The protective arm of the renin -angiotensin system may counteract the intense inflammatory process in fetuses with posterior urethral valves / O braço protetor do sistema renina-angiotensina pode contrapor-se ao intenso processo inflamatório em fetos com válvula de uretra posterior

Abstract Objective: Posterior urethral valve is the most common lower urinary tract obstruction in male children. A high percentage of patients with posterior urethral valve evolve to end‐stage renal disease. Previous studies showed that cytokines, chemokines, and components of the renin-angiotensin system contribute to the renal damage in obstructive uropathies. The authors recently found that urine samples from fetuses with posterior urethral valve have increased levels of inflammatory molecules. The aim of this study was to measure renin-angiotensin system molecules and to investigate their correlation with previously detected inflammatory markers in the same urine samples of fetuses with posterior urethral valve. Methods: Urine samples from 24 fetuses with posterior urethral valve were collected and compared to those from 22 healthy male newborns at the same gestational age (controls). Renin-angiotensin system components levels were measured by enzyme‐linked immunosorbent assay. Results: Fetuses with posterior urethral valve presented increased urinary levels of angiotensin (Ang) I, Ang‐(1‐7) and angiotensin‐converting enzyme 2 in comparison with controls. ACE levels were significantly reduced and Ang II levels were similar in fetuses with posterior urethral valve in comparison with controls. Conclusions: Increased urinary levels of angiotensin‐converting enzyme 2 and of Ang‐(1‐7) in fetuses with posterior urethral valve could represent a regulatory response to the intense inflammatory process triggered by posterior urethral valve.

Resumo Objetivo: A válvula de uretra posterior é a obstrução do trato urinário inferior mais comum em crianças do sexo masculino. Uma alta porcentagem de pacientes com válvula de uretra posterior evolui para doença renal em estágio final. Estudos anteriores mostraram que citocinas, quimiocinas e componentes do sistema renina-angiotensina contribuem para o dano renal em uropatias obstrutivas. Recentemente, descobrimos que amostras de urina de fetos com válvula de uretra posterior tinham níveis aumentados de moléculas inflamatórias. O objetivo deste estudo foi medir as moléculas de renina-angiotensina e investigar sua correlação com marcadores inflamatórios previamente detectados nas mesmas amostras de urina de fetos com válvula de uretra posterior. Métodos: Amostras de urina de 24 fetos com válvula de uretra posterior foram coletadas e comparadas com amostras de urina de 22 recém-nascidos saudáveis de mesma idade gestacional (controles). Os níveis dos componentes de SRA foram medidos por ensaio de imunoabsorção enzimática. Resultados: Os fetos com válvula de uretra posterior apresentaram níveis urinários aumentados de angiotensina (Ang) I, Ang-(1-7) e enzima conversora de angiotensina 2 em comparação com os controles. Os níveis de enzima conversora de angiotensina eram significativamente menores e os níveis de Ang II eram semelhantes nos fetos com válvula de uretra posterior em comparação com os controles. Conclusões: O aumento dos níveis urinários de enzima conversora de angiotensina 2 e de Ang-(1-7) em fetos com válvula de uretra posterior poderia representar uma resposta regulatória ao intenso processo inflamatório desencadeado pela válvula de uretra posterior.

Increased urinary angiotensin converting enzyme 2 and neprilysin in patients with type 2 diabetes.

Angiotensin converting enzyme 2 (ACE2) and neprilysin (NEP) are metalloproteases that are highly expressed in the renal proximal tubules. ACE2 and NEP generate renoprotective angiotensin (1-7) from angiotensin II and angiotensin I, respectively, and therefore could have a major role in chronic kidney disease (CKD). Recent data demonstrated increased urinary ACE2 in patients with diabetes with CKD and kidney transplants. We tested the hypothesis that urinary ACE2, NEP, and a disintegrin and metalloproteinase 17 (ADAM17) are increased and could be risk predictors of CKD in patients with diabetes. ACE2, NEP, and ADAM17 were investigated in 20 nondiabetics (ND) and 40 patients with diabetes with normoalbuminuria (Dnormo), microalbuminuria (Dmicro), and macroalbuminuria (Dmacro) using ELISA, Western blot, and fluorogenic and mass spectrometric-based enzyme assays. Logistic regression model was applied to predict the risk prediction. Receiver operating characteristic curves were drawn, and prediction accuracies were calculated to explore the effectiveness of ACE2 and NEP in predicting diabetes and CKD. Results demonstrated that there is no evidence of urinary ACE2 and ADAM17 in ND subjects, but both enzymes were increased in patients with diabetes, including Dnormo. Although there was no detectable plasma ACE2 activity, there was evidence of urinary and plasma NEP in all the subjects, and urinary NEP was significantly increased in Dmicro patients. NEP and ACE2 showed significant correlations with metabolic and renal characteristics. In summary, urinary ACE2, NEP, and ADAM17 are increased in patients with diabetes and could be used as early biomarkers to predict the incidence or progression of CKD at early stages among individuals with type 2 diabetes.

Measurement of Angiotensin Converting Enzyme 2 Activity in Biological Fluid (ACE2).

Angiotensin-converting enzyme 2 (ACE2) is a recently described member of the renin-angiotensin system that hydrolyzes angiotensin (Ang) II to Ang-(1-7), and may thereby protect against cardiovascular and renal diseases. ACE2 is a type 1 integral membrane protein and contains a catalytically active ectodomain that can be shed from the cell surface into the extracellular space, via cleavage by a disintegrin and metalloproteinase-17 (ADAM-17). ACE2 enzymatic activity and protein can be detected in biological fluids, including urine, plasma, and conditioned cell culture media. We present a detailed method for measurement of ACE2 activity in biological fluids, using hydrolysis of an intramolecularly quenched fluorogenic ACE2 substrate, in the absence or presence of the ACE2 inhibitors MLN-4760 or DX600. Recombinant human or mouse ACE2 is used to generate standard curves for this assay, with ACE2 detection ranging from 1.56 to 50 ng/ml. While MLN-4760 potently inhibits the activity of both human and mouse ACE2, DX600 (linear form) only effectively blocks human ACE2 activity in this assay. In biological samples of human and mouse urine, cell culture medium from mouse proximal tubular cells, and mouse plasma, the mean intra- and inter-assay coefficients of variation (CVs) of the assay range from 1.43 to 4.39 %, and from 7.01 to 13.17 %, respectively. We present data on the time and substrate concentration dependence of the assay, and show that exogenous D -glucose, creatinine, urea, and albumin do not interfere with its performance. In biological fluids, this assay is a simple and reliable method to study the role of ACE2 and its shed fragments in cardiovascular and renal diseases.

Insulin treatment attenuates renal ADAM17 and ACE2 shedding in diabetic Akita mice.

Angiotensin-converting enzyme 2 (ACE2) is located in several tissues and is highly expressed in renal proximal tubules, where it degrades the vasoconstrictor angiotensin II (ANG II) to ANG-(1-7). Accumulating evidence supports protective roles of ACE2 in several disease states, including diabetic nephropathy. A disintegrin and metalloprotease (ADAM) 17 is involved in the shedding of several transmembrane proteins, including ACE2. Our previous studies showed increased renal ACE2, ADAM17 expression, and urinary ACE2 in type 2 diabetic mice (Chodavarapu H, Grobe N, Somineni HK, Salem ES, Madhu M, Elased KM. PLoS One 8: e62833, 2013). The aim of the present study was to determine the effect of insulin on ACE2 shedding and ADAM17 in type 1 diabetic Akita mice. Results demonstrate increased renal ACE2 and ADAM17 expression and increased urinary ACE2 fragments (≈70 kDa) and albumin excretion in diabetic Akita mice. Immunostaining revealed colocalization of ACE2 with ADAM17 in renal tubules. Renal proximal tubular cells treated with ADAM17 inhibitor showed reduced ACE2 shedding into the media, confirming ADAM17-mediated shedding of ACE2. Treatment of Akita mice with insulin implants for 20 wk normalized hyperglycemia and decreased urinary ACE2 and albumin excretion. Insulin also normalized renal ACE2 and ADAM17 but had no effect on tissue inhibitor of metalloproteinase 3 (TIMP3) protein expression. There was a positive linear correlation between urinary ACE2 and albuminuria, blood glucose, plasma creatinine, glucagon, and triglycerides. This is the first report showing an association between hyperglycemia, cardiovascular risk factors, and increased shedding of urinary ACE2 in diabetic Akita mice. Urinary ACE2 could be used as a biomarker for diabetic nephropathy and as an index of intrarenal ACE2 status.

Rosiglitazone treatment of type 2 diabetic db/db mice attenuates urinary albumin and angiotensin converting enzyme 2 excretion.

Alterations within the renal renin angiotensin system play a pivotal role in the development and progression of cardiovascular and renal disease. Angiotensin converting enzyme 2 (ACE2) is highly expressed in renal tubules and has been shown to be renoprotective in diabetes. The protease, a disintegrin and metalloprotease (ADAM) 17, is involved in the ectodomain shedding of several transmembrane proteins including ACE2. Renal ACE2 and ADAM17 were significantly increased in db/db mice compared to controls. We investigated the effect of the insulin sensitizer, rosiglitazone, on albuminuria, renal ADAM17 protein expression and ACE2 shedding in db/db diabetic mice. Rosiglitazone treatment of db/db mice normalized hyperglycemia, attenuated renal injury and decreased urinary ACE2 and renal ADAM17 protein expression. Urinary excreted ACE2 is enzymatically active. Western blot analysis of urinary ACE2 demonstrated two prominent immunoreactive bands at approximately 70 & 90 kDa. The predominant immunoreactive band is approximately 20 kDa shorter than the one demonstrated for kidney lysate, indicating possible ectodomain shedding of active renal ACE2 in the urine. Therefore, it is tempting to speculate that renoprotection of rosiglitazone could be partially mediated via downregulation of renal ADAM17 and ACE2 shedding. In addition, there was a positive correlation between blood glucose, urinary albumin, plasma glucagon, and triglyceride levels with urinary ACE2 excretion. In conclusion, urinary ACE2 could be used as a sensitive biomarker of diabetic nephropathy and for monitoring the effectiveness of renoprotective medication.

Urinary angiotensin-converting enzyme 2 in patients with CKD.

AIM: Angiotensin-converting enzyme 2 (ACE2) is a type I membrane protein that antagonizes the action of angiotensin II. Because of the need for invasive kidney biopsy, little is known about the role of renal ACE2 in human kidney diseases. The authors studied if urinary ACE2 could provide a novel clue to renal ACE2 in chronic kidney disease (CKD). METHODS: Subjects were 190 patients with CKD including 38 patients with diabetic nephropathy and 36 healthy subjects. Parameters were urinary ACE2 by enzyme-linked immunosorbent assay, blood pressure, casual plasma glucose, proteinuria, microalbuminuria, serum creatinine and estimated glomerular filtration rate. Urine and serum samples were also subjected to western blotting of ACE2. RESULTS: Western blotting confirmed increased urinary ACE2 levels in patients with CKD. Urinary ACE2 was significantly higher in patients with CKD than healthy subjects (median 9.64 (interquartile range, 4.41-16.89) vs 1.50 (0.40-2.33) mg/g·creatinine, P < 0.001) and in patients with diabetic nephropathy than patients without diabetic nephropathy (median 13.16 (interquartile range 6.81-18.70) vs 8.90 (4.19-16.67) mg/g·creatinine, P < 0.05). No significant difference in urinary ACE2 was observed by the use of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker. CONCLUSION: Urinary ACE2 could be used as a non-invasive marker to understand the role of renal ACE2 in CKD.

Association of urinary 90 kDa angiotensin- converting enzyme with family history of hypertension and endothelial function in normotensive individuals

We described angiotensin-I-converting enzyme (ACE) isoforms with molecular masses of 190, 90, and 65 kDa in the urine of normotensive offspring of hypertensive subjects. Since they did not appear in equal amounts, we suggested that 90 kDa ACE might be a marker for hypertension. We evaluated the endothelial response in normotensive offspring with or without family history of hypertension and its association with the 90 kDa ACE in urine. Thirty-five normotensive subjects with a known family history of hypertension and 20 subjects without a family history of hypertension, matched for age, sex, body weight, and blood pressure, were included in the study. Endothelial function was assessed by ultrasound and a sample of urine was collected for determination of ACE isoforms. In the presence of a family history of hypertension and detection of 90 kDa ACE, we noted a maximal flow mediated dilation of 12.1 ± 5.0 vs 16.1 ± 6.0 percent in those without a previous history of hypertension and lacking urinary 90 kDa ACE (P < 0.05). In subjects with a family history of hypertension and presenting 90 kDa ACE, there were lower levels of HDL-cholesterol (P < 0.05) and higher levels of triglycerides (P < 0.05). Subjects with 90 kDa ACE irrespective of hypertensive history presented a trend for higher levels of triglycerides and HDL-cholesterol (P = 0.06) compared to subjects without 90 kDa ACE. Our data suggest that the 90 kDa ACE may be a marker for hypertension which may be related to the development of early atherosclerotic changes.

Increased activity of plasma and tissue kallikreins, plasma kininase II and salivary kallikrein in pemphigus foliaceus (fogo selvagem).

BACKGROUND: Pemphigus foliaceus (PF) is an autoimmune blistering disease of unknown aetiology, which is endemic in Brazil. Although the pathogenesis of PF is still unknown, proteins of the contact system have been implicated. OBJECTIVES: As the components of the kinin system may interact with those of the contact system, in this study we evaluated the plasma levels of high-molecular-weight kininogen (HK) and low-molecular-weight kininogen (LK), and the activity of plasma kallikrein, tissue kallikrein and kininase II in plasma of patients with PF presenting with Nikolsky's sign. As kidneys and salivary glands are relevant sources of tissue kallikrein for plasma, we also evaluated urinary/salivary kallikrein and urinary kininase II activities. METHODS: Fifteen patients and 15 age- and sex-matched controls were studied. Kininogen levels were determined by enzyme-linked immunosorbent assay, and the activities of kallikreins and kininase II were determined using selective chromogenic substrates. RESULTS: Compared with controls, plasma HK levels were decreased (P = 0.031), whereas the activities of plasma kallikrein, tissue kallikrein and kininase II in plasma, and the activity of salivary kallikrein, were increased in patients (P < 0.001 for each comparison). Plasma levels of LK and the activities of urinary kallikrein and urinary kininase II were not significantly different from controls. CONCLUSIONS: Diminished levels of HK associated with increased activities of plasma kallikrein and kininase II indicate that the kinin system is activated at the systemic level in PF. As active plasma kallikreins may act on some proteins of the contact system, it is possible that the enzyme may contribute to blister formation. The further observation of an increased tissue kallikrein activity at the systemic and saliva levels may be interpreted as a systemic reflex of skin inflammation. Whether the activation of the kinin system is a cause or a consequence of blister formation needs further clarification.

Kinin system in lupus nephritis.

There are few studies regarding the evaluation of the kinin system in patients with systemic lupus erythematosus (SLE). In this study, we evaluated the plasma levels of high-molecular weight kininogen (HKg), low-molecular weight kininogen (LKg) and plasma kallikrein; the plasma activity of tissue kallikrein and kininase II, and urinary kallikrein and kininase II activities in patients presenting with active lupus nephritis. A total of 30 patients (29 women) aged 21-62 years (median = 39) and 30 controls matched to the patients for sex and age were studied. Patients presenting with other underlying diseases or using drugs, which could interfere with the kinin system, were excluded. HKg and LKg levels were indirectly evaluated by ELISA. Plasma kallikrein, tissue kallikrein, and kininase II were evaluated by their enzymatic activity on selective substrates. The Mann-Whitney test was used for statistical analysis. HKg, LKg and plasma kallikrein levels were significantly increased in patients (p < 0.001, for each comparison). Similarly, tissue kallikrein and kininase II activities were significantly increased in plasma and urine of patients (p <0.001, for each comparison). In urine, the activities of tissue kallikrein and kininase II were at least seven times higher than those seen in the plasma of patients. These results indicate that the kinin system is involved in the acute manifestations of lupus nephritis. Kinins may facilitate immunecomplex deposition and may induce the release of other pro-inflammatory mediators, including cytokines actively involved in the pathogenesis of lupus nephritis.

[Changes in urinary enzyme activity following silicon therapy of vesico-ureteral reflux]. / A vizeletenzimek aktivitásváltozása vesicoureteralis reflux szilikonnal végzett kezelésében.

The urinary enzymes Gamma Glutamyl Transferase (GGT), Alkaline Phosphatase (ALP), Leucine-Arylamidase (LAS) and Dipeptidyl-Peptidase-IV (DPP-IV) were measured before and after endoscopic treatment of vesico-ureteric reflux (VUR) in two groups of twenty children's. Ten patients had undergone successful endoscopic corrective surgery for VUR, another 10 patients had unsuccessful endoscopic intervention. After successful treatment the activity of LAS in the urine did not change, but that of GGT, ALP and DDP-IV activity in the urine was 2-5 times higher than before treatment (P < 0.03 for all three enzymes). Considerable changes of urinary enzymes' activity were not observed following unsuccessful endoscopic treatment. Our data and the literature are contradictory. However this contradiction might be explained by the differences in urine sampling methods. Our patients received the same chemoprofilactic drug at the time of both urine sampling, a point not considered by other researchers. The extent of increase of enzyme activity after endoscopic treatment of VUR did not reach the level that would permit the use of investigated enzymes for screening, because the observed changes did not exceed the limits of the normal range.

[Neurohumoral, autacoid and transductional mechanisms in the cardiovascular effects of vanadate: histochemical correlations]. / Meccanismi neuroumorali, autacoidali e trasduzionali negli effetti cardiovasali di vanadato: correlati istochimici.

Rabbits given 1 ppm of vanadate in drinking water for twelve months showed (a) increased plasma levels of catecholamines (b) reduction of the arterial concentration of nitric oxide (c) lower activity of urine kallikrein and higher activities of urine kininases I and II and enkephalinase (d) reduced cardiac inotropism and augmented total peripheral resistance, with unchanged blood pressure levels (e) accumulation of the metal in the aorta and cardiac ventricles. Monoaminooxidase and glucose-6-phosphate dehydrogenase activities were increased by vanadate in both kidney and liver and that of NADH-diaphorase in the kidney, in which NADPH-diaphorase activity was reduced. Some of the above results were also obtained in rats given 10 and 40 ppm of vanadate in drinking water for six-seven months; these animals showed arterial hypertension and reduced activity of Na, K-ATPase in the kidney. Vanadium appears to act on the cardiovascular function through selective neurohumoral, autacoidal and transductional mechanisms only in part depending on the species.

Significance of renal kininases in patients with Cushing's syndrome.

To further clarify the significance of renal kininases in patients with Cushing's syndrome, daily urinary excretions of total kininase, kininase I, Ii and neutral endopeptidase 24.11 (NEP) were examined and evaluated for the relations between plasma cortisol level and these kininases. Urinary total kininase kininase I, II and NEP were significantly higher in patients with Cushing's syndrome than in normotensives. There was a significant positive correlation between plasma cortisol level and total kininase or NEP, and the same tendency was observed between plasma cortisol level and kininase I. After adrenalectomy, urinary kininases decreased to normal levels. These findings suggested that: 1) kininase I, II and NEP are accelerated in Cushing's syndrome; 2) glucocorticoids may regulate renal kininases; and 3) accelerated renal kininases may play some role in disorders of the renal water-sodium metabolism and in high blood pressure in Cushing's syndrome.

Significance of renal kininases in patients with primary aldosteronism.

To elucidate the significance of renal kininases in primary aldosteronism (PA), urinary total kininase, kininase I, II and neutral endopeptidase 24.11 (NEP) were examined and evaluated for the regulation mechanisms of these kininases. Total kininase, kininase I and NEP were significantly higher in PA than in normotensives (NT), whereas no difference was found for kininase II. Moreover, 42% of total kininase consisted of unknown kininase(s), different from kininase I, II or NEP. There were significantly positive correlations between plasma aldosterone concentration and total kininase, kininase I and unknown kininase(s) in PA. After the adrenalectomy, urinary kininases decreased into normal ranges, and unknown kininase(s) were negligible. These findings suggested that: 1) kininase I and NEP are accelerated in PA; 2) unknown kininase(s) differing from kininase I, II or NEP may exist in PA; 3) mineralocorticoids may regulate renal kininases; and 4) accelerated renal kininases may play some role in disorders of the renal water-sodium metabolism and in high blood pressure in PA.

Angiotensin I converting enzyme in glycerol-induced acute renal failure in rats.

Angiotensin I converting enzyme (ACE) activity was measured in serum, urine, and tissues of rats with acute renal failure (ARF) induced by glycerol. Glycerol-injected rats were subdivided in three groups according to the urinary volume: oliguric, nonoliguric, and polyuric. The damage to the proximal tubule was evident by (a) the histological analysis at light and electron microscopy level, (b) the augmented urinary excretion of the enzymes dipeptidyl aminopeptidase IV and N-acetyl-beta-D-glucosaminidase, and (c) the low molecular weight proteinuria pattern. On the other hand, the appearance of the glomeruli at the ultrastructural level was normal. These data suggest that the increased urinary excretion of enzymes and proteins in these rats is a consequence of the tubular injury. ARF was markedly higher in the oliguric rats. Urine ACE activity increased in the rats of the three groups, but statistical significance was reached only in the oliguric rats. Serum ACE activity increased in the oliguric rats and tissue ACE activity did not change. It is concluded that the high urinary ACE in glycerol-treated rats is associated with the damage to the kidney tubules. These data support the contention that urinary ACE may be another marker of injury to the proximal tubule.

Angiotensin I converting enzyme activity in uranyl nitrate induced acute renal failure in rats.

Angiotensin I converting enzyme (ACE) was measured in urine, serum, and tissues from rats with acute renal failure (ARF) induced by a single subcutaneous injection (15 mg/kg BW) of uranyl nitrate (UN). Urine was collected daily until day 5, when rats were sacrificed by decapitation for the obtention of blood serum and tissues. Other groups of rats were sacrificed on days 1 and 2. These rats showed proteinuria and polyuria. The damage to the kidney proximal tubule was shown by (a) histological analysis at light and electron microscopy levels on days 1, 2, and 5, (b) the increase in urinary excretion of dipeptidyl aminopeptidase IV and N-acetyl-beta-D-glucosaminidase on days 1-5, and (c) the low molecular weight proteinuria pattern on day 1. In addition, the histological analysis at the ultrastructural level showed normal glomeruli appearance on days 1 and 2, but structural alterations on day 5. These data suggest that the increased urinary excretion of enzymes and proteins is a consequence of the tubular injury on days 1 and 2, and of tubular and glomerular injury on day 5. ACE activity increased in urine on days 1-5 and in serum on day 5. Tissue ACE activity increased in lung, small intestine, and adrenal glands; and remained unchanged in testis, aorta, brain, kidney, heart, and liver. Our data suggest that: (a) the increase in serum ACE may be secondary to the changes in tissue ACE activity, and (b) the urine ACE increase may be due to the kidney proximal tubule damage. This work supports the contention that an increase in urine ACE may be an indicator of injury to the proximal tubule.

Renal toxicity and arterial hypertension in rats chronically exposed to vanadate.

The effects of 1, 10, or 40 micrograms/ml of vanadium, given for six or seven months as sodium metavanadate in drinking water on cardiovascular and biochemical variables and the electrolyte metabolism of male Sprague-Dawley rats were investigated. At the end of the exposure period, all animals exposed to vanadate had increased systolic and diastolic blood pressure. This effect was not dose dependent and heart rate and cardiac inotropism were not affected. The role of defective renal function and electrolyte metabolism in such effects was supported, in the rats exposed to 10 and 40 ppm of vanadium, by the following changes: (a) decreased Na, + K(+)-ATPase activity in the distal tubules of nephrons; (b) increased urinary excretion of potassium; (c) increase in plasma renin activity and urinary kallikrein, kininase I, and kininase II activities; (d) increased plasma aldosterone (only in the rats treated with 10 ppm of vanadium). The alterations in the rats exposed to 1 ppm of vanadium were: (a) reduced urinary calcium excretion; (b) reduced urinary kallikrein activity; (c) reduced plasma aldosterone. These results suggest that blood hypertension in rats exposed to vanadate depends on specific mechanisms of renal toxicity related to the levels of exposure.

Renal kininases in primary aldosteronism.

In order to further clarify the role of renal kallikrein-kinin (K-K) system in primary aldosteronism (PA), daily urinary excretions of renal K-K system components including kallikrein (KAL), kinin (KIN), total kininase (K-ase), K-ase I, K-ase II and neutral endopeptidase (NEP) were measured in PA and normotensives (NT). In this study, a new method for the simultaneous determination of human urinary K-ase I, II and NEP was established and employed. The daily excretions of KAL was significantly higher in PA than that in NT, while no difference was found in KIN between PA and NT. On the other hand, total K-ase in PA (897 +/- 258 micrograms/min/day) was significantly higher than that in NT (209 +/- 6). NEP was also significantly higher in PA (262 +/- 22 micrograms/min/day) than that in NT (127 +/- 6), whereas there were no differences in K-ase I and K-ase II between PA and NT. The relative contributions of K-ase I, II and NEP to total K-ase in NT were 14, 27 and 59%, while those in PA were 12, 17 and 36%, respectively. As a result, these three K-ase contributed only 64% to the total K-ase in PA. These findings suggested that 1) NEP may play a major role in the catabolism of renal KIN in human, 2) NEP is accelerated in PA, 3) unknown K-ase, different from K-ase I, II or NEP, may exist in PA, and 4) accelerated renal K-ase activity may play some role on the disorder of renal water-sodium metabolism and high blood pressure in PA.

A sensitive method for differential determination of kininase I, II and neutral endopeptidase (NEP) in human urine.

In order to clarify the significance of NEP in human renal kallikrein-kinin system, an assay system was developed for the simultaneous determination of kininase I, II and NEP activities in human. Each kininase activity was determined by measuring the hydrolysis of bradykinin in the presence of specific inhibitors of kininase I (2-mercaptomethyl-3-guanidinoethylthiopropanoic acid), kininase II (captopril) and NEP (phosphoramidon) in 8 normal subjects. The effects of the different assay buffers on kininase activities were also investigated by using a phosphate buffer. Total kininase, kininase I, II and NEP activities were 499 +/- 65 ng/min/ml (mean +/- S.E.), 55 +/- 8, 141 +/- 21 and 299 +/- 42, respectively in our method using a tris buffer, while a phosphate buffer brought about activities of 358 +/- 43, 45 +/- 5, 156 +/- 21 and 135 +/- 25 ng/min/ml. The relative contributions of kininase I, II and NEP to total kininase activity were 11, 29 and 59% in our assay system, while they were 13, 44 and 35% when a phosphate buffer was used. From these results it was suggested that 1) phosphate may inhibit urinary NEP activity, so that a tris buffer should be used as the incubation buffer, 2) NEP is the major component of human urinary kininases, and 3) NEP may play an important role in the renal kallikrein-kinin system.

Localization of neutral endopeptidase in the kidney determined by the stop-flow method.

Recently, the existence of neutral endopeptidase (NEP) as a new kininase in the kidney has been reported. In this study, the localization of NEP in the nephron was investigated and compared with other components of the renal kallikrein-kinin (K-K) system by using a stop-flow method in dog kidneys. The stop-flow method was performed according to the procedures previously reported by Scicli et al and Malvin et al. Five mongrel dogs (weighing 15-20 kg) were used in this study. Kininase I, II and NEP were measured by the modified procedure of Ura et al. Kallikrein and kinin were found in the distal tubules, and kininase I and II were observed in both the distal and proximal tubules. NEP was localized mainly in the proximal tubules. A small peak was also recognized in the distal tubules. From these results, it was suggested that, not only kininase I and II but also NEP existing in the proximal tubules may destroy kinin filtered from the glomeruli, and these kininases existing in the distal tubules may play an important role in connection with kinin producing enzymes on the regulation of activity in the renal kallikrein-kinin system.

Renal function in urinary schistosomiasis in the Natal Province of South Africa.

Renal function was assessed in 101 schoolchildren with active urinary schistosomiasis by measuring serum creatinine, urate, urea, and B2-microglobulin, urinary B2 microglobulin, and the glomerular filtration rate. Glomerular function in all subjects was normal as were serum creatinine, urate, and urea levels. Serum B2-microglobulin was elevated in only 8% of subjects while urinary B2-microglobulin only was raised in 7% of subjects, indicating proximal tubular dysfunction, a previously unreported feature in urinary schistosomiasis. Urinary tract abnormalities were found in 43% of subjects consenting to an excretory urogram but no correlation with biochemical parameters of renal function was noted. Serum angiotensin converting enzyme level measured in 70 subjects was elevated in 11% of subjects and was regarded as a possible measure of increased granulomatous activity.