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

A lot of evidence points to the important role of the renin-angiotensin system in the physiopathology of hypertension and the progression of chronic renal failure. In this review, the authors report the data concerning the protective effects of antagonists of angiotensin II AT1 receptors (AT1ra). The AT1 ra have been shown to have beneficial effects in most experimental models of nephropathy in which they have been tested (renal ischaemia, essential or induced hypertension, glomerulonephritis, 5/6 nephrectomy, renal transplantation, induced diabetes, toxic and radiotherapy-induced nephropathy). Clinical trials confirm these beneficial effects. In healthy subjects and hypertensive patients, the AT1 ra have identical effects to those of angiotensin converting enzyme (ACE) inhibitors on renal haemodynamics. In hypertensives, Candesartan and Irbesartan increase renal blood flow and the glomerular filtration rate and decrease the filtration fraction. Two studies have also shown that Candesartan and Irbesartan reduce proteinuria in diabetic patients. Similar results have been reported in essential hypertension with renal failure. These data suggest that AT1 ra have beneficial effects on the progression of experimental kidney disease and on proteinuria in the clinical setting. Of the pharmacological agents available for use in this class, it is essential to propose molecules whose efficacy in antagonising the effects of angiotensin II lasts throughout the 24 hour period. Clinical trials are under way to evaluate the effects of AT1 ra on renal function in man over a long period.
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PMID:[Are the antagonists of angiotensin II AT1 receptors protectors of the kidney?]. 1044 11

Candesartan (Atacand) is a novel antagonist of angiotensin II AT1 receptors. It is a specific "insurmountable" antagonist which is characterized by its extremely high specificity and its very slow dissociation from the receptor. In the treatment of essential arterial hypertension it appears very efficacious and shows a dose dependent activity within the dose-range of 4 mg to 32 mg/day. The efficacy is maintained up to 36 hours after drug intake. Candesartan is excreted, unchanged, both in the feces (2/3) and urine (1/3). Side-effects are comparable to placebo.
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PMID:[Pharma-clinics. The drug of the month. Candesartan (Atacand)]. 1044 28

Acceptance of the notion that physiologically specific interruption of the renin-angiotensin-aldosterone system (RAAS) is of considerable therapeutic benefit in the treatment of hypertension and congestive heart failure has generated great interest in the search for novel pharmacological inhibitors. The RAAS is expressed at the whole body, organ/tissue and cellular level through the action of the octapeptide angiotensin II (Ang II), the primary effector molecule of the RAAS. The availability of selective, potent, orally active and long-acting nonpeptide Ang II type 1 (AT1) receptor antagonists provided the opportunity to obtain the benefits of selectively blocking the RAAS at the level of the AT1 receptor that mediates most, if not all, of the important actions of Ang II, and avoid the nonspecificity of the Ang I converting enzyme (ACE) inhibitors. Losartan was the first, but by no means remained the only nonpeptide AT1 receptor antagonist. Numerous other "sartans" have emerged in the past several years and successfully completed clinical development. With the exception of Eprosartan, all others, i.e. Candesartan, Irbesartan, Saprisartan, Tasosartan, Telmisartan, Valsartan and Zolasartan, are based on modifications of Losartan's prototypic chemical structure. AT1 receptor antagonists represent the newest addition to the arsenal of cardiovascular therapeutics. The predominant role of the AT1 receptor in mediating the pathophysiological role of Ang II underlies the effectiveness of this novel class of agents to lower arterial blood pressure, reduce pre- and afterload, inhibit sympathetic nervous system activity and prevent cardiovascular hypertrophy and cardiac failure induced by inappropriate control of the RAAS.
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PMID:Angiotensin II receptor antagonists: an emerging new class of cardiovascular therapeutics. 1048 32

Although angiotensin AT1 receptor antagonist(AT1 A) improves insulin sensitivity in insulin resistant models, its effect on spontaneously hypertensive rats(SHR) has not been elucidated. We investigated the effects of AT1 A, candesartan on insulin sensitivity in SHR/Izm and the role of sympathetic activity in its mechanism. In 9-week-old SHR/Izm, candesartan(10 mg/kg/day) was given orally for 5 days. A control group received vehicle. On the 6th day, mean arterial pressure (MAP), heart rate(HR), plasma norepinephrine (PNE), plasma epinephrine(PE) and plasma dopaminc(PDA) were measured in both groups (n = 11 in each group). In the separate groups of rats, fasting blood glucose (FBG), serum sodium, serum potassium and insulin sensitivity by steady state blood glucose (SSBG) were assessed (n = 16 in the Candesartan group and n = 8 in the Control group). MAP and SSBG were significantly lower in the Candesartan group (117 +/- 2 mmHg and 138 +/- 5 mg/dl) than those in the Control group(155 +/- 6 mmHg and 164 +/- 10 mg/dl). Body weight, HR, FBG, PNE, PE, PDA, sodium and potassium were the same between the groups. In conclusion, since AT1 A, candesartal lowers blood pressure and improves insulin sensitivity irrespective of sympathetic activity in SHR/Izm, it is useful in treating hypertension associated with insulin resistance.
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PMID:[Effects of angiotensin II receptor antagonist on insulin sensitivity and sympathetic activity in spontaneously hypertensive rats]. 1057 94

Several angiotensin II receptor blockers (ARB) are currently available for the treatment of hypertension. These drugs share a common mechanism of action-antagonism of angiotensin II AT1 receptors; however, their receptor binding kinetics differ. Candesartan has a higher affinity for the AT1 receptor than all the other ARB. In addition, candesartan and irbesartan block the AT1 receptor with insurmountable antagonism, whereas losartan, valsartan, and eprosartan are competitive antagonists. The pharmacokinetics of these ARB also differ in terms of oral bioavailability, rate of absorption, metabolism, and route and rate of elimination. Both losartan potassium and candesartan cilexetil are prodrugs; however, losartan is partially converted into EXP3174 in the liver, whereas candesartan cilexetil is converted completely into candesartan during gastrointestinal absorption. On the basis of elimination half-lives, losartan, valsartan, and eprosartan may be classified as shorter acting and candesartan cilexetil and irbesartan as longer acting. Each drug effectively lowers blood pressure during once daily administration to patients with mild to moderate hypertension, with candesartan cilexetil requiring the lowest dosage and providing dose-dependent efficacy. Initial comparative clinical trials suggest that both candesartan cilexetil and irbesartan in the doses used are significantly more effective than losartan in lowering trough sitting diastolic blood pressure. It remains to be determined, however, whether the observed pharmacologic and pharmacokinetic differences among the members of the ARB class will have a clinically significant impact on long-term cardiovascular outcomes and reductions of cardiovascular mortality.
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PMID:Newly emerging pharmacologic differences in angiotensin II receptor blockers. 1067 84

Angiotensin II type 1 (AT1) receptor blockers, such as candesartan, are attractive alternatives to ACE inhibitors in the treatment of hypertension and cardiovascular disease. Although angiotensin-converting enzyme (ACE) inhibitors are able to suppress the renin-angiotensin system (RAS), their mechanism of action may limit their clinical utility in the treatment of hypertension. For example, they act as competitive inhibitors of ACE. This means that their effects can be overcome by high levels of angiotensin I, which occur after ACE inhibition due to removal of the negative feedback effect of angiotensin II on renal renin release. ACE inhibitors are also unable to block the production of angiotensin II by non-ACE-mediated pathways. Furthermore, ACE is not a specific enzyme. Its inhibition therefore has effects on other substances, such as bradykinin, leading to the class-specific side effects associated with ACE inhibitors. Candesartan, on the other hand, binds insurmountably to the AT1-receptor, thereby providing more complete blockade of the negative cardiovascular effects of angiotensin II than is possible with ACE inhibitors. The specificity of AT1-receptor blockade also ensures that efficacy is achieved without inducing the side effect of cough that results from the non-specific consequences of ACE inhibition. Preclinical and early clinical studies demonstrate that AT1-receptor blockers produce at least the same degree of target-organ protection as has been demonstrated for ACE inhibitors. Additional benefits of AT1-receptor blockers may arise from the fact that, unlike ACE inhibitors, they do not prevent the activity of angiotensin II on AT2-receptors in the heart, which is thought to reduce cardiac remodelling. From a mechanistic perspective, therefore, AT1-receptor blockers appear to have advantages over ACE inhibitors, in terms of a more complete blockade of angiotensin II effects, while also avoiding the specific side effects associated with ACE inhibition.
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PMID:Angiotensin II type 1 receptor blockade: a novel therapeutic concept. 1105 29

The development of very specific blockers for the angiotensin II type 1 (AT(1)) receptor made it possible to examine the contribution of angiotensin II to normal control mechanisms and disease with a specificity beyond what ACE inhibitors could provide. In the present study, we explored the contribution of angiotensin II to 2 renal mechanisms: renal hemodynamics and the short feedback loop, in which angiotensin II acts as a determinant of renin release. To make that comparison, we studied healthy volunteers in balance on a 10-mmol sodium intake to activate the renin system. Our goal was to compare the relation between the dose of candesartan, an AT(1) receptor blocker, and the renal hemodynamic and hormonal responses. A second goal was to ascertain the relation between time after candesartan administration and the peak response. Twelve healthy subjects (mean age 33+/-2.3 years) in low-sodium balance were administered candesartan in 4-, 8-, 16-, and 32-mg doses. Candesartan produced a dose-related increase in renal plasma flow, with the maximum vasodilator response at 16 mg (142+/-13 mL. min(-1). 1.73 m(-2)) occurring during the first 4 hours after the dose. Likewise, candesartan caused a dose-related rise in plasma renin activity, with 32 mg as the dose producing the greatest response at 4 and 24 hours after administration. The peak plasma renin activity achieved in this study (15.3+/-1.6 ng. L(-1). s(-1); 55.0+/-5.6 ng angiotensin I. mL(-1). h(-1)) was found at the 4- to 8-hour interval after dosing in a subset of subjects (n=5) who received the 16-mg dose 4 hours earlier than the other subjects. On the basis of the difference in the relation between dose and response and the relationship between time after drug administration and response, the determinants of the renal hemodynamic and hormonal response can be said to differ. The remarkable rise in plasma renin activity after candesartan is substantially larger than that in earlier studies with ACE inhibition, providing additional evidence for non-ACE-dependent angiotensin II generation in the kidney.
Hypertension 2000 Nov
PMID:Renal hemodynamic and hormonal responses to the angiotensin II antagonist candesartan. 1108 52

We examined whether nitro-L-arginine-methyl ester (L-NAME) causes a sustained elevation in plasma fibrinogen concentration in rats. Oral dosing of L-NAME (100 mg/kg per day) for 7 days significantly raised plasma fibrinogen concentration in rats. The increase in plasma fibrinogen, however, returned to control levels by the treatment for more than 7 days, in spite of progressive hypertension. Candesartan failed to reverse the transient hyperfibrinogenemia, indicating that the rise in plasma fibrinogen may occur through the mechanisms other than angiotensin II receptor activation. These data suggest that a prolonged L-NAME treatment does not cause chronic hyperfibrinogenemia in rats.
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PMID:Effect of prolonged nitric oxide synthesis inhibition on plasma fibrinogen concentration in rats. 1124 66

The main objective of the CALM (Candesartan And Lisinopril Microalbuminuria) study is to assess the effect of a dual blockade of the renin-angiotensin system--using both an angiotensin converting enzyme inhibitor (ACE-I) and an angiotensin II type 1 receptor blocker--in patients with type 2 diabetes, high blood pressure and microalbuminuria. The study included 200 patients randomized to receive candesartan 16 mg or lisinopril 20 mg for 12 weeks, followed by 12 weeks of the same monotherapy or a combination treatment. Main outcomes are the reduction of microalbuminuria and blood pressure. All three of the treatments are effective, but the dual blockade is respectively 18%, 8 mmHg and 5 mmHg more effective in reducing microalbuminuria, systolic and diastolic blood pressure. No comparison is made between this "new" association and the more frequently used biotherapy (i.e. ACE-I plus thiazidic diuretic) and therefore its usefulness in regular practice is still to be determined.
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PMID:[Clinical study of the month. The CALM study assessing the combination of an angiotensin-converting enzyme inhibitor and an angiotensin II receptor antagonist in the treatment of diabetic nephropathy]. 1129 48

To determine the effects of physiological alterations in endogenous angiotensin II activity on basal renal sympathetic nerve activity (RSNA) and its arterial baroreflex regulation, angiotensin II type 1 receptor antagonists were microinjected into the rostral ventrolateral medulla of anesthetized rats consuming a low, normal, or high sodium diet that were instrumented for simultaneous measurement of arterial pressure and RSNA. Plasma renin activity was increased in rats fed a low sodium diet and decreased in those fed a high sodium diet. Losartan (50, 100, and 200 pmol) decreased heart rate and RSNA (but not mean arterial pressure) dose-dependently; the responses were significantly greater in rats fed a low sodium diet than in those fed a high sodium diet. Candesartan (1, 2, and 10 pmol) decreased mean arterial pressure, heart rate, and RSNA dose-dependently; the responses were significantly greater in rats fed a low sodium diet than in those fed a normal or high sodium diet. [D-Ala(7)]Angiotensin-(1-7) (100, 200, and 1000 pmol) did not affect mean arterial pressure, heart rate, or RSNA in rats fed either a low or a high sodium diet. In rats fed a low sodium diet, candesartan reset the arterial baroreflex control of RSNA to a lower level of arterial pressure, and in rats with congestive heart failure, candesartan increased the arterial baroreflex gain of RSNA. Physiological alterations in the endogenous activity of the renin-angiotensin system influence the bradycardic, vasodepressor, and renal sympathoinhibitory responses to rostral ventrolateral medulla injection of antagonists to angiotensin II type 1 receptors but not to angiotensin-(1-7) receptors.
Hypertension 2001 Apr
PMID:Sodium intake influences hemodynamic and neural responses to angiotensin receptor blockade in rostral ventrolateral medulla. 1130 12


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