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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It is well-known that angiotensin converting enzyme (ACE) inhibitor not only decreases blood pressure (BP) but also improves insulin sensitivity. To elucidate the mechanisms of these actions of ACE inhibitor, we evaluated its effect on both BP and insulin sensitivity (M-value) as estimated by the glucose clamp technique in essential hypertensives in comparison with the effect of angiotensin receptor (AT) antagonist. We also evaluated the effect of ACE inhibitor on BP, M-value and muscle fiber composition in fructose-fed rats (FFR) as an insulin-resistant hypertensive model with or without treatment with Hoe 140 (kinin receptor antagonist). In essential hypertensives, both ACE inhibitor and AT antagonist decreased BP and improved insulin sensitivity to the same extent. In FFR, ACE inhibitor also decreased BP and improved insulin sensitivity. Moreover, Hoe 140 showed no effect on these actions of ACE inhibitor. The composite ratio of type I fiber of soleus muscle was decreased significantly in FFR compared to control and ACE inhibitor produced a recovery of the composite ratio of type I fiber to the same as control. These results suggested that muscle fiber composition of skeletal muscle is linked to insulin resistance, and that ACE inhibitor may modulate muscle fiber composition through its vasodilative effect in hypertension. These results also suggest that for vasodilation, it is more important to inhibit angiotensin II than to block degradation of kinins or to improve insulin sensitivity by ACE inhibitor.
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PMID:The mechanisms of insulin sensitivity improving effects of angiotensin converting enzyme inhibitor. 1060 39

One hundred years ago, in 1898, Professor Robert Tigerstedt, Karolinska institutet, Sweden, discovered renin. The subsequent elaboration in 1960 of the renin-angiotensin-aldosterone system signalled the start of modern hypertension research. The kidney takes part in blood pressure regulation in a number of ways. Indications are that increased renovascular resistance due to increased renin-angiotensin activity is of importance for the barostatic function of the kidneys and for the pathogenesis of human hypertension. Several commonly used, efficacious and well tolerated antihypertensive agents act by blocking the renin-angiotensin system, thus normalising kidney function. A number of current large-scale trials--utilising ACE inhibitors and angiotensin receptor antagonists--will, it is hoped, elucidate the proper role of 'anti-renin therapy' in the treatment of hypertension. Thanks to effective modern management of hypertension, renal failure due to hypertensive kidney disease is rare in Sweden today.
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PMID:[A 100-year perspective on renal function and hypertension. Anti-renin therapy has made hypertensive renal failure a rarity]. 1060 12

Left ventricular hypertrophy (LVH), a target-organ response to chronic pressure or volume overload, is associated with its own independent risks of death in patients with hypertension. Numerous studies have shown that LVH increases the risk of coronary heart disease, congestive heart failure, stroke or transient ischemic attack, all-cause deaths, and sudden death. Although the mechanisms by which LVH develops are incompletely understood, the renin-angiotensin system may play an important role. All major classes of antihypertensive agents (calcium channel blockers, diuretics, beta-blockers, angiotensin-converting enzyme inhibitors) can cause LVH regression but not all to the same degree. Angiotensin-converting enzyme inhibitors may provide the most pronounced reduction in left ventricular mass per millimeter of mercury of blood pressure reduction. In addition, animal studies and human trials show promise for the regression of LVH with the use of angiotensin receptor blockers (ARBs). Because ARBs act specifically on the AT(1) receptor, angiotensin II can exert its favorable effects on cell growth inhibition through the AT(2) receptor. One small study that compared the ARB valsartan with atenolol found significant regression of LVH with the ARB by 8 months of treatment.
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PMID:Therapeutic options in minimizing left ventricular hypertrophy. 1061 82

Pharmacologic effects of specific drugs are frequently attributed to their therapeutic class because all agents within a particular class have the same mechanism of action. Because "head-to-head" comparisons in trials are rare, any differentiation between drugs of the same class is usually limited to comparisons of their pharmacokinetic profiles, and it is usually assumed that most of the drugs in a therapeutic class have similar efficacies. Two recent randomized clinical trials demonstrated that the antihypertensive agents irbesartan and losartan, both angiotensin receptor blockers, are not equally effective in reducing blood pressure among patients with hypertension. In both a fixed-dose trial and a titration-protocol trial, patients treated with irbesartan achieved a greater reduction in blood pressure than did those treated with losartan. The response rate was also higher among patients treated with irbesartan. Therefore, irbesartan, used either alone or as a component of response-based combination therapy with a diuretic, is a more potent antihypertensive agent than losartan. These results and the previously published pharmacologic profiles of these drugs demonstrate that angiotensin receptor blockers are, like many other classes of antihypertensive agents, more different than alike.
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PMID:Are there differences among angiotensin receptor blockers? 1061 76

Vasodilator and vasodepressor properties of angiotensins have been reported, and mediation by prostaglandins or nitric oxide has been proposed. Other studies indicate that angiotensin AT(2) receptors might mediate a depressor action, and the present study was designed to delineate and explore this possibility in a conscious rabbit model. Large intravenous boluses of angiotensin III (15 nmol/kg) produced a predictable pressor peak (82+/-4 mm Hg) followed by a depressor phase (20+/-3 mm Hg), whereas equipressor doses of angiotensin II were less effective at producing depressor responses. Angiotensin-(1-7) did not exert a depressor action, and the reduced potency of angiotensin IV (relative to angiotensin III) was similar for both the pressor and depressor phases ( approximately 100-fold). It is clear that specific angiotensin IV or angiotensin-(1-7) receptors do not mediate depressor effects in this model. The AT(1) antagonist losartan (1 mg/kg) blocked both the pressor and depressor components of the angiotensin III response, whereas the AT(2) antagonist PD 123319 (35 mg/kg) had no effect on either element of the response. The data obtained with the angiotensin receptor subtype-selective compounds, losartan and PD 123319, suggest that the depressor action is an AT(1)-mediated effect and give no indication that AT(2) receptors could be involved. Paradoxically, the greater potency of angiotensin III as a vasodepressor belies the conclusion that the response is AT(1)-mediated, because AT(1) receptors have a greater affinity for angiotensin II versus angiotensin III.
Hypertension 2000 Jan
PMID:Angiotensin III depressor action in the conscious rabbit is blocked by losartan but not PD 123319. 1064 87

With the expression cloning of the subunits of the epithelial sodium channel, a new era has evolved in our basic understanding of the low-renin forms of human hypertension. The monogenic hypertensive syndromes manifest dysregulation of the epithelial sodium channel in the cortical collecting tubule. These rare syndromes provide a schema for organizing our thinking about the more common form(s) of low renin hypertension, and raise the possibility that dysregulation of sodium channel activity and consequent salt retention and volume expansion provide a basic pathophysiological mechanism for low-renin hypertension. What are needed are more specific agents to interrupt the mineralocorticoid response pathways, and clinically relevant approaches to measuring sodium channel activity at the level of the collecting tubule in the individual patient. The combined use of aldosterone antagonists and angiotensin-converting enzyme inhibitors or angiotensin receptor antagonists could have a beneficial effect on "progression" of renal disease associated with glomerular and interstitial fibrosis, especially if the effects of hyperkalemia on the heart and aldosterone secretion can be minimized.
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PMID:Low renin hypertension in the next millennium. 1065 Dec 17

This 8-week, open-label study compared the efficacy and safety of once-daily telmisartan, either alone or in combination with hydrochlorothiazide (HCTZ) and amlodipine, with a similar enalapril regimen in patients with severe hypertension. Clinically relevant reductions in supine systolic blood pressure/DBP were observed with telmisartan (14.6/13.2 mmHg) and enalapril (13.0/12.9 mmHg) monotherapy. Incremental reductions were seen with up-titration of monotherapy (telmisartan 8.1/7.4 and enalapril 9.2/7.7 mmHg), and the addition of HCTZ (telmisartan 14.9/8.7 and enalapril 8.0/6.7 mmHg), and amlodipine (telmisartan 8.0/6.5 and enalapril 10.5/6.4). After 8 weeks of treatment, supine DBP control was achieved in 55% and 35% of the patients on the telmisartan and enalapril regimens, respectively. Both treatment regimens were well tolerated. Telmisartan, a new angiotensin receptor blocker, is a safe and effective drug to use in combination for the treatment of patients with severe hypertension and proved at least as effective as the enalapril combination.
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PMID:The efficacy and safety of telmisartan compared to enalapril in patients with severe hypertension. 1066 27

The renin-angiotensin system plays a central role in the regulation of blood pressure through its primary effector hormone angiotensin II. Studies conducted nearly 30 years ago with peptidic angiotensin II receptor blockers (ARB) suggested that disruption of the renin-angiotensin system offered considerable promise for the treatment of hypertension as well as heart failure. This promise was initially realized with the advent of angiotensin converting enzyme inhibitors, and more recently with nonpeptidic ARB that selectively antagonize the AT1-angiotensin receptor subtype. The potent and long-acting agent candesartan cilexetil illustrates how these new ARB fulfill the promises suggested by the early studies. Candesartan cilexetil provides a clinically relevant, dose-dependent reduction in diastolic and systolic blood pressure at doses of 4 to 16 mg once daily in patients with mild to moderate hypertension. Recent studies suggest that further blood pressure lowering is obtained with a 32-mg once daily dose. In comparative clinical trials, 8 mg of candesartan cilexetil and 10 to 20 mg of enalapril provided comparable antihypertensive effects. The safety and tolerability profile of candesartan cilexetil is comparable to placebo. Notably, this agent does not produce the dry, nonproductive cough that often limits use of angiotensin converting enzyme inhibitors, nor does it cause side effects that limit other antihypertensive drug classes. On the basis of the results of initial clinical studies, ARB also possess cardioprotective and renoprotective properties that promise to expand the role that these new agents will play in treating cardiovascular disorders.
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PMID:Update on the clinical pharmacology of candesartan cilexetil. 1067 85

Virtually all of the biological actions of angiotensin II (ANG II) have been thought to be mediated by the type 1 (AT1) angiotensin receptor and the function of the type 2 (AT2) receptor is unknown. We now describe a novel physiological action of ANG II to release nitric oxide (NO) mediated by the AT2 receptor in both the kidney and gastrointestinal tract. We present an integrated model for a counter-regulatory protective action of the AT2 receptor mediated by nitric oxide. In the kidney, ANG II at the AT2 receptor stimulates a vasodilator cascade of bradykinin (BK), NO and cyclic GMP which is tonically activated only during conditions of increased ANG II, such as sodium depletion. In the absence of the AT2 receptor, pressor and antinatriuretic hypersensitivity to ANG II is associated with BK and NO deficiency. In angiotensin-dependent hypertension, the hypotensive effect at AT1 receptor blockade is due at least in part to AT2 receptor stimulation and consequent increased activity of the vasodilator cascade. In the gastrointestinal tract, physiological quantities of ANG II stimulate the AT2 receptor releasing NO and cGMP leading to increased sodium and water absorption. In conclusion, NO is an important physiological mediator of ANG II at the AT2 receptor.
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PMID:Nitric oxide: a physiological mediator of the type 2 (AT2) angiotensin receptor. 1069 81

A growing body of evidence supports the notion that angiotensin II (Ang II), the central product of the renin-angiotensin system, may play a central role not only in the etiology of hypertension but also in the pathophysiology of cardiovascular and renal diseases in humans. In this review, we focus on the role of Ang II in cardiovascular and renal diseases at the molecular and cellular levels and discuss up-to-date evidence concerning the in vitro and in vivo actions of Ang II and the pharmacological effects of angiotensin receptor antagonists in comparison with angiotensin-converting enzyme inhibitors. Ang II, via AT(1) receptor, directly causes cellular phenotypic changes and cell growth, regulates the gene expression of various bioactive substances (vasoactive hormones, growth factors, extracellular matrix components, cytokines, etc.), and activates multiple intracellular signaling cascades (mitogen-activated protein kinase cascades, tyrosine kinases, various transcription factors, etc.) in cardiac myocytes and fibroblasts, vascular endothelial and smooth muscle cells, and renal mesangial cells. These actions are supposed to participate in the pathophysiology of cardiac hypertrophy and remodeling, heart failure, vascular thickening, atherosclerosis, and glomerulosclerosis. Furthermore, in vivo recent evidence suggest that the activation of mitogen-activated protein kinases and activator protein-1 by Ang II may play the key role in cardiovascular and renal diseases. However, there are still unresolved questions and controversies on the mechanism of Ang II-mediated cardiovascular and renal diseases.
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PMID:Molecular and cellular mechanisms of angiotensin II-mediated cardiovascular and renal diseases. 1069 53


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