PubMed Health⌕ Search

Biomedical subjects

Leopoldo Raij

Publications and source records attributed to Leopoldo Raij.

31 records · Page 2Linked to original sources
PubMed2004

Inhibition of oxidative stress and improvement of endothelial function by amlodipine in angiotensin II-infused rats.

BACKGROUND: Calcium channel blockers such as amlodipine are effective antihypertensive agents. In this study we investigated the effects of amlodipine on vascular oxidative stress, expression of the lectin-like oxidized low-density lipoprotein receptor (LOX-1), and endothelial function in angiotensin (Ang) II-infused rats. METHODS: Sprague-Dawley rats were treated with Ang II (0.7 mg/kg/day subcutaneously injected by mini-pump), with or without amlodipine (10 mg/kg/day by gavage), for 5 days and compared with control rats. Levels of aortic ring superoxide (O(2)(-)) and peroxynitrite (ONOO(-)) were determined, and systolic blood pressure (SBP) and endothelium-dependent relaxation were evaluated. RESULTS: Compared with control rats, Ang II-infused rats developed hypertension (175 +/- 3 v 135 +/- 2 mm Hg, P <.05), aortic hypertrophy (16.9 +/- 1.3 v 13.2 +/- 0.3 mg/cm, P <.05), left ventricular hypertrophy (0.236 +/- 0.003 v 0.204 +/- 0.004 g/100 g body weight, P <.05), and impaired endothelium-dependent relaxation (ED(50): 6.6 +/- 0.2 v 8.0 +/- 0.2 -log mol/L acetylcholine concentration, P <.05). Compared with control rats, Ang II-infused rats also had higher aortic levels of LOX-1 mRNA expression, O(2)(-)production (1005 +/- 140 v 608 +/- 159 counts/min/mg, P <.05), ONOO(-) production (1875 +/- 295 v 782 +/- 115 counts/min/mg, P <.05), and plasma free 8-F(2)alpha-isoprostanes (67.4 +/- 19.1 v 27.2 +/- 6.1 pg/mL, P <.05). In Ang II-infused rats SBP, aortic hypertrophy, endothelial dysfunction, LOX-1 expression, aortic O(2)(-) and ONOO(-) production, and plasma free 8-F(2)alpha-isoprostane levels were significantly reduced by amlodipine treatment. CONCLUSIONS: Amlodipine has antihypertensive and antioxidant activity in vivo, which effectively inhibits many of the oxidative stress-dependent mechanisms involved in Ang II-mediated cardiovascular injury.

Amlodipine↗
PubMed2004

Nitric oxide, angiotensin II, and hypertension.

Although initially adaptive, the changes that accompany hypertension, namely, cell growth, endothelial dysfunction, and extracellular matrix deposition, eventually can become maladaptive and lead to end-organ disease such as heart failure, coronary artery disease, and renal failure. A functional imbalance between angiotensin II (Ang II) and nitric oxide (NO) plays an important pathogenetic role in hypertensive end-organ injury. NO, an endogenous vasodilator, inhibitor of vascular smooth muscle and mesangial cell growth, and natriuretic agent, is synthesized in the endothelium by a constitutive NO synthase. NO antagonizes the effects of Ang II on vascular tone, cell growth, and renal sodium excretion, and also down-regulates the synthesis of angiotensin-converting enzyme (ACE) and Ang II type 1 receptors. On the other hand, Ang II decreases NO bioavailability by promoting oxidative stress. A better understanding of the pathophysiologic mechanisms involved in hypertensive end-organ damage may aid in identifying markers of cardiovascular susceptibility to injury and in developing therapeutic interventions. We propose that those antihypertensive agents that lower blood pressure and concomitantly restore the homeostatic balance of vasoactive agents such as Ang II and NO within the vessel wall would be more effective in preventing or arresting end-organ disease.

Angiotensin II↗
PubMed2004

The pharmacokinetics and hemodynamics of sildenafil citrate in male hemodialysis patients.

BACKGROUND: Erectile dysfunction (ED) is highly prevalent in men with renal disease. The clearance of sildenafil citrate, a highly effective oral treatment for ED, is decreased in men with severe renal insufficiency, but the pharmacokinetic and hemodynamic profiles during maintenance hemodialysis in men with end-stage renal disease have not been studied. METHODS: Fifteen men undergoing chronic outpatient maintenance hemodialysis received a single 50-mg oral dose of sildenafil on 2 occasions, once 2 hours before, and once 2 hours after hemodialysis, with randomized assignment to sequence. Blood and dialysate samples were collected, and hemodynamic measurements were made. RESULTS: Hemodialysis did not significantly clear either sildenafil or its primary metabolite, UK-103,320. Administration after hemodialysis was associated with a 17% higher peak plasma concentration and earlier time to peak, which were not clinically meaningful, whereas the overall extent of absorption and the elimination half-life were not affected. The average extent of drug bound to plasma protein was approximately 96% in hemodialysis patients. Intradialytic hypotension was not observed more frequently when sildenafil was administered before hemodialysis. Systolic blood pressure tended to decrease less during hemodialysis when subjects were treated with sildenafil before dialysis. CONCLUSION: The present study demonstrates that sildenafil is not cleared by hemodialysis, and the pharmacokinetic profile resembles more closely that observed in normal volunteers than that observed in patients with severe renal insufficiency. In addition, we found that sildenafil does not promote intradialytic hypotension.

Adult↗
PubMed2003

Postovariectomy hypertension is linked to increased renal AT1 receptor and salt sensitivity.

The functional balance between angiotensin II (Ang II) and nitric oxide (NO) plays a key role in modulating salt sensitivity. Estrogen has been shown to downregulate angiotensin type 1 (AT1) receptor expression and to increase the bioavailability of endothelium-derived NO, which decreases AT1 receptor expression. The present study tests the hypothesis that in the presence of genetic salt sensitivity, deficiency of endogenous estrogens after ovariectomy (OVX) fosters an upregulation of Ang II. Female Dahl salt-resistant (DR), Dahl salt-sensitive (DS), Wistar-Kyoto (WKY), and spontaneously hypertensive (SHR) rats underwent bilateral OVX or sham surgery (SHX) and were fed a normal salt diet (0.5% NaCl) for 14 weeks. Systolic blood pressures were measured every 2 weeks and were not significantly different between OVX and SHX for DR, WKY, and SHR groups. However, at the end of 14 weeks of normal salt diet, hypertension developed in DS OVX but not SHX rats (160+/-3 versus 136+/-3 mm Hg; P<0.05). Hypertension also developed in DS OVX rats pair-fed a normal salt diet (166+/-7 mm Hg). Development of hypertension in DS OVX rats was prevented by estrogen replacement (132+/-3 mm Hg), AT1 receptor blockade (119+/-3 mm Hg), or feeding a very low salt diet (0.1% NaCl; 129+/-4 mm Hg). Renal AT1 receptor protein expression was significantly elevated 2-fold in DS OVX relative to SHX rats and was prevented by estrogen replacement. These data strongly suggest that after OVX in salt-sensitive rats there is a lower threshold for the hypertensinogenic effect of salt that is linked to an activation of Ang II.

Angiotensin II Type 1 Receptor Blockers↗
PubMed2003

In salt-sensitive hypertension, increased superoxide production is linked to functional upregulation of angiotensin II.

The balance between endothelial nitric oxide (NO) and angiotensin II (Ang II) maintains the homeostasis of the cardiovascular and renal systems. We tested the hypothesis that increased oxidant stress linked to a functional imbalance between NO and Ang II might play a central pathogenetic role in salt-sensitive (SS) hypertension. We studied Dahl SS (DS) rats during the prehypertensive (5 days) and hypertensive (12 weeks) phases of a high-salt (4% NaCl) diet. Control rats received a normal-salt (0.5% NaCl, [NS]) diet. Prehypertensive DS rats (systolic blood pressure [SBP] 138+/-2 mm Hg) manifested a 35% increase (P<0.05) in aortic superoxide (O2-) production without evidence of end-organ damage. Hypertensive DS rats (SBP 214+/-11 mm Hg) had impaired endothelium-dependent relaxation (EDR) and increased aortic O2- production (320%), urinary isoprostane excretion (83%), aortic (20%) and left ventricular (LVH, 21%) hypertrophy, and proteinuria (124%). In prehypertensive DS rats, candesartan (10 mg x kg(-1) x d(-1)) an Ang II type 1 receptor blocker (ARB), normalized O2- production. In hypertensive DS rats, the ARB decreased aortic O2- production by 71% and normalized EDR without affecting SBP (212+/-8 mm Hg), aortic hypertrophy, LVH, or proteinuria. Switching hypertensive DS rats to an NS diet did not affect SBP (208+/-8 mm Hg), LVH, aortic hypertrophy, or proteinuria and had minimal effects on O2- and EDR. Concomitant ARB administration plus a switch to an NS diet normalized SBP (138+/-8 mm Hg) as well as end-organ damage. Dahl salt-resistant rats fed an HS diet for 12 weeks did not show hypertension or increased O2- production. Thus, SS hypertension might represent a specific vascular diathesis linked to functional upregulation of Ang II action (increased O2- synthesis) accompanied by insufficient NO bioavailability, which promotes severe endothelial dysfunction.

Angiotensin II↗
PubMed2003

GLUT-1 overexpression: Link between hemodynamic and metabolic factors in glomerular injury?

Mesangial matrix deposition is the hallmark of hypertensive and diabetic glomerulopathy. At similar levels of systemic hypertension, Dahl salt-sensitive but not spontaneously hypertensive rats (SHR) develop glomerular hypertension, which is accompanied by upregulation of transforming growth factor beta1 (TGF-beta1), mesangial matrix expansion, and sclerosis. GLUT-1 is ubiquitously expressed and is the predominant glucose transporter in mesangial cells. In mesangial cells in vitro, GLUT-1 overexpression increases basal glucose transport, resulting in excess fibronectin and collagen production. TGF-beta1 has been shown to upregulate GLUT-1 expression. We demonstrated that in hypertensive Dahl salt-sensitive (S) rats fed 4% NaCl (systolic blood pressure [SBP]: 236+/-9 mm Hg), but not in similarly hypertensive SHR (SBP: 230+/-10 mm Hg) or their normotensive counterparts (Dahl S fed 0.5% NaCl, SBP: 145+/-5 mm Hg; and Wistar-Kyoto, SBP: 137+/-3 mm Hg), there was an 80% upregulation of glomerular GLUT-1 protein expression (P< or =0.03). This was accompanied by a 2.7-fold upregulation of TGF-beta1 protein expression in glomeruli of DSH compared with DSN rats (P=0.02). TGF-beta1 expression was not upregulated and did not differ in the glomeruli of Wistar-Kyoto and SHR rats. As an in vitro surrogate of the in vivo hemodynamic stress imposed by glomerular hypertension, we used mechanical stretching of human and rat mesangial cells. We found that after 33 hours of stretching, mesangial cells overexpressed GLUT-1 (40%) and showed an increase in basal glucose transport of similar magnitude (both P< or =0.01), which could be blocked with an anti TGF-beta1-neutralizing antibody. These studies suggest a novel link between hemodynamic and metabolic factors that may cooperate in inducing progressive glomerular injury in conditions characterized by glomerular hypertension.

Animals↗
PubMed2003

Recommendations for the management of special populations: renal disease in diabetes.

During the past decade, the incidence of end-stage renal disease (ESRD) has risen dramatically, primarily due to an increase in the incidence of diabetes. In patients with diabetes, both hyperglycemia and hypertension are independent risk factors for renal disease. Hypertension is also a risk factor in nondiabetic renal disease and contributes to renal dysfunction by increasing glomerular pressure, glomerular capillary damage, and proteinuria. The resultant nephron damage increases glomerular pressure and damage within remnant functional nephrons, further contributing to deterioration of renal function. In addition to its role in systemic hypertension, angiotensin II has direct effects on the kidney through elevation of glomerular capillary pressure and upregulation of components of the renal injury response. These direct effects of angiotensin II on the kidney support the inclusion of agents that target the renin-angiotensin system (RAS) into treatment regimens for patients at risk for renal disease. Several clinical trials have established the benefits of angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) in patients with diabetes. The ACE inhibitors have been shown to delay renal decline in patients with type 1 diabetes, whereas the renoprotective effect of these agents in patients with type 2 diabetes is less clear. The ARBs have been shown to provide significant benefits in patients with type 2 diabetes, both at early (microalbuminuria) and late (proteinuria) stages of renal decline. In the Irbesartan Diabetic Nephropathy Trial (IDNT) and the Reduction of Endpoints in NIDDM with the Angiotensin II Antagonist Losartan (RENAAL) study, ARB therapy significantly reduced the progression of overt nephropathy (composite of doubling of serum creatinine, ESRD, and death), a benefit that has not been shown for ACE inhibitors. Moreover, in RENAAL, losartan significantly reduced the incidence of the individual end point of ESRD. The benefits of ARB therapy in IDNT and RENAAL were associated with significant reductions in proteinuria and were independent of blood pressure reductions. In RENAAL, proteinuria was a strong predictor of both renal and cardiovascular events. These findings underscore the importance of RAS blockade as a strategy for improving clinical outcomes in patients with renal disease.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2002

Nitric oxide synthase and hypertension.

Nitric oxide, the metabolic product of L-arginine by the enzyme nitric oxide synthase, plays a pivotal role in the regulation of vascular homeostasis. Its complex interaction with the autocrine and paracrine systems, particularly angiotensin II, modulates vasoconstriction and vasodilatation as well as the architectural remodeling of the vascular bed. The major vascular hormones known to be involved are angiotensin II and endothelin-1. Upregulation of endothelin-1, a potent molecule, appears to be a consequence of the nitric oxide-angiotensin II imbalance that contributes to end-organ injury. Increased oxidative stress, common to different diseases including diabetes mellitus and hypertension, is also a determinant player in the interaction between angiotensin II and nitric oxide. The influence of a relative malfunction of the nitric oxide system on the vascular tone and vascular structure, and the effects of hypertension on this system, are discussed.

Animals↗
PubMed2001

Countervailing influence of tumor necrosis factor-alpha and nitric oxide in endotoxemia.

Tumor necrosis factor-alpha (TNF-alpha), a crucial mediator in sepsis, elicits multiple biologic effects, including intravascular thrombosis and circulatory shock. TNF-alpha exerts its biologic effects through two distinct cell surface receptors, TNF-R1 and TNF-R2. The pathophysiologic interaction between TNF-alpha and nitric oxide (NO) in glomerular thrombosis caused by endotoxemia in rats and wild-type mice (C57BL6) as well as in knockout mice that are deficient in TNF-R1 (R1 -/-), TNF-R2 (R2 -/-), or both receptors (R1R2 -/-) was studied. Administration of lipopolysaccharide (LPS; Escherichia coli endotoxin) resulted in increased NO and TNF-alpha production but failed to induce glomerular thrombosis. Concomitant administration of LPS + NG-nitro-L-arginine methyl ester (L-NAME; an NO synthesis inhibitor) resulted in glomerular thrombosis in rats and in wild-type mice. Intraperitoneal administration of pentoxifylline before LPS inhibited TNF-alpha synthesis and prevented glomerular thrombosis in rats given LPS + L-NAME. In contrast to the results observed in rats and wild-type mice, administration of LPS + L-NAME did not result in glomerular thrombosis in knockout mice with either single or double TNF-alpha receptor deletion. Thus, during endotoxemia, (1) TNF-alpha fosters glomerular thrombosis if there is deficiency of NO synthesis and (2) both TNF-alpha receptors are necessary for TNF-alpha's prothrombogenic action. Clinically, these novel studies suggest that in gram-negative endotoxemia, inhibition of NO synthesis and selective blockade of TNF-alpha receptors may provide unique therapeutic approaches for mitigation of glomerular thrombosis and restitution of vascular tone.

Analysis of Variance↗