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      Role of Renal Nitric Oxide Synthase in Diabetic Kidney Disease during the Chronic Phase of Diabetes

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          Abstract

          Background: Several studies have suggested that an early increase in renal nitric oxide (NO) production or activity mediates pathophysiologic and morphologic changes in diabetic nephropathy. To evaluate the role of NO in developing diabetic kidney disease, we studied the NO system in streptozotocin (STZ)-induced diabetic rats for a period of 8 weeks. Methods: Control rats, STZ-induced diabetic rats, and STZ-induced diabetic rats treated with insulin were monitored and sacrificed at 1, 2, and 8 weeks. Urinary cGMP was measured, and the levels and activity of NO synthase (NOS) isoforms in the kidney cortex were determined at specific times by immunoblotting and diaphorase staining. Results: Diabetic rats had increased kidney weight, urinary volume, glucose, sodium and potassium excretion, which was precluded by insulin treatment. Creatinine clearance was increased in the diabetic group and reversed by insulin treatment. Urinary cGMP decreased by 71, 93, and 92% at 1, 2, and 8 weeks of diabetes, respectively, compared with the control animals. Insulin treatment curtailed the urinary cGMP reduction in diabetic animals. Total NOS activity in the renal cortex was reduced by 65, 52, and 44% after 1, 2, and 8 weeks of diabetes, respectively, and returned to normal levels upon insulin treatment. NADPH diaphorase staining of renal cortical slices showed a 77, 63, and 70% decrease in neuronal NOS isoform activity in the macula densa after 1, 2, and 8 weeks of diabetes, respectively, compared with control non-diabetic animals. This reduction was normalized by insulin treatment. Endothelial NOS protein expression in the kidney cortex tended to increase after 1 week of diabetes and its level was elevated significantly after 2 and 8 weeks of diabetes. However, neuronal NOS protein expression in the kidney cortex was reduced by 52% in 2-week diabetic animals, but this reduction was normalized by insulin treatment. Conclusions: The decreased renal NOS activity during the late phase of diabetes is partially associated with a decrease in neuronal NOS activity and protein expression in kidney macula densa.

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          Most cited references 19

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          Advanced glycation end products-cytokine-nitric oxide sequence pathway in the development of diabetic nephropathy: aminoguanidine ameliorates the overexpression of tumour necrosis factor-alpha and inducible nitric oxide synthase in diabetic rat glomeruli.

          Advanced glycation end products are believed to contribute to diabetic microvascular complications by inducing glomerular damage but their role has not been fully clarified. In this study, we explain their central role in the induction of inducible nitric oxide synthase and production of nitric oxide (NO) in streptozotocin-induced diabetic rat glomeruli. Localization of carboxymethyllysine, which is one of the chemical components of advanced glycation end products, glomerular expression of inducible nitric oxide synthase and urinary excretion and glomerular production of NO2-/NO3- were examined at 0, 26, 51, and 52 weeks after the induction of diabetes. Therapeutic effects of aminoguanidine were also examined. Carboxymethyllysine was detected in the mesangial area in glomeruli and it progressively accumulated during 52 weeks of observation. Immunohistochemistry and hybridization studies in situ showed that the number of inducible nitric oxide synthase-positive cells was notably increased in diabetic rat glomeruli at 52 weeks. Further, this augmented expression paralleled intraglomerular expression of TNF-alpha and NO2-/NO3- in diabetic rat glomeruli. Treatment with aminoguanidine reduced the expression of TNF-alpha, inducible nitric oxide synthase and intraglomerular NO2-/NO3- production. It also ameliorated proteinuria in diabetic rats. This study showed that carboxymethyllysine possibly enhances the expression of inducible nitric oxide synthase by stimulating the expression of TNF-alpha in diabetic rat glomeruli. The carboxymethyllysine-cytokine-NO sequence pathway could be one of the major mechanisms in the development of diabetic nephropathy.
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            Laparoscopic repair of wide and deep uterine scar dehiscence after cesarean section.

            To propose a new laparoscopic technique for repair of scar dehiscence after cesarean section. The dehiscent scars were evaluated by ultrasound, hysterography, hysteroscopy, and magnetic resonance imaging. The results were correlated with those after laparoscopic repair. University hospital. Three patients underwent cesarean section and presented with symptomatic dehiscence at the level of the incision. Laparoscopic repair of the dehiscence, including excision of the fibrotic tissue and laparoscopic closure of the anterior uterine wall. Evaluation by ultrasound and magnetic resonance imaging of the sagittal depth of the scar and the thickness of the residual myometrium covering the dehiscence. The defect was completely corrected by laparoscopic repair in all cases. Evaluation of uterine scar dehiscence after cesarean section can be performed by ultrasound and magnetic resonance imaging, and laparoscopic surgical repair may be performed with good postoperative anatomic outcomes.
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              Increased expression of endothelial cell nitric oxide synthase (ecNOS) in afferent and glomerular endothelial cells is involved in glomerular hyperfiltration of diabetic nephropathy.

              The overproduction of nitric oxide (NO) is reported in the diabetic kidney and considered to be involved in glomerular hyperfiltration. The precise mechanism of NO production in the diabetic kidney is, however, not known. In this report, we compare the localization of endothelial cell nitric oxide synthase (ecNOS) isoform expression in the kidney tissue of streptozotocin (STZ)-induced diabetic rats and 5/6 nephrectomized rats and clarify the pivotal role of ecNOS for the glomerular hyperfiltration in the early stages of diabetic nephropathy. In diabetic rats, the diameters of afferent arterioles, the glomerular volume, creatinine clearance, and urinary NO2/NO3 were increased after the induction of diabetes. Efferent arterioles were, however, not altered. Insulin or L-NAME treatment returned the diameters of afferent arterioles, glomerular volume, creatinine clearance, and urinary NO2/NO3 to normal. The expression of ecNOS in afferent arterioles and glomeruli of diabetic rats increased during the early stages of the disease, but was not altered in efferent arterioles. Treatment with either insulin or L-NAME decreased ecNOS expression in afferent arterioles and in glomeruli. In contrast, the ecNOS expression was upregulated in both afferent and efferent arterioles and in the glomeruli of 5/6 nephrectomized rats, where the dilatation of afferent and efferent arterioles and glomerular enlargement were observed. Treatment with L-NAME ameliorated the ecNOS expression and dilatation of arterioles. We conclude that enhanced NO synthesis by ecNOS in afferent arterioles and glomerular endothelial cells in response to the hyperglycaemic state could cause preferential dilatation of afferent arterioles, which ultimately induces glomerular enlargement and glomerular hyperfiltration.
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                Author and article information

                Journal
                NEP
                Nephron Physiol
                10.1159/issn.1660-2137
                Nephron Physiology
                S. Karger AG
                1660-2137
                2006
                February 2006
                23 February 2006
                : 102
                : 3-4
                : p72-p80
                Affiliations
                a Department of Internal Medicine B and the Diabetes Center, and b Department of Neurology, Hadassah University Hospital, Jerusalem, Israel
                Article
                89946 Nephron Physiol 2006;102:p72–p80
                10.1159/000089946
                16319502
                © 2006 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: 5, Tables: 2, References: 37, Pages: 1
                Product
                Self URI (application/pdf): https://www.karger.com/Article/Pdf/89946
                Categories
                Original Paper

                Cardiovascular Medicine, Nephrology

                Cortex, Macula densa, Nitric oxide synthase, neuronal

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