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

The phosphodiesterase 5 inhibitor tadalafil has renoprotective effects in a rat model of chronic kidney disease

Phosphodiesterase 5 inhibitors are widely used to treat erectile dysfunction and lower urinary tract symptoms with benign prostatic hyperplasia. Recent studies have indicated the renoprotective effects of this class of compounds. Whether renoprotection depends on blood pressure reduction remains controversial. In this study, we investigated the renoprotective effects of the phosphodiesterase 5 inhibitor, tadalafil, in a rat model of high-salt induced kidney injury with hypertension. Dahl salt-sensitive rats were fed a normal diet, high-salt (8% sodium chloride) diet, or high-salt diet with oral administration of either low- or high-dose tadalafil (1 and 10 mg kg-1  day-1 , respectively). Serum creatinine, urinary protein, and blood pressure were measured at baseline and after 8 weeks, at which point the rats were examined for glomerular injury and fibrosis. PAI1 mRNA levels were also evaluated. After 8 weeks, blood pressure, serum creatinine, and urinary protein levels were significantly higher in the high-salt group than those in the normal-salt group. Serum creatinine and urinary protein were significantly lower in both tadalafil groups than those in the high-salt group, while only high-dose tadalafil affected blood pressure. In addition, glomerulosclerosis and α-smooth muscle actin expression significantly decreased in both tadalafil treatment groups. PAI1 mRNA increased significantly in the high-salt group but decreased in both tadalafil-treated groups. Our results indicated that both low- and high-dose tadalafil prevented fibrosis and glomerular injury in a chronic kidney disease rat model. Mechanistically, these effects may be associated with PAI1 expression and glomerular structure protection.

Benidipine reduces ischemia reperfusion-induced systemic oxidative stress through suppression of aldosterone production in mice

Aldosterone is implicated in the pathogenesis of several cardiovascular diseases, including ischemia reperfusion (I/R) and myocardial infarction, and also causes oxidative stress and inflammation in cardiovascular systems. Benidipine, a long-acting T- and L-type calcium channel blocker, reduces infarct size following myocardial I/R in rabbits. Benidipine also inhibits the production of aldosterone in vitro. However, the precise mechanism of this phenomenon in vivo remains unknown. We therefore evaluated whether benedipine has a beneficial role through the regulation of oxidative stress in myocardial I/R. C57BL/6J mice were subjected to 30 min of left ascending coronary I/R. Benidipine was administered orally at 3 mg kg(-1) daily for 3 weeks without any changes in hemodynamic variables. Benidipine significantly reduced infarction size (13.4±2.5%) compared with controls (25.5±3.6%). Urinary 8-hydroxy-2' deoxyguanosine (8-OHdG), a marker of oxidative DNA damage, increased significantly after I/R. I/R induced increases in 8-OHdG were significantly lower with benidipine. Local myocardial 8-OHdG was also elevated in I/R, but this augmentation was significantly suppressed with benidipine. The plasma aldosterone concentration (PAC) significantly increased 2 days after I/R and remained elevated at least 7 days after I/R. Treatment with benidipine significantly decreased I/R-induced elevation of the PAC. I/R-induced markers of fibrosis in hearts also reduced in benidipine. These results suggest that the administration of benidipine reduces myocardial infarct size as well as systemic oxidative stress after I/R. These phenomena are partially linked to reduced plasma aldosterone levels.

Combination therapy with olmesartan and azelnidipine improves EDHF-mediated responses in diabetic apolipoprotein E-deficient mice

BACKGROUND

The endothelium modulates vascular tone by synthesizing and releasing several vasodilating factors, including vasodilator prostaglandins, nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF). In the present study, we examined whether an angiotensin-receptor blocker, a calcium-channel blocker or their combination improved EDHF-mediated responses in diabetic apolipoprotein E-deficient (ApoE(-/-)) mice.

METHODS AND RESULTS

We used male C57BL/6N (control) and streptozocin-induced diabetic ApoE(-/-) mice. The diabetic ApoE(-/-) mice were administered oral vehicle (untreated), olmesartan (OLM, 30 mgxkg(-1)xday(-1)), azelnidipine (AZL, 10 mgxkg(-1)xday(-1)), their combination (OLM + AZL), or hydralazine (HYD 5 mgxkg(-1)xday(-1)) for 5 weeks. In the untreated group, systolic blood pressure was significantly higher and both EDHF-mediated relaxation and endothelium-dependent hyperpolarization were markedly reduced as compared with the control group. Although EDHF-mediated relaxation was not significantly improved in the HYD, OLM and AZL groups, it was significantly improved in the OLM + AZL group, as was also the case with phosphorylation of Akt and endothelial NO synthase (eNOS). In contrast, the endothelium-independent relaxation response to sodium nitroprusside or NS-1619 (a direct opener of K(Ca) channels) was unaltered in any group.

CONCLUSIONS

OLM + AZL may improve the severely impaired EDHF-mediated responses in diabetic ApoE(-/-) mice, in which activation of the endothelial Akt - eNOS pathway may be involved.

Blockade of T-type voltage-dependent Ca2+ channels by benidipine, a dihydropyridine calcium channel blocker, inhibits aldosterone production in human adrenocortical cell line NCI-H295R

Benidipine, a long-lasting dihydropyridine calcium channel blocker, is used for treatment of hypertension and angina. Benidipine exerts pleiotropic pharmacological features, such as renoprotective and cardioprotective effects. In pathophysiological conditions, the antidiuretic hormone aldosterone causes development of renal and cardiovascular diseases. In adrenal glomerulosa cells, aldosterone is produced in response to extracellular potassium, which is mainly mediated by T-type voltage-dependent Ca2+ channels. More recently, it has been demonstrated that benidipine inhibits T-type Ca2+ channels in addition to L-type Ca2+ channels. Therefore, effect of calcium channel blockers, including benidipine, on aldosterone production and T-type Ca2+ channels using human adrenocortical cell line NCI-H295R was investigated. Benidipine efficiently inhibited KCl-induced aldosterone production at low concentration (3 and 10 nM), with inhibitory activity more potent than other calcium channel blockers. Patch clamp analysis indicated that benidipine concentration-dependently inhibited T-type Ca2+ currents at 10, 100 and 1000 nM. As for examined calcium channel blockers, inhibitory activity for T-type Ca2+ currents was well correlated with aldosterone production. L-type specific calcium channel blockers calciseptine and nifedipine showed no effect in both assays. These results indicate that inhibition of T-type Ca2+ channels is responsible for inhibition of aldosterone production in NCI-H295R cells. Benidipine efficiently inhibited KCl-induced upregulation of 11-beta-hydroxylase mRNA and aldosterone synthase mRNA as well as KCl-induced Ca2+ influx, indicating it as the most likely inhibition mechanism. Benidipine partially inhibited angiotensin II-induced aldosterone production, plus showed additive effects when used in combination with the angiotensin II type I receptor blocker valsartan. Benidipine also partially inhibited angiotensin II-induced upregulation of the above mRNAs and Ca2+ influx inhibitory activities of benidipine for aldosterone production. T-type Ca2+ channels may contribute to additional benefits of this drug for treating renal and cardiovascular diseases, beyond its primary anti-hypertensive effects from blocking L-type Ca2+ channels.

Beneficial Effects of the Combination of Nifedipine and Losartan in Hypertensive Dahl Salt-Sensitive Rats

BACKGROUND

The antihypertensive and organ-protective effects of the combination of the angiotensin II type 1 receptor blocker losartan and the calcium channel blocker nifedipine were examined in Dahl salt-sensitive rats.

METHODS

The rats fed with a high-salt diet developed hypertension accompanied by aorta and heart hypertrophy, and impaired renal function. The animals were treated with losartan (30 mg/kg/day), nifedipine (7.8 mg/kg/day) or with a combination of both drugs for 8 weeks. At the end of the study systolic blood pressure, kidney function, organ weight, and mRNA expression were investigated.

RESULTS

Losartan reduced significantly the systolic blood pressure as well as the aorta and left ventricular hypertrophy. Nifedipine and its combination with losartan had similar effects on the systolic blood pressure, aorta and left ventricular hypertrophy but only the combination treatment reduced the expression of transforming growth factor-beta1 in aorta and brain natriuretic peptide in left ventricle significantly. Nifedipine and the combination therapy reduced proteinuria and improved urine creatinine excretion. The expression of collagen III and IV in the kidney was significantly reduced by the combination therapy.

CONCLUSION

These results indicate that although losartan and nifedipine were effective in lowering blood pressure and showed moderate organ protection, additional benefits can be expected by combination therapy with both compounds.

Benidipine, a dihydropyridine-Ca2+ channel blocker, increases the endothelial differentiation of endothelial progenitor cells in vitro

Benidipine is a dihydropyridine-Ca2+ channel blocker used in the treatment of hypertension and angina pectoris. In the present study, we examined the effects of benidipine on the endothelial differentiation of circulating endothelial progenitor cells (EPCs) using an in vitro culture method. Peripheral blood derived mononuclear cells (PBMCs) containing EPCs were isolated from C57BL/6 mice, and then the cells were cultured on vitronectin/gelatin-coated slide glasses. After 7 days of culture, endothelial cells differentiated from EPCs were identified as adherent cells with 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine-labeled acetylated low density lipoprotein (Dil-Ac-LDL) uptake and lectin binding under a fluorescent microscope. Incubation of PBMCs for 7 days with benidipine (0.01-1 micromol/l) significantly increased the number of Dil-Ac-LDL+/fluorescein isothiocyanate-lectin (FITC-Lectin)+ cells. Wortmannin, a phosphoinositide-3 kinase (PI3K) inhibitor, selectively attenuated the effect of benidipine on the endothelial differentiation. In addition, benidipine treatment augmented the phosphorylation of Akt, indicating that the PI3K/Akt pathway contributed, at least in part, to the endothelial differentiation induced by benidipine. These results suggest that the treatment with benidipine may increase the endothelial differentiation of circulating EPCs and contribute to endothelial protection, prevention of cardiovascular disease, and/or an improvement of the prognosis after ischemic damage.

Comparison of the antiatherosclerotic effects of dihydropyridine calcium channel blocker and HMG-CoA reductase inhibitor on hypercholesterolemic rabbits

The antiatherosclerotic effects of the dihydropyridine-type calcium channel blocker, benidipine hydrochloride (benidipine), and 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, pravastatin sodium (pravastatin), were compared in hypercholesterolemic rabbits. Male, New Zealand white rabbits were fed a 0.5% cholesterol diet. Pravastatin (10 mg/kg) or benidipine (10 mg/kg) was orally administered once daily after start of feeding. After 8 weeks of cholesterol feeding, serum cholesterol was increased and endothelial function of thoracic aorta was impaired. Pravastatin prevented elevation of serum cholesterol and aortic tunica intima hyperplasia. Although benidipine had little effect on serum cholesterol, it significantly inhibited aortic tunica intima hyperplasia and impairment of endothelial function. Expression levels of the vascular cell adhesion molecule-1 (VCAM-1) and lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) mRNA in aorta of hypercholesterolemic rabbit were higher than those of normal rabbit. Benidipine significantly prevented upregulation of VCAM-1 mRNA expression and showed a tendency to inhibit elevation of LOX-1 mRNA expression. Pravastatin significantly prevented upregulation of both VCAM-1 and LOX-1 mRNA expression. The results demonstrate that pravastatin inhibits increase of serum cholesterol and vascular dysfunction in hypercholesterolemic rabbit. Benidipine is effective in preventing vascular hyperplasia without altering serum cholesterol levels and this may be due to inhibition of expression of VCAM-1.

Renoprotective Effect and Cost-Effectiveness of Using Benidipine, a Calcium Channel Blocker, to Lower the Dose of Angiotensin Receptor Blocker in Hypertensive Patients with Albumiuria

In hypertensive patients with chronic renal disease, angiotensin receptor blockers (ARBs) are among the first-line drugs, and calcium channel blockers (CCBs) are recommended as a second line. We examined the effects of two therapeutic strategies using ARBs and benidipine, a CCB, on blood pressure (BP), urinary albumin excretion (UAE), and cost-effectiveness in hypertensive patients with albuminuria. Patients whose BP was 140/90 mmHg or higher despite treatment with low- or medium-dose ARBs were assigned randomly to two groups. In Group A (n=14), the ARB dose was maximized and then benidipine was added until BP targets were reached (<130/85 mmHg). In Group B (n=18), benidipine was administered first and then the ARB dose was increased until BP targets were reached. The BP targets were achieved by ARB alone in 36% of Group A patients and by the addition of benidipine in 83% of Group B patients. Finally, BP decreased in each group, reaching the targets in 93% of Group A patients and 94% of Group B patients after a 4-month therapeutic period. UAE was decreased in both groups after a 4-month therapeutic period compared to the allocation period (-33+/-6% in Group A, -31+/-6% in Group B; p<0.001, respectively). The monthly drug cost was higher (11,426+/-880 vs. 8,955+/-410 yen, p=0.012) and the cost-effectiveness of antihypertensive treatment was lower (p=0.003) in Group A than in Group B. We conclude that the addition of benidipine to low- or medium-dose ARB is, in light of the renal protection and the cost-effectiveness of this approach, a useful therapeutic strategy for controlling BP in hypertensive patients with albuminuria.

Benefits of candesartan on arterial and renal damage of non-diabetic hypertensive patients treated with calcium channel blockers

BACKGROUND/AIM

Although long-term, intensive blood pressure (BP) control with calcium channel blockers (CCBs) reduced arterial stiffness and renal damage of hypertensive patients, combination therapy with antihypertensive drugs is frequently needed to maintain the intensive BP control. The present study was conducted to examine add-on benefits of candesartan therapy on hypertensive patients treated with CCBs for at least 12 months.

METHODS

Pulse wave velocity (PWV), urinary albumin excretion (UAE), intima-media thickness (IMT) of the carotid arteries, and 24-hour ambulatory BP were determined in 50 non-diabetic hypertensive patients treated with CCBs before and 12 months after the start of therapy with candesartan or placebo.

RESULTS

Candesartan significantly decreased clinic BP and tended to decrease ambulatory BP, but the decreases were similar to those in the placebo group except nocturnal BP decrease, which was significantly enhanced by candesartan. Add-on candesartan significantly decreased PWV and UAE compared to placebo, but IMT was unchanged with candesartan or placebo. The decrease in clinic BP or nocturnal BP decrease did not contribute to the improvement of PWV or UAE.

CONCLUSION

Add-on candesartan functionally improved the stiffened arteries of hypertensive patients treated with CCBs by the end of 12 months of treatment independently of its effects on BPs.

Effects of combination of angiotensin receptor blocker and calcium channel blocker on ox-LDL levels and cardiovascular dysfunction in Dahl rats

In an effort to assess the cardiovascular benefits of combined angiotensin receptor blockage and calcium channel antagonism, we assessed the chronic effects of the angiotensin type 1 receptor blocker candesartan, the calcium channel blocker benidipine, and the use of a combination therapy in Dahl salt-sensitive (DS) rats. DS rats receiving a high salt diet were treated with either benidipine (4 mg/kg), candesartan (1 mg/kg) or both. Rat blood pressure was measured using a tail-cuff method. Following 12 weeks, the effect on heart weight, plasma-oxidized low-density lipoprotein (ox-LDL) level, endothelium-dependent vasorelaxation, and histology of the heart and aorta was assessed. Blood pressure, heart weight and plasma ox-LDL levels increased, while endothelium-dependent vasorelaxation decreased in the DS rats. Candesartan and benidipine inhibited the increase in blood pressure and heart weight, and the decrease in endothelium-dependent vasorelaxation. The use of benidipine alone or a combination significantly inhibited the increase in ox-LDL levels, whereas candesartan alone had no significant effect on ox-LDL levels. The present findings indicate that, if the monotherapy using ARB could not achieve adequate control of blood pressure, the combination therapy with ARB and benidipine provides the additional reductions in hypertension and cardiac hypertrophy. Moreover, the combination therapy inhibits cardiovascular dysfunction and ox-LDL levels more effectively than use of ARB alone. These results contribute to the possibility of lowering ox-LDL levels as a means of enhancing cardiovascular protection.

Calcium [corrected] channel blockers reduce angiotensin II-induced superoxide generation and inhibit lectin-like oxidized low-density lipoprotein receptor-1 expression in endothelial cells

Calcium channel blockers have been shown to limit the progression of atherosclerosis and decrease the incidence of cardiovascular events. To investigate vasoprotective effects beyond the blood pressure-lowering effects of these agents, amlodipine (10(-6) mol/) and manidipine (10(-6) mol/l) were used to pretreat angiotensin (Ang) II-stimulated rat cultured aortic endothelial cells. A 3-h period of Ang II treatment enhanced superoxide generation and the expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase protein, as detected by dihydroethidium staining and Western blotting, respectively. Pretreatment with amlodipine or manidipine attenuated the increased production of superoxide and the overexpression of NADPH oxidase. The enhanced expression of heme oxygenase-1 (HO-1) mRNA induced by Ang II was further increased by amlodipine, whereas pretreatment with manidipine led to a reduction in the expression of HO-1. Furthermore, Ang II increased vascular cell adhesion molecule-1 (VCAM-1), intracellular adhesion molecule-1 (ICAM-1), and monocyte chemoattractant protein-1 (MCP-1) mRNA levels, as determined by reverse transcription (RT)-polymerase chain reaction (PCR). Pretreatment with either amlodipine or manidipine decreased the overexpression of VCAM-1, ICAM-1, and MCP-1. We also demonstrated that amlodipine or manidipine prevented the Ang II-induced increase in lectin-like oxidized low-density lipoprotein receptor1 (LOX-1) content, thereby restoring control levels. These observations showed that amlodipine and manidipine reduced superoxide generation by the inhibition of the overexpression of NADPH oxidase in Ang II-stimulated endothelial cells. Such antioxidant effects of these agents might in turn have led to a decrease in the expression of VCAM-1, ICAM-1 and MCP-1. The salutary effects of calcium channel blockers in atherogenesis include the inhibition of the expression of LOX-1.

Comparison of the effects of cilnidipine and amlodipine on ambulatory blood pressure

Cilnidipine is a novel and unique 1,4-dydropyridine derivative calcium antagonist that exerts potent inhibitory actions not only on L-type but also on N-type voltage-dependent calcium channels. Blockade of the neural N-type calcium channel inhibits the secretion of norepinephrine from peripheral neural terminals and depresses sympathetic nervous system activity. The purpose of this study was to assess the effect of cilnidipine and amlodipine on ambulatory blood pressure (BP) levels. We performed 24-h ambulatory BP monitoring before and after once-daily use of cilnidipine (n=55) and amlodipine (n=55) in 110 hypertensive patients. Both drugs significantly reduced clinic and 24-h systolic BP (SBP) and diastolic BP (DBP) (p < 0.005). However, the reductions of 24-h (-1.19+/-6.78 vs. 1.55+/-6.13 bpm, p=0.03), daytime (-1.58+/-6.72 vs. 1.68+/-7.34 bpm, p=0.02) and nighttime (-1.19+/-5.72 vs. 1.89+/-6.56 bpm, p=0.01) pulse rate (PR) were significantly greater in the cilnidipine group than the amlodipine group. There was no correlation between the degree of daytime SBP change and that of daytime PR change after amlodipine treatment (r=-0.08, n.s.), but there was a significant negative correlation between the degree of daytime SBP change and that of day-time PR change after cilnidipine treatment (r=-0.27, p<0.05). N-type calcium channel blockade by cilnidipine may not cause reflex tachycardia, and may be useful for hypertensive treatment.

Enhanced effect of combined treatment with SMP-534 (antifibrotic agent) and losartan in diabetic nephropathy

BACKGROUND/AIMS

Diabetic nephropathy is now the most common cause of end-stage renal disease. It is also clear that the current therapy, angiotensin II blockage, cannot prevent the progression of diabetic nephropathy. We had previously demonstrated that an antifibrotic agent, SMP-534, reduced extracellular matrix production induced by transforming growth factor-beta in vitro, and that SMP-534 prevented renal fibrosis and urinary albumin in diabetic db/db mice via a nonantihypertensive mechanism. We expected that combined use of SMP-534 and losartan would produce a more highly renoprotective action.

METHODS

We examined the effects of combined treatment with SMP-534 and losartan on urinary albumin and glomerular fibrosis in db/db mice. Diet containing these agents was provided from age 9 to 25 weeks. Blood and urine analyses were performed at 8, 17, and 25 weeks. At the end of the study, kidney tissues were histologically analyzed.

RESULTS

SMP-534 significantly suppressed an increase in urinary albumin excretion and ameliorated the progression of glomerular fibrosis in db/db mice, whereas losartan did not. Combined treatment with SMP-534 and losartan markedly prevented the increase of urinary albumin excretion compared with treatment with either SMP-534 or losartan alone. In contrast, renal histological analysis revealed that combined treatment did not significantly prevent an increase of mesangial expansion in the kidney compared with treatment with SMP-534 alone.

CONCLUSION

A combination of the two agents, SMP-534 and losartan, might be a valuable therapeutic approach for the treatment of diabetic nephropathy.

Pharmacological, Pharmacokinetic, and Clinical Properties of Benidipine Hydrochloride, a Novel, Long-Acting Calcium Channel Blocker

Benidipine is a dihydropyridine-derived calcium channel blocker developed in Japan, with several unique mechanisms of action, that is, triple calcium channels (L, N, and T) blocking action with a membrane approach. Benidipine has relatively high vascular selectivity and is expected to show protective effects on vascular endothelial cells. Renal protective effects of benidipine also have been shown in several basic and clinical studies. Moreover, anti-oxidative action and enhancing nitric oxide production have been noted with this drug, following its cardio-protective effects in patients with ischemic heart diseases. In fact, benidipine exerted a better prognostic effect than other calcium channel blockers in the therapy for patients with vasospastic angina. In addition, benidipine showed reliable antihypertensive, renoprotective effects if used in combination with angiotensin II type 1 receptor blockers (ARBs) when adequate anti-hypertensive effects are not achieved by ARBs alone, indicating that benidipine is an useful calcium channel blocker in combination therapy for hypertension. Benidipine was launched on the Japanese market 14 years ago, but few severe side effects have been reported, suggesting that this is a drug with established safety and long-acting pharmacological effects.

The combination therapy of hypertension to prevent cardiovascular events (COPE) trial: rationale and design

A number of major clinical trials have demonstrated the clinical benefits of lowering blood pressure and have indicated that a majority of patients with hypertension will require more than one drug to achieve optimal blood pressure control. However, there is little data showing which antihypertensive combination best protects patients from cardiovascular events and which best achieves the target blood pressure with the fewest adverse events. The Combination Therapy of Hypertension to Prevent Cardiovascular Events (COPE) trial is the first large-scale investigator-initiated multicenter study with a prospective, randomized, open, blinded endpoint evaluation (PROBE) design to directly compare cardiovascular mortality and morbidity, incidence of adverse drug reaction, and degree of blood pressure reduction in Japanese hypertensive patients for a combination of angiotensin receptor blockers, beta-blockers or thiazide diuretics in addition to a calcium antagonist, benidipine hydrochloride, with a response-dependent dose titration scheme. The COPE trial is being conducted with the cooperation of more than 100 centers and clinics in Japan and involves 3,000 patients, who will be followed for 3 years. Eligible patients are being enrolled from May 2003 until May 2006. Results from the COPE trial should provide new evidence for selecting optimal combination therapies for hypertensive patients.

Calcium Channel Blockades Exhibit Anti-Inflammatory and Antioxidative Effects by Augmentation of Endothelial Nitric Oxide Synthase and the Inhibition of Angiotensin Converting Enzyme in the NG-Nitro-L-Arginine Methyl Ester-Induced Hypertensive Rat Aorta: Vasoprotective Effects beyond the Blood Pressure-Lowering Effects of Amlodipine and Manidipine

Long-acting dihydropyridine calcium channel blockades have been shown to limit the progression of atherosclerosis and decrease the incidence of cardiovascular events in humans and animals. To investigate the vasoprotective effects beyond the blood pressure-lowering effects of these agents, amlodipine (20 mg/kg/ day) and manidipine (10 mg/kg/day) were administered by gavage to N(G)-nitro-L-arginine methyl ester (L-NAME)-induced hypertensive rats for 2 weeks. L-NAME treatment (0.7 mg/ml in drinking water) significantly decreased the gene and protein expression of endothelial nitric oxide synthase (eNOS) and increased nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, vascular cell adhesion molecule-1 (VCAM-1), and monocyte chemoattractant protein-1 (MCP-1) mRNA levels in the aorta, as determined by Western blotting and reverse transcription (RT)-polymerase chain reaction (PCR). Amlodipine and manidipine normalized the decreased expression of eNOS gene and protein, and attenuated the overexpression of NADPH oxidase, VCAM-1, and MCP-1 mRNA. Furthermore, amlodipine and manidipine prevented the L-NAME-induced increase in the angiotensin converting enzyme (ACE) mRNA content, thereby restoring control levels in the aorta. On the other hand, hydralazine treatment had no such effect in L-NAME treated rats. Furthermore, the increased expression of manganese superoxide dismutase (Mn-SOD) by L-NAME treatment was not affected by amlodipine, manidipine, or hydralazine. We concluded that the direct anti-inflammatory and antioxidative effects of calcium channel blockades in the aorta of rats with L-NAME-induced hypertension were not likely to have been mediated by the blood pressure-lowering action of these agents, but instead these beneficial effects appear to have been mediated by an augmentation of eNOS expression and by the inhibition of the expression of ACE.

Chronic N-Acetylcysteine Administration Prevents Development of Hypertension in N.OMEGA.-Nitro-L-Arginine Methyl Ester-Treated Rats: The Role of Reactive Oxygen Species

The aim of this study was to evaluate the production of superoxide anions as well as their role in the induction and/or maintenance of high blood pressure in rats with N(omega)-nitro-L-arginine methyl ester (L-NAME)-induced hypertension. In the preventive study, we compared adult Wistar rats treated with L-NAME for 4 weeks with L-NAME-treated rats that were simultaneously given N-acetylcysteine (NAC) in their drinking water. Basal blood pressure, superoxide production, conjugated dienes concentration and NO synthase (NOS) activity were measured at the end of the experiment. Chronic NOS inhibition by L-NAME treatment increased blood pressure, enhanced superoxide production in the aorta and elevated the concentration of conjugated dienes in the heart and kidney. All these changes were prevented by simultaneous NAC administration, which augmented NOS activity in L-NAME-treated rats. In the therapeutic study, the effects of chronic NAC treatment were studied in rats with established hypertension which developed during 4 weeks of L-NAME administration. The blood pressure effects of chronic NAC treatment in established L-NAME hypertension were only moderate, although this treatment also restored NOS activity and lowered conjugated dienes in the heart and kidney. Since chronic NAC treatment had better preventive than therapeutic effects, it seems that reactive oxygen species play a more important role in the induction than in the maintenance of L-NAME hypertension.