锘縤nduced adrenomedullin production in the kidney Daisuke Nagata, [url=http://www.ideatrade.it/abercrombiemilano/]abercrombie milano sito ufficiale[/url] Yasunobu Hirata, Etsu Suzuki, Masao Kakoki, Hiroshi Hayakawa, Atsuo Goto, Toshihiko Ishimitsu, Naoto Minamino, Yukari Ono, Kenji Kangawa, Hisayuki Matsuo and Masao OmataReceived 16 April 1998; Revised 30 October 1998; Accepted 30 October 1998.Top of pageAbstract.Background Adrenomedullin (AM) is a newly discovered peptide prada outlet onlinethat has a potent vasorelaxant activity. To investigate its potential roles in hypoxiainduced renal injury, we examined whether AM production in the kidney increased under hypoxic conditions.Methods The AM transcript levels in MadinDarby canine kidney (MDCK) cells, rat vascular smooth muscle cells (VSMCs), and rat mesangial woolrich outletcells were assessed by Northern blot analyses under normoxic and hypoxic conditions. The AM peptide in culture media was measured by radioimmunoassay. The effects of hypoxia on accumulation of cAMP in VSMCs were also examined. The stability of AM transcripts under normoxic and hypoxic conditions was compared in the presence of actinomycin D. The effects of hypoxia on AM promoter activity was assessed by longchamps bag uk transient transfection assays using the AM promoter subcloned upstream of luciferase gene.Results The expression of AM transcripts increased significantly in MDCK cells, rat VSMCs, and rat mesangial cells under hypoxic conditions without changes in the stability of AM transcripts; however, the AM promoter activity under hypoxia was not elevated significantly. The accumulation of AM peptide in culture media also increased significantly under hypoxic conditions in MDCK cells (2.2 0.1 fmol/105 cells in normoxia vs. 3.5 0.3 fmol/105 cells in hypoxia, 6 hr after hypoxia induction, P 0.3 fmol/105 cells in normoxia vs. 7.8 0.4 fmol/105 cells in hypoxia, 8 hr after hypoxia induction, P 1.4 pmol/well vs. 4.6 0.4 pmol/well, PConclusions Renal parenchymal cells as well as renal vessels may produce AM under hypoxic conditions.Keywords: MDCK cells, vascular smooth muscle, vasorelaxant, renal injury, acute tubular necrosisThe kidney is one of the organs that is most sensitive to hypoxia. Hypoxia damages renal tubules, especially those located in the outer medulla, resulting in pathophysiological states such as acute tubular necrosis. Although the precise mechanisms of renal functions impairment under hypoxic conditions remain to be elucidated, one of them might be a prolonged intrarenal vasoconstriction, which predominantly damages renal tubules located in the outer medulla. Recent studies indicate that sustained vasoconstriction can be attributed to increased endothelin1 (ET1) production1 and decreased nitric oxide (NO) production2, suggesting that other vasoactive substances may also participate in the modulation of the tone of renal vessels.Recently, adrenomedullin (AM) was isolated from human pheochromocytoma tissue. Adrenomedullin comprises 52 amino acids and shows slight homology with the calcitonin generelated peptide (CGRP)3. Although AM was originally isolated from pheochromocytoma tissue, it is distributed broadly in a variety of tissues, including the kidney3,4,5. Several immunohistochemical studies and in situ hybridization studies have demonstrated that AM is produced in the renal [url=http://www.dtdrivingschool.co.uk/giuseppezanotti/]giuseppe zanotti sneakers gold buckle[/url] cortex, including the glomeruli and renal tubules. Furthermore, AM is now known to be present in vascular smooth muscle cells (VSMCs)4 and endothelial cells6, suggesting that renal vessels as well as renal tubules and glomeruli are the source of AM production in the kidney. We have previously reported that AM has potent renal vasorelaxant and natriuretic effects in the rat, which appear to be mediated, at least in part, by increased NO production in the kidney7. Several reports have suggested that AM also has potent vasodilator and natriuretic actions that seem to be mediated by NOcGMP pathways, although the degree of involvement of NOcGMP pathways in AMinduced vasodilation depends on the species studied8,9,10. Furthermore, a recent report suggests that AM inhibits plateletderived growth factorinduced and thrombininduced ET1 production in VSMCs11. Thus, it is tempting to speculate that AM may reduce hypoxiainduced renal damage by counteracting with vasoconstricting substances such as ET1 and by increasing NO production in the kidney. To test this hypothesis, we examined whether renal vessels and renal tubular cells, which appear to be the major source of AM production in the kidney, produced AM under hypoxic conditions using MadinDarby canine kidney cells, a cell line derived from canine renal tubular cells, and
