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      Increased Plasma Levels of Mature Adrenomedullin in Chronic Glomerulonephritis

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          Abstract

          Adrenomedullin (AM) is a potent vasodilative and natriuretic peptide that is processed from its precursor as the intermediate form, AM-glycine-COOH (iAM). Subsequently, iAM is converted to the biologically active mature form, AM(1-52)-CONH<sub>2</sub> (mAM), by enzymatic amidation. Using immunoradiometric assays that recognize total AM (tAM) and only mAM, we determined the plasma and urinary levels of mAM and iAM in patients with chronic glomerulonephritis (CGN). The plasma mAM concentration was significantly higher in the patients than in the controls (1.8 ± 0.1 vs. 1.3 ± 0.1 fmol/ml, p < 0.01), whereas the plasma iAM concentration of the CGN patients did not significantly differ from that of the controls (9.4 ± 0.5 vs. 8.9 ± 0.5 fmol/ml). Levels of urinary mAM excretion in the patients did not statistically differ from those of the controls (1.6 ± 0.4 vs. 2.0 ± 0.3 fmol/mg creatinine), whereas urinary iAM excretion was significantly lower in the CGN patients (3.7 ± 0.7 vs. 5.6 ± 0.8 fmol/mg creatinine, p < 0.05). Urinary excretion levels of mAM significantly correlated with those of sodium (r = 0.47, p < 0.05), whereas those of iAM did not. In conclusion, the plasma ratio of mAM to iAM is augmented in CGN patients, and mAM appears to be involved in the regulation of sodium. Therefore, determination of the mAM in addition to the tAM concentration is essential in CGN patients.

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          Most cited references 8

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          Endothelial cells actively synthesize and secrete adrenomedullin.

          This study demonstrates active production of adrenomedullin (AM) in cultured vascular endothelial cells (ECs). To identify the origin of plasma AM and its functional relationship to vascular smooth muscle cells (VSMCs), we checked production of AM in a series of tissues and cell lines and found immunoreactive (ir-) AM in culture media of rat, porcine, human and bovine ECs. Ir-AM was accumulated linearly for up to 48 hours in the culture medium of rat ECs, and the secretion rate of AM was almost comparable to that of endothelin-1. By gel filtration and reverse phase high performance liquid chromatography, ir-AM in the culture medium was shown to have chromatographic behavior indistinguishable from that of synthetic rat AM. By RNA blot analysis of rat tissue, the most highly positive band was detected in cultured ECs, at an intensity 20 to 40 fold higher than that in adrenal gland. Based on these data as well as the presence of AM specific receptor on VSMCs, AM secreted from ECs is deduced to act directly on VSMCs, regulating vascular tone.
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            Cloning and characterization of cDNA encoding a precursor for human adrenomedullin.

            Adrenomedullin is a novel hypotensive peptide recently isolated from human pheochromocytoma. Since a high concentration of immunoreactive adrenomedullin was found in pheochromocytoma tissue, the cDNA library of pheochromocytoma was constructed, and the cDNA clone encoding an adrenomedullin precursor was isolated and sequenced. The precursor for human adrenomedullin (human preproadrenomedullin) is 185 amino acids in length, including an adrenomedullin sequence. Proadrenomedullin (proAM) contains a unique twenty amino acid sequence followed by Gly-Lys-Arg in the N-terminal region. It is possible that a novel 20 residues peptide, termed "proadrenomedullin N-terminal 20 peptide" (proAM-N20) whose carboxy terminus may be Arg-NH2, is processed from proadrenomedullin. By RNA blot analysis, human adrenomedullin mRNA was found to be highly expressed in several tissues including adrenal medulla, ventricle, lung and kidney as well as pheochromocytoma.
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              Interleukin-1, tumor necrosis factor and lipopolysaccharide additively stimulate production of adrenomedullin in vascular smooth muscle cells.

              To elucidate physiological functions of adrenomedullin (AM) secreted from vascular smooth muscle cells (VSMCs), we examined the effect of cytokines, growth factors and related substances on AM production in cultured rat VSMC. Among them, interleukin-1 alpha (IL-1 alpha), IL-1 beta, tumor necrosis factor-alpha (TNF-alpha) and TNF-beta, as well as lipopolysaccharide (LPS), markedly augmented production and gene expression of AM. Although maximal stimulation levels of these substances were not greatly different, ED50 values of IL-1s (0.3 ng/ml) were about 1/10 that of TNFs and LPS. AM mRNA levels maximized at 3-6 h after stimulation with IL-1 beta and LPS, while TNF-alpha increased the AM mRNA level up to 48 h. Furthermore, IL-1 alpha, TNF-alpha and LPS additively increased AM production in VSMC. AM production was slightly augmented by fibroblast, epidermal and platelet derived growth factors. These results suggest that AM secreted from VSMC actually exerts a vasorelaxant effect under physiological conditions such as endotoxin shock, atherosclerosis and inflammation.
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                Author and article information

                Journal
                NEF
                Nephron
                10.1159/issn.1660-8151
                Nephron
                S. Karger AG
                1660-8151
                2235-3186
                2000
                November 2000
                08 November 2000
                : 86
                : 3
                : 333-338
                Affiliations
                First Department of Internal Medicine, Miyazaki Medical College, Miyazaki, Japan
                Article
                45789 Nephron 2000;86:333–338
                10.1159/000045789
                11096291
                © 2000 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                Figures: 3, Tables: 1, References: 27, Pages: 6
                Product
                Self URI (application/pdf): https://www.karger.com/Article/Pdf/45789
                Categories
                Short Communication

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