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Montanari A, Lazzeroni D, Pelà G, Crocamo A, Lytvyn Y, Musiari L, Cabassi A, Cherney DZI. Calcium channel blockade blunts the renal effects of acute nitric oxide synthase inhibition in healthy humans. Am J Physiol Renal Physiol 2017; 312:F870-F878. [DOI: 10.1152/ajprenal.00568.2016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Revised: 02/01/2017] [Accepted: 02/06/2017] [Indexed: 01/25/2023] Open
Abstract
Our aim was to investigate whether blockade of calcium channels (CCs) or angiotensin II type 1 receptors (AT1R) modulates renal responses to nitric oxide synthesis inhibition (NOSI) in humans. Fourteen sodium-replete, healthy volunteers underwent 90-min infusions of 3.0 μg·kg−1·min−1 NG-nitro-l-arginine methyl ester (l-NAME) on 3 occasions, preceded by 3 days of either placebo (PL), 10 mg of manidipine (MANI), or 50 mg of losartan (LOS). At each phase, mean arterial pressure (MAP), glomerular filtration rate (GFR; inulin), renal blood flow (RBF; p-aminohippurate), urinary sodium (UNaV), and 8-isoprostane (U8-iso-PGF2αV; an oxidative stress marker) were measured. With PL + l -NAME, the following changes were observed: +6% MAP ( P < 0.005 vs. baseline), −10% GFR, −20% RBF, −49% UNaV ( P < 0.001), and +120% U8-iso-PGF2αV ( P < 0.01). In contrast, MAP did not increase during LOS + l-NAME or MANI + l-NAME ( P > 0.05 vs. baseline), whereas renal changes were the same during LOS + l-NAME vs. PL + l-NAME (ANOVA, P > 0.05). However, during MANI + l-NAME, changes vs. baseline in GFR (−6%), RBF (−12%), and UNaV (−34%) were blunted vs. PL + l-NAME and LOS + l-NAME ( P < 0.005), and the rise in U8-iso-PGF2αV was almost abolished (+37%, P > 0.05 vs. baseline; P < 0.01 vs. PL + l-NAME or LOS + l-NAME). We conclude that, since MANI blunted l-NAME-induced renal hemodynamic changes, CCs participate in the renal responses to NOSI in healthy, sodium-replete humans independent of changes in MAP and without the apparent contribution of the AT1R. Because the rise in U8-iso-PGF2αV was essentially prevented during MANI + l-NAME, CC blockade may oppose the renal effects of NOSI in part by counteracting oxidative stress responses to acutely impaired renal NO bioavailability.
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Affiliation(s)
- Alberto Montanari
- Department of Clinical and Experimental Medicine, University of Parma Medical School, Parma, Italy
| | - Davide Lazzeroni
- Prevention and Rehabilitation Unit at the Don Gnocchi Foundation and Department of Clinical and Experimental Medicine, University of Parma Medical School, Parma, Italy; and
| | - Giovanna Pelà
- Department of Clinical and Experimental Medicine, University of Parma Medical School, Parma, Italy
| | - Antonio Crocamo
- Department of Clinical and Experimental Medicine, University of Parma Medical School, Parma, Italy
| | - Yuliya Lytvyn
- Division of Nephrology, University Health Network, University of Toronto, Toronto, Ontario, Canada
| | - Luisa Musiari
- Department of Clinical and Experimental Medicine, University of Parma Medical School, Parma, Italy
| | - Aderville Cabassi
- Department of Clinical and Experimental Medicine, University of Parma Medical School, Parma, Italy
| | - David Z. I. Cherney
- Division of Nephrology, University Health Network, University of Toronto, Toronto, Ontario, Canada
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Ott C, Raff U, Schneider MP, Titze SI, Schmieder RE. 25-hydroxyvitamin D insufficiency is associated with impaired renal endothelial function and both are improved with rosuvastatin treatment. Clin Res Cardiol 2012; 102:299-304. [PMID: 23262496 DOI: 10.1007/s00392-012-0534-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Accepted: 12/11/2012] [Indexed: 12/11/2022]
Abstract
BACKGROUND Vitamin D deficiency is nowadays considered as a potential cardiovascular and renal risk factor. We tested the hypotheses that vitamin D deficiency impairs the endothelial function of renal vasculature and whether vitamin D levels and endothelial function can be improved by the treatment with statins. METHODS In a double-blind, randomized study of 31 hypercholesterolemic patients with vitamin D insufficiency (<30 ng/ml) were randomly assigned to rosuvastatin (10 mg/d) and placebo for 6 weeks. Basal nitric oxide (NO) activity of the renal vasculature was assessed both before and after the blockade of NO synthases with systemic infusion of N(G)-monomethyl-L-arginine (L-NMMA). In parallel, 25(OH)D was measured. RESULTS Multiple regression analysis revealed that at baseline 25(OH)D is an independent determinant of basal NO activity as assessed by the decrease in RPF, in response to L-NMMA (β = -0.446, r = 0.015). Compared to placebo treatment, rosuvastatin increased 25(OH)D levels (21.6 ± 4.0 vs. 24.1 ± 8.1 ng/ml, p = 0.039). Basal NO activity was significantly more increased after 6-week therapy with rosuvastatin than with placebo (-94.8 ± 70 vs. -68.2 ± 32 ml/min, p = 0.044), indicating increased basal NOS activity after 6 weeks of rosuvastatin treatment. Basal NO activity in the placebo phase was correlated inversely with 25(OH)D (r = -0.385; p = 0.027). CONCLUSIONS Thus, vitamin D insufficiency is associated with impaired endothelial function in the renal vasculature and both were beneficially influenced by the treatment with rosuvastatin.
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Affiliation(s)
- Christian Ott
- Department of Nephrology and Hypertension, University of Erlangen-Nuremberg, Ulmenweg 18, 91054 Erlangen, Germany
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Gamboa A, Okamoto LE, Diedrich A, Choi L, Robertson D, Farley G, Paranjape S, Biaggioni I. Sympathetic activation and nitric oxide function in early hypertension. Am J Physiol Heart Circ Physiol 2012; 302:H1438-43. [PMID: 22287587 DOI: 10.1152/ajpheart.01020.2011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of this study was to determine if tonic restrain of blood pressure by nitric oxide (NO) is impaired early in the development of hypertension. Impaired NO function is thought to contribute to hypertension, but it is not clear if this is explained by direct effects of NO on vascular tone or indirect modulation of sympathetic activity. We determined the blood pressure effect of NO synthase inhibition with N(ω)-monomethyl-l-arginine (L-NMMA) during autonomic blockade with trimethaphan to eliminate baroreflex buffering and NO modulation of autonomic tone. In this setting, impaired NO modulation of vascular tone would be reflected as a blunted pressor response to L-NMMA. We enrolled a total of 66 subjects (39 ± 1.3 yr old, 30 females), 20 normotensives, 20 prehypertensives (blood pressure between 120/80 and 140/90 mmHg), 17 hypertensives, and 9 smokers (included as "positive" controls of impaired NO function). Trimethaphan normalized blood pressure in hypertensives, suggesting increased sympathetic tone contributing to hypertension. In contrast, L-NMMA produced similar increases in systolic blood pressure in normal, prehypertensive, and hypertensive subjects (31 ± 2, 32 ± 2, and 30 ± 3 mmHg, respectively), whereas the response of smokers was blunted (16 ± 5 mmHg, P = 0.012). Our results suggest that sympathetic activity plays a role in hypertension. NO tonically restrains blood pressure by ∼30 mmHg, but we found no evidence of impaired modulation by NO of vascular tone contributing to the early development of hypertension. If NO deficiency contributes to hypertension, it is likely to be through its modulation of the autonomic nervous system, which was excluded in this study.
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Affiliation(s)
- Alfredo Gamboa
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University, Nashville, Tennessee, USA.
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Gjørup PH, Wessels J, Pedersen EB. Abnormally increased nitric oxide synthesis and increased endothelin‐1 in plasma in patients with obstructive sleep apnoea. Scand J Clin Lab Invest 2009; 68:375-85. [DOI: 10.1080/00365510701782382] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Ott C, Schlaich MP, Schmidt BMW, Titze SI, Schäufele T, Schmieder RE. Rosuvastatin improves basal nitric oxide activity of the renal vasculature in patients with hypercholesterolemia. Atherosclerosis 2008; 196:704-11. [PMID: 17298834 DOI: 10.1016/j.atherosclerosis.2006.12.020] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2006] [Revised: 12/19/2006] [Accepted: 12/21/2006] [Indexed: 10/23/2022]
Abstract
OBJECTIVE Impaired endothelium-dependent vasodilation represents an early manifestation of atherosclerosis. Prospective studies have demonstrated that impaired endothelial function in the peripheral circulation of hypercholesterolemic patients predicts CV events and can be restored by statin treatment. Whether this also holds true in the renal circulation has not yet been adequately addressed. METHODS In a double-blind, randomized, placebo-controlled cross-over trial, 40 hypercholesterolemic patients were randomly assigned to receive rosuvastatin (10mg/day) and matching placebo. The primary objective of the study was to assess the effect of 6-week treatment with rosuvastatin on basal NOS activity of the renal vasculature, as assessed by measuring renal plasma flow (RPF) both before and after blockade of NOS with systemic infusion of N(G)-monomethyl-L-arginine (L-NMMA). In a subgroup of 20 patients we also studied the effects of a 3-day treatment regimen. RESULTS Compared to placebo treatment, rosuvastatin decreased LDL-cholesterol levels both after 3 days and 6 weeks of treatment. The decrease in RPF in response to L-NMMA was significantly more pronounced after 6-week therapy with rosuvastatin compared to placebo (-13.7+/-1.0% versus -11.3+/-0.7%; p=0.046), indicating increased basal NOS activity with rosuvastatin treatment. A trend towards improved basal NOS activity was already evident after 3-day treatment. CONCLUSION Treatment with rosuvastatin improved basal NOS activity in the renal circulation of hypercholesterolemic patients, suggestive of a nephroprotective effect. In view of the close relation between altered renal function and cardiovascular events, these nephroprotective effects may contribute to the improved CV prognosis associated with statin treatment.
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Affiliation(s)
- Christian Ott
- Department of Nephrology and Hypertension, University of Erlangen-Nürnberg, Germany
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Basal nitric oxide synthase activity is a major determinant of glomerular haemodynamics in humans. J Hypertens 2008; 26:110-6. [DOI: 10.1097/hjh.0b013e3282f1a93e] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Schlaich MP, Delles C, Schmieder RE. Involvement of endothelial mechanisms in L-arginine-induced alterations of renal haemodynamics in humans. J Hypertens 2007; 25:1515-6; author reply 1516-7. [PMID: 17563580 DOI: 10.1097/hjh.0b013e328182d54d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Martin FL, Supaporn T, Chen HH, Sandberg SM, Matsuda Y, Jougasaki M, Burnett JC. Distinct roles for renal particulate and soluble guanylyl cyclases in preserving renal function in experimental acute heart failure. Am J Physiol Regul Integr Comp Physiol 2007; 293:R1580-5. [PMID: 17670861 DOI: 10.1152/ajpregu.00284.2007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Worsening renal function in the setting of human acute heart failure (AHF) predicts poor outcomes, such as rehospitalization and increased mortality. Understanding potential renoprotective mechanisms is warranted. The guanylate cyclase (GC) enzymes and their second messenger cGMP are the target of two important circulating neurohumoral systems with renoprotective properties. Specifically, natriuretic peptides (NP) released from the heart with AHF target particulate GC in the kidney, while the nitric oxide (NO) system is an activator of renal soluble GC. We hypothesized that both systems are essential to preserve renal excretory and hemodynamic function in AHF but with distinct roles. We investigated these roles in three groups of anesthetized dogs (6 each) with AHF induced by rapid ventricular pacing. After a baseline AHF clearance, each group received intrarenal vehicle (control), N(G)-monomethyl-l-arginine (l-NMMA), a competitive NO inhibitor (50 microg.kg(-1).min(-1)) or a specific NP receptor antagonist, HS-142-1 (0.5 mg/kg). We observed that intrarenal l-NMMA decreased renal blood flow (RBF) without significant decreases in glomerular filtration rate (GFR), urinary sodium excretion (UNaV), or urinary cGMP. In contrast, HS-142-1 resulted in a decrease in UNaV and cGMP excretion together with a reduction in GFR and an increase in distal fractional tubular sodium reabsorption. We conclude that in AHF, the NP system plays a role in maintaining sodium excretion and GFR, while the function of NO is in the maintenance of RBF. These studies have both physiological and therapeutic implications warranting further research into cardiorenal interactions in this syndrome of AHF.
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Affiliation(s)
- Fernando L Martin
- Cardiorenal Research Laboratory, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St. SW, Gugg. 9-01, Rochester, MN 55905, USA.
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Schmieder RE, Delles C, Mimran A, Fauvel JP, Ruilope LM. Impact of telmisartan versus ramipril on renal endothelial function in patients with hypertension and type 2 diabetes. Diabetes Care 2007; 30:1351-6. [PMID: 17337492 DOI: 10.2337/dc06-1551] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE One of the earliest signs of vascular change is endothelial dysfunction, which is also known to provoke albuminuria and to predict cardiovascular prognosis. The aim of this study was to analyze the effects of renin-angiotensin system (RAS) blockade on renal endothelial function. RESEARCH DESIGN AND METHODS In a multicenter, prospective, double-blind, forced-titration, randomized study, 96 patients with type 2 diabetes, hypertension, glomerular filtration rate >80 ml/min, and normo- or microalbuminuria were treated once daily with 40/80 mg telmisartan or 5/10 mg ramipril for 9 weeks. RESULTS The mean +/- SE fall in renal plasma flow (RPF) in response to intravenous N(G)-monomethyl-L-arginine (L-NMMA), reflecting the magnitude of nitric oxide (NO) activity, increased with telmisartan from 71.9 +/- 9.0 ml/min before therapy to 105.2 +/- 9.7 ml/min at the end of treatment (P < 0.001). With ramipril, RPF response to L-NMMA increased from 60.1 +/- 12.2 to 87.8 +/- 9.2 ml/min (P = 0.018). The adjusted difference between treatments was -17.1 +/- 13.7 ml/min (P = 0.214). In accordance, telmisartan increased RPF at rest (i.e., without L-NMMA) from 652.0 +/- 27.0 to 696.1 +/- 31.0 ml/min (P = 0.047), whereas ramipril produced no significant changes in RPF. The more the basal NO activity improved, the greater was the vasodilatory effect on renal vasculature (r = 0.47, P < 0.001). CONCLUSIONS In patients with type 2 diabetes, telmisartan and ramipril both increased NO activity of the renal endothelium significantly, which in turn may support the preservation of cardiovascular and renal function.
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Affiliation(s)
- Roland E Schmieder
- Department of Nephrology and Hypertension, University of Erlangen-Nürnberg, Erlangen, Germany.
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Schlaich MP, Schmieder RE. Contribution of Endothelial Nitric Oxide to Blood Pressure in Humans. Hypertension 2007; 49:e29; author reply e30. [PMID: 17339534 DOI: 10.1161/hypertensionaha.107.087536] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Schäufele TG, Schlaich MP, Delles C, Klingbeil AU, Fleischmann EH, Schmieder RE. Impaired basal NO activity in patients with glomerular disease and the influence of oxidative stress. Kidney Int 2006; 70:1177-81. [PMID: 16883318 DOI: 10.1038/sj.ki.5001745] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Endothelial dysfunction has been found to be linked to and predictive of cardiovascular events. Whether endothelial function of the renal vasculature is impaired in patients with chronic glomerular disease and whether oxidative stress is of importance in this setting has not yet been determined. In this study, endothelial function of the renal vasculature was investigated in 25 patients with chronic glomerular disease and 50 control subjects matched for age and blood pressure. Renal plasma flow (RPF) and glomerular filtration rate were measured by constant infusion input clearance technique at baseline and following infusions of the nitric oxide synthase (NOS) inhibitor N(G)-monomethyl-L-arginine (L-NMMA, 4.25 mg/kg), the substrate of NOS L-arginine (100 mg/kg) and the antioxidant vitamin C (3 g co-infused with L-arginine 100 mg/kg). At baseline, RPF was similar in the two groups. The reduction in RPF in response to L-NMMA was less pronounced in patients with chronic glomerular disease compared to control subjects (-4.6+/-12 vs -9.8+/-9%; P=0.040), indicating reduced basal nitric oxide (NO) activity in chronic glomerular disease. Co-infusion of the antioxidant vitamin C on top of L-arginine induced a more pronounced increase in RPF in patients with chronic glomerular disease than in control subjects (21.7+/-17 vs 10.9+/-22%; P=0.036). Our findings suggest that basal NO activity of the renal vasculature is reduced in patients with chronic glomerular disease compared to age- and blood pressure-matched control subjects. This might be in part related to increased oxidative stress.
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Affiliation(s)
- T G Schäufele
- Department of Medicine 4/Nephrology and Hypertension, University of Erlangen-Nürnberg, Erlangen, Germany
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Michelson G, Wärntges S, Harazny J, Oehmer S, Delles C, Schmieder RE. EFFECT OF NOS INHIBITION ON RETINAL ARTERIAL AND CAPILLARY CIRCULATION IN EARLY ARTERIAL HYPERTENSION. Retina 2006; 26:437-44. [PMID: 16603964 DOI: 10.1097/01.iae.0000238550.74626.e5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
BACKGROUND Arterial hypertension is involved in the pathogenesis of end organ damage by influencing the ability of the vascular endothelium to produce nitric oxide (NO). This study analyzes changes of retinal and systemic NO-dependent circulation parameters by inhibiting nitric oxide synthase (NOS) in both hypertensive and normotensive individuals. METHODS In a double-blind crossover trial, 19 hypertensive patients (H, age 28.2 +/- 0.9 years) and 19 normotensive controls (N, age 26.9 +/- 0.9 years) were randomized treated either with candesartan or placebo. Both retinal capillary flow (RCF) and mean blood flow velocity of the central retinal artery (VCRA) were registered before and after NOS inhibition with N-monomethyl-L-arginine (L-NMMA, 3 mg/kg). In a subpopulation mean arterial pressure (MAP), cardiac output (CO), and the total peripheral resistance (TPR) were determined simultaneously. RESULTS Changes from baseline: In normotensive and hypertensive subjects infusion of L-NMMA led to an increase of MAP (N, +13.3 +/- 1.8%, P < 0.01; H, +14.3 +/- 2.4%, P < 0.01) and TPR (N, +36.9 +/- 3.8%, P < 0.01; H, +45.0 +/- 4.5%, P < 0.01), and to a decrease of CO (N, -21.1 +/- 1.5%, P < 0.01; H, -24.6 +/- 2.3%, P < 0.01). The L-NMMA effect on VCRA and RCF differed between controls and hypertensives. VCRA changed by + 17.3 +/- 6.2% (P < 0.05) and RCF by -7.3 +/- 3.0% (P < 0.05) in controls. In hypertensive subjects corresponding results were + 9.5 +/- 5.2% (P = NS) and + 2.7 +/- 3.8% (P = NS), respectively. The decrease of RCF due to L-NMMA was reduced in hypertension as compared to controls (P < 0.05). The calculated cross-sectional area of CRA was reduced by -58.7% in controls and increased by + 31.1% in hypertensive subjects. There was no significant correlation between the flow in the systemic and retinal circulation. CONCLUSION Only normotensives L-NMMA induces an acceleration of VCRA due to a probable vasoconstriction of the central retinal artery and despite of a reduced RCF. Already in early hypertension the NOS-dependent vascular tone in retinal arteries and capillaries is impaired. The regulation of the retinal capillary flow appeared to be independent from systemic circulation.
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Affiliation(s)
- Georg Michelson
- Augenklinik mit Poliklinik, Universität Erlangen-Nürnberg, Schwabachanlage 6, D-91053 Erlangen, Germany.
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Abstract
PURPOSE OF REVIEW To review the influence of antihypertensive therapy on the contribution of nitric oxide (NO) to renal perfusion in essential hypertension. RECENT FINDINGS The contribution of endothelium-derived NO to renal perfusion can be examined in detail by studying isolated glomerular arterioles and by immunohistochemical techniques. Only few functional studies in human arterial hypertension exist analysing the role of NO for renal perfusion and the change in renal NO bioavailability due to arterial hypertension and its modification by antihypertensive therapy. SUMMARY NO critically contributes to renal perfusion. There is evidence of reduced but also of unchanged NO bioavailability in the renal vasculature of patients with arterial hypertension both from protein expression and functional studies. In particular, drugs interacting with the renin-angiotensin-aldosterone system (angiotensin-converting enzyme inhibitors, angiotensin receptor blockers and aldosterone antagonists) and third-generation beta blockers are promising candidates to improve renal endothelial function. It is not yet clear whether these specific effects translate into prevention of nephrosclerosis.
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Affiliation(s)
- Christian Delles
- Department of Medicine IV, University of Erlangen-Nürnberg, Germany
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Delles C, Michelson G, Harazny J, Oehmer S, Hilgers KF, Schmieder RE. Impaired endothelial function of the retinal vasculature in hypertensive patients. Stroke 2004; 35:1289-93. [PMID: 15073389 DOI: 10.1161/01.str.0000126597.11534.3b] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Arterial hypertension constitutes a central factor in the pathogenesis of stroke. We examined endothelial function of the retinal vasculature as a model of the cerebral circulation. METHODS Thirty-eight young subjects (19 hypertensive and 19 normotensive) were treated with the AT1-receptor blocker candesartan cilexetil and placebo, each over 7 days. Retinal capillary flow and blood flow velocity in the central retinal artery were assessed with scanning laser Doppler flowmetry and pulsed Doppler ultrasound, respectively. N(G)-monomethyl-L-arginine (L-NMMA) was infused to inhibit nitric oxide (NO) synthesis. Diffuse luminance flicker was applied to stimulate NO release. RESULTS In normotensive subjects, L-NMMA decreased retinal capillary flow by 8.2%+/-13% (P<0.05) and flickering light increased mean blood flow velocity in the central retinal artery by 19%+/-29% (P<0.01). In contrast, no significant change to these provocative tests was seen in hypertensive subjects. Treatment with candesartan cilexetil restored a normal pattern of reactivity in retinal capillaries (l-NMMA: decrease in perfusion by 10%+/-17%, P<0.05) and the central retinal artery (flicker: increase in mean blood flow velocity by 42%+/-31%, P<0.001) in hypertensive patients. CONCLUSIONS Endothelial function of the retinal vasculature is impaired in early essential hypertension but can be improved by AT1-receptor blockade.
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Affiliation(s)
- Christian Delles
- Department of Nephrology, University of Erlangen-Nürnberg, Erlangen, Germany
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Delles C, Klingbeil AU, Schneider MP, Handrock R, Schäufele T, Schmieder RE. The role of nitric oxide in the regulation of glomerular haemodynamics in humans. Nephrol Dial Transplant 2004; 19:1392-7. [PMID: 15004251 DOI: 10.1093/ndt/gfh187] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND According to experimental data, the afferent glomerular arteriole is particularly under control of nitric oxide (NO). By use of pharmacological manoeuvres, we examined whether this finding holds true in the human renal circulation in vivo. METHODS Seventy-seven volunteers (aged 50+/-9 years) with mild to moderate essential hypertension (n = 57) or arterial normotension (n = 20) were examined. Basal NO activity in the renal circulation was assessed by the change of renal plasma flow (RPF) through systemic infusion of the NO synthase inhibitor, N(G)-monomethyl-L-arginine (L-NMMA; 4.25 mg/kg). Hypertensive patients were treated over 8 weeks with either the calcium-channel blocker amlodipine or the AT(1)-receptor blocker valsartan, primarily dilating the afferent and efferent arteriole, respectively. Subsequently, renal haemodynamics and NO activity in the renal circulation were determined again. RESULTS L-NMMA reduced RPF in normotensive (by 57+/-70 ml/min/1.73 m(2); P<0.01) and hypertensive subjects (by 46+/-56 ml/min/1.73 m(2); P<0.001) with no significant difference between the two groups. The decrease of RPF through L-NMMA was closely related with the glomerular filtration rate (GFR; r = 0.39, P<0.001). Administration of amlodipine increased GFR by 7.1+/-12.1 ml/min/1.73 m(2); (P<0.01) and in parallel reduced the response of RPF to L-NMMA to 19+/-48 ml/min/1.73 m(2); (P<0.05). In contrast, valsartan maintained GFR and left the response of RPF to L-NMMA unchanged. CONCLUSIONS NO plays an important role in the regulation of human glomerular haemodynamics, probably with a greater contribution to afferent than to efferent arteriolar tone in man.
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Affiliation(s)
- Christian Delles
- Department of Medicine IV/4, University of Erlangen-Nuremburg, Erlangen, Germany
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