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      The Roles of Intrarenal 20-Hydroxyeicosatetraenoic and Epoxyeicosatrienoic Acids in the Regulation of Renal Function in Hypertensive Ren-2 Transgenic Rats

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          Background: The present study was performed in hypertensive Ren-2 transgenic rats (TGR) and in normotensive Hannover Sprague-Dawley (HanSD) rats. First, the intrarenal protein expression of CYP4A, the enzyme catalyzing the formation of 20-hydroxyeicosatetraenoic acid (20-HETE), and of CYP2C23, the enzyme responsible for epoxyeicosatrienoic acid (EET) production, was evaluated. Second, the renal functional responses to inhibition of the intrarenal formation of 20-HETE and EETs were investigated. Methods: Renal hemodynamics and electrolyte excretion were evaluated in response to the administration of inhibitors of 20-HETE and EET formation into the renal artery. In renal cortical tissue, CYP4A and CYP2C23 protein expression was assessed by Western blot analysis. Urinary concentrations of 20-HETE and EETs were measured using a fluorescent HPLC assay. Results: TGR have higher kidney CYP4A protein expression and urinary 20-HETE excretion but significantly lower CYP2C23 protein expression and urinary EET excretion than HanSD. Intrarenal inhibition of 20-HETE and EET formation decreased sodium excretion in HanSD, whereas inhibition of 20-HETE increased urinary excretion of sodium in TGR without altering renal hemodynamics. Conclusions: Our data suggest that in TGR, deficient intrarenal synthesis of EETs combined with increased synthesis of 20-HETE with its stimulation of tubular sodium absorption may contribute to the development of hypertension in TGR.

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          Most cited references 26

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          Epoxide hydrolase and epoxygenase metabolites as therapeutic targets for renal diseases.

           John D. Imig (2005)
          Renal epoxygenase metabolites are involved in blood flow regulation and long-term blood pressure control. One feature of renal and cardiovascular diseases is the inability of the kidney to properly increase epoxyeicosatrienoic acid (EET) levels. Others (Busse R, Edwards G, Félétou M, Fleming I, Vanhoutte PM, and Weston AH. Trends Phamacol Sci 23: 374-380, 2002; Campbell WB, Gebremedhin D, Pratt PF, and Harder DR. Circ Res 78: 415-423, 1996; Capdevila JH and Falck JR. Biochem Biophys Res Commun 285: 571-576, 2001; Roman RJ. Physiol Rev 82: 131-185, 2002; Zeldin DC. J Biol Chem 276: 36059-36062, 2001) and we (Imig JD, Falck JR, Wei S, and Capdevila JH. J Vasc Res 38: 247-255, 2001; Imig JD, Zhao X, Capdevila JH, Morisseau C, and Hammock BD. Hypertension 39: 690-694, 2002; Zhao X, Pollock DM, Inscho EW, Zeldin DC, and Imig JD. Hypertension 41: 709-714, 2003; Zhao X, Pollock DM, Zeldin DC, and Imig JD. Hypertension 42: 775-780, 2003) have provided compelling evidence that cytochrome P-450-derived EETs have antihypertensive properties and are endothelially derived hyperpolarizing factors (EDHFs) in the kidney. EETs also possess anti-inflammatory actions that could protect the kidney vasculature from injury during renal and cardiovascular diseases. A tactic that has been used to increase EET levels has been inhibition of the soluble epoxide hydrolase enzyme. Epoxide hydrolase inhibitors have been demonstrated to be antihypertensive and renal protective. Thus the renal and cardiovascular protective actions of increasing epoxygenase levels could be translated to therapies for preventing end-organ damage.
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            An orally active epoxide hydrolase inhibitor lowers blood pressure and provides renal protection in salt-sensitive hypertension.

            The present study tested the hypothesis that increasing epoxyeicosatrienoic acids by inhibition of soluble epoxide hydrolase (sEH) would lower blood pressure and ameliorate renal damage in salt-sensitive hypertension. Rats were infused with angiotensin and fed a normal-salt diet or an 8% NaCl diet for 14 days. The sEH inhibitor, 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA), was given orally to angiotensin-infused animals during the 14-day period. Plasma AUDA metabolite levels were measured, and they averaged 10+/-2 ng/mL in normal-salt angiotensin hypertension and 19+/-3 ng/mL in high-salt angiotensin hypertension on day 14 in the animals administered the sEH inhibitor. Mean arterial blood pressure averaged 161+/-4 mm Hg in normal-salt and 172+/-5 mm Hg in the high-salt angiotensin hypertension groups on day 14. EH inhibitor treatment significantly lowered blood pressure to 140+/-5 mm Hg in the normal-salt angiotensin hypertension group and to 151+/-6 mm Hg in the high-salt angiotensin hypertension group on day 14. The lower arterial blood pressures in the AUDA-treated groups were associated with increased urinary epoxide-to-diol ratios. Urinary microalbumin levels were measured, and ED-1 staining was used to determine renal damage and macrophage infiltration in the groups. Two weeks of AUDA treatment decreased urinary microalbumin excretion in the normal-salt and high-salt angiotensin hypertension groups and macrophage number in the high-salt angiotensin hypertension group. These data demonstrate that sEH inhibition lowers blood pressure and ameliorates renal damage in angiotensin-dependent, salt-sensitive hypertension.
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              Urinary Angiotensinogen as an Indicator of Intrarenal Angiotensin Status in Hypertension


                Author and article information

                Kidney Blood Press Res
                Kidney and Blood Pressure Research
                S. Karger AG
                September 2007
                30 August 2007
                : 30
                : 5
                : 335-346
                aCenter for Experimental Medicine, Institute for Clinical and Experimental Medicine, and bDepartment of Nephrology, First Medical Faculty, and cDepartment of Physiology, Second Medical Faculty, Charles University, and dCenter for Cardiovascular Research, Prague, Czech Republic; eSection of Nephrology, Medical Policlinic, Department of Medicine, University of Bonn, Bonn, Germany; fDepartment of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Tex., and gDepartment of Physiology, Vascular Biology Center, Medical College of Georgia, Augusta, Ga., USA
                107710 Kidney Blood Press Res 2007;30:335–346
                © 2007 S. Karger AG, Basel

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                Page count
                Figures: 7, Tables: 1, References: 61, Pages: 12
                Original Paper


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