[Candesartan cilexetil: pharmacological properties and protective effects against organ damage of a novel nonpeptide angiotensin II-receptor antagonist]

The Effects of Angiotensin II or Angiotensin 1-7 on Rat Pial Microcirculation during Hypoperfusion and Reperfusion Injury: Role of Redox Stress

Renin-angiotensin systems produce angiotensin II (Ang II) and angiotensin 1-7 (Ang 1-7), which are able to induce opposite effects on circulation. This study in vivo assessed the effects induced by Ang II or Ang 1-7 on rat pial microcirculation during hypoperfusion-reperfusion, clarifying the mechanisms causing the imbalance between Ang II and Ang 1-7. The fluorescence microscopy was used to quantify the microvascular parameters. Hypoperfusion and reperfusion caused vasoconstriction, disruption of blood-brain barrier, reduction of capillary perfusion and an increase in reactive oxygen species production. Rats treated with Ang II showed exacerbated microvascular damage with stronger vasoconstriction compared to hypoperfused rats, a further increase in leakage, higher decrease in capillary perfusion and marker oxidative stress. Candesartan cilexetil (specific Ang II type 1 receptor (AT₁R) antagonist) administration prior to Ang II prevented the effects induced by Ang II, blunting the hypoperfusion-reperfusion injury. Ang 1-7 or ACE2 activator administration, preserved the pial microcirculation from hypoperfusion-reperfusion damage. These effects of Ang 1-7 were blunted by a Mas (Mas oncogene-encoded protein) receptor antagonist, while Ang II type 2 receptor antagonists did not affect Ang 1-7-induced changes. In conclusion, Ang II and Ang 1-7 triggered different mechanisms through AT₁R or MAS receptors able to affect cerebral microvascular injury.

Absence of interactive effects of trans-1,2-cyclohexanediol, a major metabolite of the side-chain of candesartan cilexetil, on digoxin-induced arrhythmias in dogs

trans-1,2-Cyclohexanediol, the major metabolite of the cilexetil moiety of candesartan cilexetil (CC), has been reported to have potent pro-arrhythmic effects in dogs with congestive heart failure (CHF), especially when co-administered with digoxin. To verify this and to clarify the clinical relevance and the underlying mechanisms, a series of in vivo and in vitro experiments was conducted. When CC up to 300 mg/kg was administered orally to intact dogs, no changes in the electrocardiograms (ECG) or the required cumulative doses of ouabain to induce ventricular arrhythmias were observed. In dogs with CHF, intravenous bolus administration of trans-1,2-cyclohexanediol at 4 mg/kg followed by continuous infusion at 0.1 mg x kg(-)(1) x min(-)(1) had no effects on the ECG parameters, the type, incidence, and onset time of digoxin-induced arrhythmias or the metabolism of digoxin. In an in vitro experiment using isolated guinea pig papillary muscle, trans-1,2-cyclohexanediol (1 - 100 micromol/L) showed no effects on any parameter of the action potentials. Because no effects were observed in these experiments where the exposure levels of trans-1,2-cyclohexanediol were extremely high compared to those in humans given the maximum therapeutic dose of CC, it is unlikely that CC would induce arrhythmias in clinical use even in patients treated with cardiac glycosides.

Effects of benidipine and candesartan on kidney and vascular function in hypertensive Dahl rats

We examined the effect of the dihydropyridine calcium channel blocker (CCB) benidipine, the angiotensin II type 1 receptor blocker (ARB) candesartan, and the combination of these drugs on blood pressure and kidney and vascular function in rats with salt-induced hypertension. Dahl salt-sensitive (DS) rats were fed with a high-salt (8% NaCl) diet from 7 weeks of age. Benidipine (1, 3 mg/kg), candesartan (1, 3 mg/kg), benidipine (3 mg/kg) combined with candesartan (3 mg/kg), or vehicle was administered orally after the start of the feeding. Relaxant responses to acetylcholine (an endothelium-dependent vasodilator) and sodium nitroprusside (an endothelium-independent vasodilator) were measured to examine the vascular function. DS rats fed the high-salt diet showed an increase in systolic blood pressure (SBP), which was accompanied by glomerular sclerosis and an increase in urinary albumin excretion. Relaxant responses to acetylcholine and sodium nitroprusside were impaired in superior mesenteric arterial rings from the hypertensive DS rats. SBP was significantly lower in all of the drug-treated groups than in the vehicle-treated group. The antihypertensive effect of benidipine at 3 mg/kg was more potent than that of candesartan at 3 mg/kg. The albuminuria was significantly decreased in the benidipine and benidipine plus candesartan groups, but not in the candesartan group. The level of SBP in the benidipine plus candesartan group was lower than that by either drug alone. In addition, benidipine alone and benidipine plus candesartan inhibited the glomerular sclerosis and the impairment of relaxant responses in the arteries. These results demonstrate that benidipine is more effective than candesartan in lowering blood pressure and preventing the impairment of kidney and vascular function in salt-sensitive hypertensive rats. In addition, the results suggest that combination therapy with benidipine and an ARB decreases blood pressure more effectively than either drug alone and may be useful for the treatment of hypertension.

Renoprotective Effects of Benidipine in Combination with Angiotensin II Type 1 Receptor Blocker in Hypertensive Dahl Rats

We examined the effects of the angiotensin II type 1 receptor blocker candesartan, the calcium channel blockers benidipine and amlodipine, hydralazine, and the combination of candesartan and benidipine or amlodipine on blood pressure and renal function in Dahl salt-sensitive (DS) hypertensive rats. Male DS rats (5 weeks of age) were fed a high-salt (8% NaCl) diet, resulting in hypertension accompanied by glomerular sclerosis and an increased urinary albumin excretion. Drugs were orally administered from 2 to 6 weeks after the start of the feeding. Although candesartan (1 or 10 mg/kg) had little effect on the blood pressure, benidipine (4 mg/kg), amlodipine (4 mg/kg) and hydralazine (5 mg/kg) had similar hypotensive effects. Benidipine, but not amlodipine, hydralazine, or candesartan, significantly inhibited the increase in the albuminuria and glomerular sclerosis. The combination of candesartan (1 mg/kg) and benidipine (4 mg/kg) lowered the levels of blood pressure and albuminuria more effectively than the combination of candesartan (1 mg/kg) and amlodipine (4 mg/kg). These results indicate that benidipine is effective in preventing the impairment of renal function in DS hypertensive rats, and suggest that additional benefits can be expected by combination therapy with benidipine and an angiotensin II type 1 receptor blocker.