel Biomarker of the Intrarenal Renin-Angiotensin System Status in Hypertensive Patients

We reported previously that urinary angiotensinogen (UAGT) levels provide a specific index of the intrarenal renin-angiotensin system (RAS) status in angiotensin II-dependent hypertensive rats. To study this system in humans, we recently developed a human angiotensinogen ELISA. To test the hypothesis that UAGT is increased in hypertensive patients, we recruited 110 adults. Four subjects with estimated glomerular filtration levels <30 mL/min per 1.73 m(2) were excluded because previous studies have already shown that UAGT is highly correlated with estimated glomerular filtration in this stage of chronic kidney disease. Consequently, 106 paired samples of urine and plasma were analyzed from 70 hypertensive patients (39 treated with RAS blockers [angiotensin-converting enzyme inhibitors or angiotensin II type 1 receptor blockers; systolic blood pressure: 139+/-3 mm Hg] and 31 not treated with RAS blockers [systolic blood pressure: 151+/-4 mm Hg]) and 36 normotensive subjects (systolic blood pressure: 122+/-2 mm Hg). UAGT, normalized by urinary concentrations of creatinine, were not correlated with race, gender, age, height, body weight, body mass index, fractional excretion of sodium, plasma angiotensinogen levels, or estimated glomerular filtration. However, UAGT/urinary concentration of creatinine was significantly positively correlated with systolic blood pressure, diastolic blood pressure, urinary albumin:creatinine ratio (r=0.5994), and urinary protein:creatinine ratio (r=0.4597). UAGT/urinary concentration of creatinine was significantly greater in hypertensive patients not treated with RAS blockers (25.00+/-4.96 microg/g) compared with normotensive subjects (13.70+/-2.33 microg/g). Importantly, patients treated with RAS blockers exhibited a marked attenuation of this augmentation (13.26+/-2.60 microg/g). These data indicate that UAGT is increased in hypertensive patients, and treatment with RAS blockers suppresses UAGT, suggesting that the efficacy of RAS blockade to reduce the intrarenal RAS activity can be assessed by measurements of UAGT.

Urinary angiotensinogen as a potential biomarker of severity of chronic kidney diseases

We previously reported that urinary excretion rates of angiotensinogen (AGT) provide a specific index of the activity of the intrarenal renin-angiotensin system in angiotensin II-dependent hypertensive rats. Meanwhile, we have recently developed direct enzyme-linked immunosorbent assays (ELISAs) to measure plasma and urinary AGT in humans. This study was performed to test a hypothesis that urinary AGT levels are enhanced in chronic kidney disease (CKD) patients and correlated with some clinical parameters. Eighty patients with CKD (37 women and 43 men, from 18 to 94 years old) and seven healthy volunteers (two women and five men, from 27 to 43 years old) were included. Plasma AGT levels showed a normal distribution; however, urinary AGT-creatinine ratios (UAGT/UCre) deviated from the normal distribution. When a logarithmic transformation was executed, Log(UAGT/UCre) levels showed a normal distribution. Therefore, Log(UAGT/UCre) levels were used for further analyses. Log(UAGT/UCre) levels were not correlated with age, gender, height, body weight, body mass index, systolic blood pressure, diastolic blood pressure, serum sodium levels, serum potassium levels, urinary sodium-creatinine ratios, plasma renin activity, or plasma AGT levels. However, Log(UAGT/UCre) levels were significantly correlated positively with urinary albumin-creatinine ratios, fractional excretion of sodium, urinary protein-creatinine ratios, and serum creatinine, and correlated negatively with estimated glomerular filtration rate. Log(UAGT/UCre) levels were significantly increased in CKD patients compared with control subjects (1.8801 ± 0.0885 vs. 0.9417 ± 0.1048; P = .0024). These data confirmed our earlier report and showed that a new ELISA assay is a valid approach for measuring urinary AGT.

Determination of plasma and urinary angiotensinogen levels in rodents by newly developed ELISA

We recently reported that urinary excretion rates of angiotensinogen provide a specific index of the intrarenal renin-angiotensin system status in angiotensin II-dependent hypertensive rats. Angiotensinogen concentrations in mouse plasma are thought to be much lower than those in rat plasma; however, detailed information is deficient due to lack of direct quantitative measurements of rodent angiotensinogen. To elucidate this issue, we have developed a quantitative method for measurement of rodent angiotensinogen using a sandwich-type ELISA. The standard curve for mouse and rat angiotensinogen exhibited a high linearity at 0.16-10 and 0.08-5 ng/ml, respectively, with correlation coefficients >0.99. While plasma angiotensinogen concentrations of male high serum IgA (HIGA) mice (IgA nephritis model animals, 1,308 +/- 47 ng/ml; n = 10) were lower than those of control BALB/c mice (1,620 +/- 384; n = 12), urinary angiotensinogen concentrations of HIGA mice (14.6 +/- 1.5 ng/ml; n = 34) were higher than those of BALB/c mice (4.6 +/- 0.1; n = 2). In a similar manner, while plasma angiotensinogen concentrations of Zucker diabetic fatty (ZDF) obese rats (type 2 diabetic model animals, 1,789 +/- 50 ng/ml; n = 5) were lower than those of control ZDF lean rats (2,296 +/- 47; n = 5), urinary angiotensinogen concentrations of ZDF obese rats (88.2 +/- 11.4 ng/ml; n = 15) were higher than those of ZDF lean rats (31.3 +/- 1.9; n = 15). These data indicate that plasma and urinary angiotensinogen concentrations are less in mice than rats. However, these data suggest that urinary angiotensinogen levels are different from plasma angiotensinogen levels in rodents. The development of rodent angiotensinogen ELISA allows quantitative comparisons in mouse and rat angiotensinogen levels in models of hypertension and cardiovascular and kidney diseases.