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Ribeiro AA, Palomino Z, Lima MP, Souza LE, Ferreira DS, Pesquero JB, Irigoyen MC, Pesquero JL, Casarini DE. Characterization of the renal renin-angiotensin system in transgenic mice that express rat tonin. J Renin Angiotensin Aldosterone Syst 2015. [PMID: 26216430 DOI: 10.1177/1470320315595572] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
INTRODUCTION Tonin is an enzyme that is able to generate angiotensin II (Ang II) from angiotensin I (Ang I) or directly from angiotensinogen. Our goal was to characterize the renal renin-angiotensin system in transgenic mice that express rat tonin (TGM`(rTon)). MATERIALS AND METHODS Mice were euthanized and the kidneys removed for analysis. Tonin activity was evaluated by radioimmunoassay and angiotensin I-converting enzyme (ACE) activity by HPLC. Tonin, ACE and angiotensin II-converting enzyme (ACE2) expression was analyzed by Western blotting. RESULTS Tonin activity was significantly increased in TGM`(rTon) compared to their respective wild-type (WT) littermates (1.7 ± 0.21 vs 0.11 ± 0.02 nmol of Ang II/min/mg of protein). Tonin activity had a strong positive correlation with tonin expression in both TGM`(rTon) and their respective wild-type littermates. The ACE activity and expression levels of 65-kDa N-domain angiotensin I-converting enzyme isoform were significantly increased in the TGM`(rTon) when compared with WT. ACE2 expression levels were statistically significantly higher in the TGM`(rTon) when compared with WT. Angiotensin 1-7 (Ang(1-7)) and Ang I levels were significantly lower in the TGM`(rTon). CONCLUSIONS We suggest that the environment of tonin abundance may increase N-domain ACE activity liberated by a secretase able to cleave somatic ACE.
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Affiliation(s)
- Amanda A Ribeiro
- Department of Medicine, Nephrology Division, Universidade Federal de São Paulo, Escola Paulista de Medicina, Brazil
| | - Zaira Palomino
- Department of Medicine, Nephrology Division, Universidade Federal de São Paulo, Escola Paulista de Medicina, Brazil
| | - Mércia P Lima
- Department of Basic Nursing, Nursing School, Universidade Federal de Minas Gerais, Brazil
| | - Leandro E Souza
- Heart Institute, Medical School of University of São Paulo, Brazil
| | | | - João B Pesquero
- Department of Biophysics, Universidade Federal de São Paulo, Brazil
| | - Maria C Irigoyen
- Heart Institute, Medical School of University of São Paulo, Brazil
| | - Jorge L Pesquero
- Department of Biophysics, Universidade Federal de Minas Gerais, Brazil
| | - Dulce E Casarini
- Department of Medicine, Nephrology Division, Universidade Federal de São Paulo, Escola Paulista de Medicina, Brazil
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Damasceno DD, Lima MP, Motta DF, Ferreira AJ, Quintão-Junior JF, Drummond LR, Natali AJ, Almeida AP, Pesquero JL. Cardiovascular and electrocardiographic parameters after tonin administration in Wistar rats. ACTA ACUST UNITED AC 2013; 181:30-6. [PMID: 23318501 DOI: 10.1016/j.regpep.2012.12.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2012] [Revised: 10/12/2012] [Accepted: 12/17/2012] [Indexed: 10/27/2022]
Abstract
In order to understand the mechanisms of interaction between tonin-angiotensin and renin-angiotensin systems (RAS) we evaluated, "in vivo" and "in vitro", in Wistar rats, cardiovascular and electrocardiographic parameters after tonin administration. Arterial pressure (AP) and electrocardiogram (ECG) were recorded in awake animals before and after tonin administration. Langendorff technique was used to analyze cardiac function in isolated heart in the presence of tonin and video motion edge detection system was used to evaluate the effect of tonin upon contractile function of isolated rat ventricular cardiomyocytes. After tonin infusion rats presented significantly higher diastolic and mean arterial pressure (MAP) and heart rate (HR) as compared with control. The ECG analysis revealed shorter RR interval, increase in the low-frequency (LF) range of the heart rate variability (HRV) power (%) and decrease in the high-frequency (HF) of HRV power (%). Isolated hearts perfused with tonin presented an increase in the arterial coronary pressure (ACP) and decline in the ventricular systolic tension (ST), maximal (dT/dt+) and minimal (dT/dt) contractility. The rates of contraction and relaxation of isolated ventricular cardiomyocytes were significantly increased due to the presence of tonin. The angiotensin II (Ang II) levels in the coronary sinus effluent increased in the presence of tonin in a dose-dependent manner and the effect of tonin upon ACP was completely blocked by candesartan. Tonin is able to generate the vasoconstrictor peptide Ang II in the isolated heart of the rat and the cardiovascular response induced by tonin was completely blocked by candesartan, an indication that the action of Ang II on Ang II type 1 (AT1) receptors is the major mechanism of the heart effects. Tonin affects cardiomyocyte contractile function which may be due to interference with Ca(2+) handling.
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Affiliation(s)
- Denis D Damasceno
- Department of Educational Development, Federal Institute of Education, Science and Technology of Southeast Minas Gerais, Campus Barbacena, MG, Brazil.
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Goetz RM. The antiatherogenic potential of blocking the renin-angiotensin system. Expert Opin Investig Drugs 2005; 6:1651-8. [PMID: 15989569 DOI: 10.1517/13543784.6.11.1651] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Angiotensin converting enzyme (ACE) inhibitors have proved effective in preventing or ameliorating clinical manifestations of atherosclerosis, such as myocardial infarction (MI) and heart failure. Experimental evidence demonstrates their anti-atherogenic potential; ACE inhibitors do not only suppress the formation of proatherogenic angiotensin II (AII), but also enhance the formation and release of anti-atherogenic nitric oxide (NO) at local tissue sites; both mechanisms are implicated in the suppression of neointima formation in the balloon-injured vessel wall. A similar anti-atherogenic potential is provided by the blockade of the renin-angiotensin system (RAS) at the level of the angiotensin type-1 (AT1) receptor. AT1 receptor antagonists do not only block the proatherogenic actions of AII, but also induce an enhanced formation and release of anti-atherogenic NO at local tissue sites. AT1 receptor antagonists may therefore prove as effective as ACE inhibitors in patients with manifest atherosclerosis.
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Affiliation(s)
- R M Goetz
- Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 75 Francis St., Boston, MA 02115, USA
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Carey RM, Siragy HM. Newly recognized components of the renin-angiotensin system: potential roles in cardiovascular and renal regulation. Endocr Rev 2003; 24:261-71. [PMID: 12788798 DOI: 10.1210/er.2003-0001] [Citation(s) in RCA: 378] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The renin-angiotensin system (RAS) is a coordinated hormonal cascade in the control of cardiovascular, renal, and adrenal function that governs body fluid and electrolyte balance, as well as arterial pressure. The classical RAS consists of a circulating endocrine system in which the principal effector hormone is angiotensin (ANG) II. ANG is produced by the action of renin on angiotensinogen to form ANG I and its subsequent conversion to the biologically active octapeptide by ANG-converting enzyme. ANG II actions are mediated via the ANG type 1 receptor. Here, we discuss recent advances in our understanding of the components and actions of the RAS, including local tissue RASs, a renin receptor, ANG-converting enzyme-2, ANG (1-7), the function of the ANG type 2 receptor, and ANG receptor heterodimerization. The role of the RAS in the regulation of cardiovascular and renal function is reviewed and discussed in light of these newly recognized components.
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Affiliation(s)
- Robert M Carey
- Division of Endocrinology and Metabolism, Department of Medicine, University of Virginia Health System, Charlottesville, Virginia 22908, USA.
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Borges JC, Silva JA, Gomes MA, Lomez ESL, Leite KM, Araujo RC, Bader M, Pesquero JB, Pesquero JL. Tonin in rat heart with experimental hypertrophy. Am J Physiol Heart Circ Physiol 2003; 284:H2263-8. [PMID: 12543632 DOI: 10.1152/ajpheart.00416.2002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present study was undertaken to determine tonin expression and activity in rat heart presenting isoproterenol-induced hypertrophy. Renin, angiotensin-converting enzyme (ACE), and angiotensinogen (AG) expression were also determined. Wistar rats were treated with isoproterenol for 7 days (5 mg x kg(-1) x day(-1) sc). For untreated animals, the levels of tonin-specific activity in the atrium were 2.6- and 5.5-fold higher than those of the left and right ventricle, respectively. After treatment, the levels of tonin-specific activity increased twofold in the atrium but did not change in the ventricles. Renin expression was not detectable in these structures, and ACE expression levels did not change with treatment. AG expression was detected in the left ventricle at very low levels compared with the atrium and increased significantly only in the hypertrophied atrium (1.8-fold). Tonin mRNA was not detected in the ventricle but was found at low levels in the atrium, which increased after isoproterenol treatment. Our results permit us to conclude that tonin may play a role in the process of heart hypertrophy in the rat.
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Affiliation(s)
- Julio Cesar Borges
- Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Brazil.
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Lomez ESL, Araujo RC, Bader M, Pesquero JB, Pesquero JL. Tonin and kallikrein in the brain of transgenic rat line expressing human tissue kallikrein. Hypertension 2002; 39:229-32. [PMID: 11847189 DOI: 10.1161/hy0202.104264] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A transgenic rat line harboring the human tissue kallikrein gene was investigated for expression and activity of tonin and kallikrein in different regions of the brain. The introduction of the transgene into the rat genome produced a significant augmentation of the expression levels and activity of rat tissue kallikrein. The possibility that human kallikrein does not hydrolyze the rat substrate is probably responsible for the augmented expression of the rat enzyme. On the other hand, although expression of tonin was significantly reduced, tonin activity was not altered in most brain structures, except for cerebellum and neurohypophysis.
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Affiliation(s)
- Eliane S L Lomez
- Department of Physiology, Instituto de Ciencias Biologicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
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Hilgers KF, Veelken R, Müller DN, Kohler H, Hartner A, Botkin SR, Stumpf C, Schmieder RE, Gomez RA. Renin uptake by the endothelium mediates vascular angiotensin formation. Hypertension 2001; 38:243-8. [PMID: 11509484 DOI: 10.1161/01.hyp.38.2.243] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We investigated the role of the vascular endothelium in the local production of angiotensin. Angiotensin release from isolated rat hindquarters perfused with an artificial medium was measured by high-performance liquid chromatography and radioimmunoassay. Perfused hindquarters with endothelium released angiotensin I spontaneously, indicating ongoing renin-angiotensinogen reaction. Endothelium denudation (by a detergent, validated by electron microscopy and by the absence of a vasodilator response to acetylcholine) reduced angiotensin I release by >90%, whereas bilateral nephrectomy 24 hours before perfusion abolished the release completely. Infusion of renin into perfused hindquarters induced sustained local angiotensin I release in the presence of an intact endothelium but not after endothelium denudation. The conversion of angiotensin I to angiotensin II was abrogated by endothelium denudation, whereas the disappearance of angiotensin II was unchanged. Endothelium denudation diminished the pressor response to angiotensin II but abolished the response to renin and angiotensin I. Expression of renin messenger RNA, investigated by reverse-transcription polymerase chain reaction using 4 different primer combinations, was not detected in up to 5 microg vascular RNA, whereas a renin signal was readily detected with 5 ng kidney RNA. The effects of endothelium destruction on Ang I formation support the notion that the endothelium mediates vascular angiotensin formation by taking up renin.
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Affiliation(s)
- K F Hilgers
- Department of Medicine-Nephrology, University of Erlangen-Nürnberg, Erlangen, Germany.
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Boddi M, Poggesi L, Coppo M, Zarone N, Sacchi S, Tania C, Neri Serneri GG. Human vascular renin-angiotensin system and its functional changes in relation to different sodium intakes. Hypertension 1998; 31:836-42. [PMID: 9495269 DOI: 10.1161/01.hyp.31.3.836] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A growing body of evidence supports the existence of a tissue-based renin-angiotensin system (RAS) in the vasculature, but the functional capacity of vascular RAS was not investigated in humans. In 28 normotensive healthy control subjects, the metabolism of angiotensins through vascular tissue was investigated in normal, low, and high sodium diets by the measurement of arterial-venous gradient of endogenous angiotensin (Ang) I and Ang II in two different vascular beds (forearm and leg), combined with the study of 125I-Ang I and 125I-Ang II kinetics. In normal sodium diet subjects, forearm vascular tissue extracted 36+/-6% of 125I-Ang I and 30+/-5% of 125I-Ang II and added 14.9+/-5.1 fmol x 100 mL(-1) x min(-1) of de novo formed Ang I and 6.2+/-2.8 fmol x 100 mL(-1) x min(-1) of Ang II to antecubital venous blood. Fractional conversion of 125I-Ang I through forearm vascular tissue was about 12%. Low sodium diet increased (P<.01) plasma renin activity, whereas de novo Ang I and Ang II formation by forearm vascular tissue became undetectable. Angiotensin degradation (33+/-7% for Ang I and 30+/-7% for Ang II) was unchanged, and vascular fractional conversion of 125I-Ang I decreased from 12% to 6% (P<.01). In high sodium diet subjects, plasma renin activity decreased, and de novo Ang I and Ang II formation by forearm vascular tissue increased to 22 and 14 fmol x 100 mL(-1) x min(-1), respectively (P<.01). Angiotensin degradation did not significantly change, whereas fractional conversion of 125I-Ang I increased from 12% to 20% (P<.01). Leg vascular tissue functional activities of RAS paralleled those of forearm vascular tissue both at baseline and during different sodium intake. These results provide consistent evidence for the existence of a functional tissue-based RAS in vascular tissue of humans. The opposite changes of plasma renin activity and vascular angiotensin formation indicate that vascular RAS is independent from but related to circulating RAS.
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Affiliation(s)
- M Boddi
- Istituto di Medica Generale e Cardiologia, University of Florence, Italy
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Yosipiv IV, el-Dahr SS. Activation of angiotensin-generating systems in the developing rat kidney. Hypertension 1996; 27:281-6. [PMID: 8567053 DOI: 10.1161/01.hyp.27.2.281] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The present study was designed to determine the developmental changes in intrarenal angiotensin (Ang) peptides in the rat. Kidney Ang I and II levels were threefold and sixfold higher in newborn than adult kidneys, respectively (Ang I, 678 +/- 180 versus 243 +/- 38 fmol/g, P < .01; Ang II, 667 +/- 75 versus 103 +/- 6 fmol/g, P < .001). Intrarenal Ang II levels correlated positively with the temporal changes in renin gene expression (r = .93, P < .001). However, no correlation was found between renal Ang II content and angiotensin-converting enzyme (ACE) expression during development, which prompted us to evaluate whether renal enzymes, other than renin and ACE, contribute to Ang II formation in the developing kidney. Angiotensin peptide levels were measured in newborn and adult kidney homogenates incubated with human angiotensinogen (a poor rat renin substrate) for 30 minutes at 37 degrees C. Inhibitors of aspartyl proteases and metalloproteases were ineffective in preventing the formation of Ang II in either newborn or adult kidneys. However, addition of the serine protease inhibitors soybean trypsin inhibitor and phenylmethylsulfonyl fluoride inhibited Ang II generation in the newborn kidneys only. In contrast, Ang I generation was not affected by inhibition of serine proteases in either newborn or adult kidneys. We conclude that Ang I and II synthesis is activated in the developing rat kidney. In addition to renin and ACE, the newborn rat kidney expresses serine protease activity that is capable of generating Ang II directly from angiotensinogen. This putative enzyme is induced in the newborn kidney and may cooperate with renin in the activation of Ang II synthesis during early development.
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Affiliation(s)
- I V Yosipiv
- Department of Pediatrics, Tulane University School of Medicine, New Orleans, LA 70112, USA
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Hanssens M, Vercruysse L, Verbist L, Pijnenborg R, Keirse MJ, Van Assche FA. Renin-like immunoreactivity in human placenta and fetal membranes. Histochem Cell Biol 1995; 104:435-42. [PMID: 8777729 DOI: 10.1007/bf01464333] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Five antibodies that stained renin in the kidney were used to investigate the presence of renin in human placenta and fetal membranes. Despite a large number of experimental approaches to enhance penetration of the immunoglobulins, only two of them showed immunostaining in placenta and fetal membranes. Staining was found in placental syncytiotrophoblast, the amnionic epithelium overlying the placenta, and in glandular epithelial cells present in the decidua adhering to the fetal membranes. It was most consistent, however, in a small infiltrating cell type dispersed through the fetoplacental layers. The two antibodies that revealed immunostaining in all preparations showed high affinity cross-reactivity with cathepsin D. Among other, less plausible, explanations, this raises the possibility that the bulk of 'renin' found in placenta and fetal membranes is not identical to renal renin, but may be cathepsin D or a substance related to both cathepsin D and renin.
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Affiliation(s)
- M Hanssens
- Department of Obstetrics and Gynaecology, University of Leuven, Belgium
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Affiliation(s)
- S M Schwartz
- Department of Pathology, University of Washington, Seattle 98195-7335, USA
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12
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Rosenthal J. Role of renal and extrarenal renin-angiotensin system in the mechanism of arterial hypertension and its sequelae. Steroids 1993; 58:566-72. [PMID: 8116011 DOI: 10.1016/0039-128x(93)90097-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The role of the renin-angiotensin system in cardiovascular function and disease has long been recognized. The renin-angiotensin system was originally thought to be only active in the plasma as a circulating endocrine system, controlling blood pressure and electrolyte homeostasis. The recent introduction of new biotechnologies to cardiovascular research has demonstrated that the renin-angiotensin system can operate as both an endocrine (circulating) and an autocrine/paracrine (tissue) system. The endocrine component is involved with acute circulating homeostasis, whereas it is believed that the tissue renin-angiotensin system participates in the tonic regulation of cardiovascular function and structure. Multiple lines of evidence support the presence of complete renin-angiotensin systems in the central nervous system, vasculature, adrenal, heart, kidney, and reproductive organs. Although more research is necessary to delineate the role of tissue renin-angiotensin systems in local tissue function, the significant contribution of the renin-angiotensin system in the pathophysiology of cardiovascular disease is increasingly apparent (Table 1).
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Affiliation(s)
- J Rosenthal
- Section Pharmacotherapy, Ulm University Medical Center, Germany
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Duntas L, Keck FS, Haug C, Hetzel W, Wolf CF, Rosenthal J, Pfeiffer EF. Serum angiotensin-converting enzyme activity and active renin plasma concentrations in insulin-dependent diabetes mellitus. Diabetes Res Clin Pract 1992; 16:203-8. [PMID: 1330463 DOI: 10.1016/0168-8227(92)90118-b] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We report here the alterations of serum angiotensin-converting enzyme activity (S-ACE) and of active renin plasma concentrations (ARPC) in 41 insulin-dependent diabetes mellitus (IDDM) patients compared with those of 26 control subjects. The IDDM patients had S-ACE activity (54 +/- 16 I.E.) in the upper normal range (controls, 39 +/- 7). When the patients were subclassified according to their diabetic complications, a significant increase of S-ACE within the IDDM group compared to the controls was observed in patients with nephropathy (68 +/- 13, P less than 0.001) with persistent proteinuria and with retinopathy (63 +/- 14, P less than 0.001). A significant correlation was found between proteinuria and S-ACE (r = 0.98, P less than 0.001) and between retinopathy and S-ACE levels (r = 64, P less than 0.001). No correlation between blood pressure and S-ACE or between blood glucose and S-ACE was observed. The ARPC were within the normal range in the IDDM (21 +/- 9 ng/l) and in control (19 +/- 3) groups. No correlations between ARPC and blood pressure or blood glucose or the degree of diabetic complications were registered. These data show that S-ACE activity is elevated in IDDM patients with nephropathy-proteinuria and/or with retinopathy and the circulating renin may not represent the renal renin-angiotensin vascular system.
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Affiliation(s)
- L Duntas
- Department of Internal Medicine I, University of Ulm, Germany
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Abstract
Over the past 25 years, the concept of circulation in heart failure has evolved from that of a simple circuit with a weak pump and high pressures to a complex integrated system of cellular modification, cardiac compensation and systemic neurohumoral responses. The original model of cardiac afterload as the systemic vascular resistance has been refined to reflect the interdependence of preload and afterload and the central role of atrioventricular valve regurgitation. It is becoming increasingly apparent that the impact of vasodilator therapy far exceeds the direct haemodynamic effects on preload and afterload, and depends on the mechanism by which vasodilation is achieved, with increasing emphasis on those agents which oppose neurohumoral activation. The potential goals of therapy have broadened to include not only haemodynamic stabilisation through tailored therapy for patients referred with advanced heart failure, but also the prevention of disease progression for patients with asymptomatic ventricular dilation. As the different profiles of heart failure have come to be recognised, the purpose and design of vasodilator treatment must now be considered individually for each patient.
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Affiliation(s)
- L W Stevenson
- Ahmanson-UCLA Cardiomyopathy Center, School of Medicine, University of California, Los Angeles
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Baxter JD, Duncan K, Chu W, James MN, Russell RB, Haidar MA, DeNoto FM, Hsueh W, Reudelhuber TL. Molecular biology of human renin and its gene. RECENT PROGRESS IN HORMONE RESEARCH 1991; 47:211-57; discussion 257-8. [PMID: 1745821 DOI: 10.1016/b978-0-12-571147-0.50011-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
This article describes investigations of several aspects of the molecular biology of the human renin gene and the three-dimensional structure of renin and its precursor, prorenin. Because of the importance of the RAS in hypertension, heart failure, renal failure, and possibly other disorders such as atherosclerosis, it is critical to understand the detailed control of this system. This control involves regulation at the transcriptional level, folding of prorenin, sorting of prorenin to a regulated pathway where it is proteolytically cleaved to renin and released in response to secretogogues, constitutive release of uncleaved prorenin, and nonproteolytic activation of prorenin. Currently there is great interest not only in the control of renin in the kidney, the sole source of circulating renin, but also at extrarenal sites where RAS activity may regulate cardiovascular functions. The renin gene was found to be expressed significantly in the renal juxtaglomerular cells and several other cell types. Most tissue culture cells did not express the gene; exceptions were cultured SK-LMS-1 cells and cAMP-stimulated human lung fibroblasts. Cultured human uterine-placental cells expressed the human renin gene at levels higher than in other cell types assessed. Renin mRNA had the same start site in the placental cells as the kidney and was regulated by calcium ionophores and cAMP. Thus, these cells provide primary nontransformed human cells to study the homologous human promoter. Transfected renin promoters showed cell type-specific expression and cAMP responsiveness in these cells in constructs containing as few as 102 bp of 5'-flanking DNA. DNA upstream from this appears to contain an inhibitory element(s) that may have some tissue specificity in its distribution. The cAMP response is not due to cAMP induction of a transcription factor that secondarily affects the renin promoter. A novel element may be involved, since the promoter does not contain a CRE element that mediates many cAMP responses, and the cells do not appear to respond to another known cAMP-responsive transcription factor, AP-2. Studies with transfected vectors expressing a mutant cAMP-responsive protein kinase A regulatory subunit suggest that cAMP is not responsible for basal renin promoter activity in the placental cells. By contrast, cAMP induces in essence gene activation in WI26VA4 transformed human lung fibroblasts in which renin mRNA levels increase by up to 150-fold in response to forskolin. Thus, cAMP may activate renin gene expression under certain circumstances and tissue-specific renin gene expression may be directed by more than one mechanism.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- J D Baxter
- Metabolic Research Unit, University of California, San Francisco
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