Josefa Navarro-Cid

Endothelial dysfunction in spontaneously hypertensive rats: consequences of chronic treatment with losartan or captopril.

Background Hypertension is associated with endothelial dysfunction characterized by decreased endothelium-dependent relaxations and increased endothelium-dependent contractions. Angiotensin converting enzyme inhibitors and thromboxane A2 receptor antagonists decreased the endothelium dysfunction in hypertensive animals. Objective To investigate the effects of prolonged treatment with losartan on endothelium-dependent and -independent relaxations and contractions in aortic rings from spontaneously hypertensive rats (SHR). Materials and methods Male SHR aged 16 weeks were treated for 12 consecutive weeks either with 10 mg/kg losartan per day or with 60 mg/kg captopril per day administered via their drinking water. The systolic blood pressure was evaluated basally and during week 12. At the end of the treatment period, the vascular reactivity in aortic rings was studied. A group of rats treated with captopril was studied as a reference group. Results Losartan and captopril reduced the blood pressure significantly and comparably. Both drugs enhanced acetylcholine-induced relaxations and reduced the maximal contractile response to acetylcholine in the presence of NG-nitro-L arginine methyl ester (L-NAME). Contractile responses to phenylephrine, endothelin-I and U46619 were not affected by these treatments. Increased relaxing responses to superoxide dismutase were observed only in captopril-treated rats. Losartan reduced the contractile response to angiotensin II. By contrast, this contractile response was elevated in rats treated with captopril. Conclusions Prolonged antihypertensive treatments with losartan and captopril decreased the endothelial dysfunction in aortic rings from SHR not only by enhancing NO-dependent relaxations but also by reducing the contractions in response to an endothelium-derived contracting factor. The results further confirm that an endothelium-derived contracting factor plays a role in vascular dysfunction in SHR and the relationships between this factor and angiotensin II.

Effects of Losartan on Blood Pressure, Metabolic Alterations, and Vascular Reactivity in the Fructose-Induced Hypertensive Rat

Fructose feeding induces a moderate increase in blood pressure levels in normal rats that is associated with insulin resistance, hyperinsulinemia, and hypertriglyceridemia. The sympathetic nervous system seems to participate in the alterations of this model. To further explore the mechanisms underlying fructose-induced hypertension, the effects of the AT1 receptor antagonist losartan on blood pressure, insulin resistance, renal function, and vascular reactivity in mesenteric vascular beds were studied. Sprague-Dawley rats were fed for 4 weeks with diets containing 60% fructose or 60% starch (control), and half of each group received losartan (1 mg/kg per day) in the drinking water. Fructose-fed rats showed higher (P < .05) blood pressure levels and plasma concentrations of triglycerides and insulin than those of controls. Losartan treatment prevented both blood pressure elevation and hyperinsulinemia in fructose-fed rats but not elevation of plasma triglycerides. Plasma glucose and insulin levels in response to an oral glucose load were higher (P < .05) in fructose-fed rats than in controls. These exaggerated responses were prevented by losartan treatment. No differences in the constrictor responses of mesenteric vascular beds to KCl (60 mumol), angiotensin II (1 nmol), phenylephrine (10(-5) mol/L), or endothelin-1 (10 pmol) were found between the two groups. Relaxing responses to acetylcholine or sodium nitroprusside in phenylephrine-precontracted mesenteric vascular beds and constrictor response to the nitric oxide synthesis inhibitor NG-nitro-L-arginine methyl ester (100 nmol) were comparable in both groups. Losartan blunted angiotensin II constriction and reduced (P < .05) responses to phenylephrine in all groups.(ABSTRACT TRUNCATED AT 250 WORDS)

AT1 Receptor Antagonism Reduces Endothelial Dysfunction and Intimal Thickening in Atherosclerotic Rabbits

The effects of angiotensin (AT)(1) receptor antagonists on functional and morphological alterations associated with atherosclerosis are not well known. The current study was performed to examine the long-term effects of valsartan (3 or 10 mg/kg per day for 10 weeks) on endothelial function and structural changes in aorta from rabbits fed with either a control diet or a cholesterol-enriched diet. Rabbits fed with the cholesterol-rich diet showed higher (P<0.05) plasma levels of cholesterol than did controls. Treatment with valsartan (3 or 10 mg/kg per day) did not alter plasma cholesterol levels or systolic arterial pressure in any group. Contractions induced by angiotensin II were comparable in both control and hypercholesterolemic rabbits and were markedly reduced by treatment with valsartan. Relaxations induced by acetylcholine were lower in hypercholesterolemic rabbits than in controls. Treatment with valsartan (3 or 10 mg/kg per day) enhanced (P<0.05) this response in hypercholesterolemic rabbits but not in controls. Lumen and media cross-sectional areas were comparable in control and hypercholesterolemic rabbits. Vessel area was higher (P<0.05) in hypercholesterolemic rabbits than in controls. Intimal lesion was 29.5+/-6% in cholesterol-fed rabbits and nonexistent in control rabbits. Treatments with 3 and 10 mg/kg per day valsartan reduced (P<0.05) intimal lesion to 2.4+/-0.7% and 2.7+/-0.9%, respectively, and increased lumen area in hypercholesterolemic rabbits. No changes in either vessel or media cross-sectional areas were observed in these animals. In summary, angiotensin II, through AT(1) receptors, appears to play a key role in the development of the vascular functional and structural changes associated with hypercholesterolemia. AT(1) receptor antagonists, besides their antihypertensive effects, could be an important therapeutic tool to reduce the development of atherosclerosis.

Renal and Vascular Consequences of the Chronic Nitric Oxide Synthase Inhibition Effects of Antihypertensive Drugs

The effects of the administration of either the angiotensin converting enzyme (ACE) inhibitor, quinapril (10 mg/kg/day, orally), or the calcium antagonist, diltiazem (100 mg/kg/day, orally), on blood pressure (BP), renal function, and vascular reactivity in isolated perfused mesenteric beds were studied in rats treated for 8 weeks with the nitric oxide (NO) synthesis inhibitor, NG-nitro-L-arginine methyl ester (LNAME, 40 mg/kg/day). The oral administration of LNAME significantly increased systolic BP values, which reached the levels of 186 +/- 7 mm Hg at week 8. Both quinapril and diltiazem reduced this, although the ACE inhibitor was more effective than the calcium antagonist. The chronic inhibition of NO resulted in an increase in water excretion whether or not the increase in systolic BP was prevented by the coadministration of either quinapril or diltiazem. At the end of the experiment, LNAME-treated rats presented higher proteinuria than control rats (140 +/- 4 mg/24 hours v 21 +/- 1 mg/24 hours, P < .05). This elevated protein excretion was normalized by both antihypertensive drugs. None of the treatments was able to modify either natriuresis or plasma creatinine levels. Endothelium-dependent relaxations to acetylcholine (10(-12) to 10(-8) mol/L) were comparable in all groups. However, the vasoconstriction induced by either the continuous infusion of phenylephrine (10(-5) mol/L) or by a bolus of angiotensin II (1 nmol) was higher in the animals that received LNAME than in control ones. The antihypertensive therapy normalized the response to phenylephrine but not to angiotensin II. These data suggest that both quinapril and diltiazem are not only able to reduce BP elevation induced by the chronic administration of LNAME in rats, but also to prevent the renal damage and the hyperresponsiveness to phenylephrine induced by this NO synthesis inhibitor.

Antihypertensive efficacy and tolerability of Lercanidipine in daily clinical practice. The ELYPSE study

Aim : Lercanidipine, a long-acting dihydropyridine with a good antihypertensive efficacy and tolerability in clinical use. With the aim to determine the efficacy and tolerability of this drug in usual clinical practice we performed the ELYPSE trial. Methods : Grade 1 or 2 essential hypertensive patients in whom their physicians considered to prescribe a dihydropyridine were conferred to Lercanidipine 10 mg once daily with a 3-month follow-up; 9059 patients were included (age: 63 - 11 years; 58% women, 60% over 60 years, 56% grade 2 hypertensives and 69% previously treated with other antihypertensive drugs). A subgroup of 1267 patients (14%) who were included in the study had experienced adverse reactions with other drugs. Electronic case-report forms and a central database (Internet) were used in this trial. Results : At baseline, blood pressure (BP) was 160.1 - 10.2/95.6 - 6.6 mmHg; and heart rate (HR) 77.3 - 9.3 beats/min. Significant reductions in both systolic and diastolic BP were attained at 1 month with slight additional decreases 2 months later. At 3 months, BP was 141.4 - 11.3/83.1 - 6.9 mmHg, and HR 75.2 - 8.2 beats/min ( p < 0.001 versus baseline). At the study end, 64% of the patients achieved a diastolic BP <90 mmHg, BP control (< 140/90 mmHg) was attained in 32%. In the subgroup of diabetics ( n = 1269) an adequate BP control (lt;130/85) was attained in only 16.4%. The overall incidence of adverse events was 6.5%, of which the most frequent were headache (2.9%), ankle oedema (1.2%), flushing (1.1%) and palpitations (0.6%). Withdrawal rate was < 1%. The efficacy and tolerability in the subgroup of patients included in the study due to adverse events with other drugs were similar to the whole study group. Conclusion : In this study Lercanidipine has shown a good efficacy and tolerability in daily clinical practice. These findings are concordant with those reported in randomized controlled trials. 130/85) was attained in only 16.4%.

Losartan reduces constrictor responses to endothelin-1 and the thromboxane A2 analogue in aortic rings from spontaneously hypertensive rats: role of nitric oxide.

Objective Our study was designed to investigate whether angiotensin II subtype 1 (AT1) receptors are involved in the constrictor responses evoked by endothelin-1 and the thromboxane A2 analogue U46619 in aortic rings from spontaneously hypertensive rats (SHR), by studying the effect of the AT1 receptor antagonist losartan. In addition, since nitric oxide seems to participate in the mechanism of action of losartan, we studied the effect of the nitric oxide synthesis inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), on the action of losartan. Materials and methods Dose-response curves of either endothelin-1 (10−10 to 10−7 mol/l) or U46619 (10−10 to 10−6 mol/l) were studied in the presence or absence of losartan (10-5 mol/l) in aortic rings from SHR. Likewise, similar experiments were done in aortic rings pretreated with the nitric oxide synthesis inhibitor, L-NAME (10−4 mol/l). Results Pre-incubation with losartan significantly reduced the contractile response to endothelin-1 compared with control rings, without modifying the value represented by 50% of the maximal response (pD2). The concentration-response curve to U46619 was shifted to the right in the presence of losartan, reducing the pD2 compared with control rings. The presence of captopril (10-5 mol/l) in the incubation media did not alter the response to either endothelin-1 or U46619. The diminished response to both endothelin-1 and U46619 in the presence of losartan was reversed in L-NAME-pretreated rings. Conclusions Angiotensin II seems to participate in the vasoconstriction induced by both endothelin-1 and the thromboxane A2 analogue through the stimulation of AT1 receptors in SHR aortic rings, because losartan inhibited this effect. Moreover, nitric oxide appears to be involved in this action of losartan.

Relevance of endothelium-derived hyperpolarizing factor in the effects of hypertension on rat coronary relaxations.

Objectives To evaluate the relative participation of nitric oxide (NO), endothelium-derived hyperpolarizing factor (EDHF) and prostanoids in the relaxing responses induced by acetylcholine and isoproterenol in isolated coronary arteries from adult Wistar–Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). Design and methods Male adult WKY rats and SHR were used in the study. Segments from left coronary arteries (approximately 350–380 μm internal diameter and 2 mm long) were mounted in an isometric myograph and pre-contracted with serotonin. Dose–response curves to acetylcholine and isoproterenol were carried out in absence and presence of the NO synthesis inhibitor NG-nitro-l-arginine methyl ester (lNAME), the inhibitor of the cyclo-oxygenase, indomethacin and KCl. Areas under the respective dose–response curves were used to calculate the approximate relative participation of NO, EDHF and prostanoids. Results Relaxations to either acetylcholine or isoproterenol were lower in SHR than in WKY rats. In WKY rats, presence of lNAME diminished (P < 0.05) relaxation to acetylcholine from 10−9 to 10−6 mol/l, and induced a contracting response at 10−5 and 10−4 mol/l of acetylcholine. Addition of indomethacin did not significantly affect dose-related relaxation to acetylcholine 10−9 to 10−6 mol/l in WKY rats, and reduced (P < 0.05) the contracting response observed at 10−5 mol/l of acetylcholine. In SHR, addition of lNAME markedly reduced (P < 0.05) acetylcholine relaxations, but did not produce any contracting effect. Addition of indomethacin on top of lNAME slightly (P < 0.05) enhanced relaxing response to acetylcholine in SHR. Presence of lNAME in the media diminished (P < 0.05) relaxation to isoproterenol in both WKY rats and SHR. Addition of indomethacin on top of lNAME increased (P < 0.05) isoproterenol-relaxing response to levels similar to and higher than control conditions in WKY rats and SHR, respectively. Addition of KCl blunted both acetylcholine- and isoproterenol-relaxations in both groups. Conclusions NO and EDHF are the main endothelium-derived relaxing factors underlying acetylcholine and isoproterenol relaxations in rat coronary arteries, respectively. EDHF reduction, and not only NO reduction play a key role in the diminished coronary relaxations induced by acetylcholine and isoproterenol in SHR. An arachidonic acid derivative with contracting activity released by acetylcholine and isoproterenol in a differential manner, could oppose the relaxing actions of NO and EDHF.

Effects of antihypertensive therapy on factors mediating endothelium-dependent relaxation in rats treated chronically with L-NAME.

OBJECTIVES To evaluate the relative participation of endothelium-derived factors mediating relaxation in response to acetylcholine in isolated mesenteric vascular beds from rats treated chronically with N(G)-nitro-L-arginine methylester (L-NAME); and to compare the consequences of prolonged treatment with either an angiotensin converting enzyme inhibitor or a calcium channel blocker on the components of acetylcholine-induced relaxation in this vascular preparation. MATERIALS AND METHODS Male Sprague- Dawley rats were treated for 8 weeks with L-NAME (40 mg/kg per day), quinapril (10 mg/kg per day), diltiazem (100 mg/kg per day), L-NAME + quinapril and L-NAME + diltiazem. Systolic blood pressure was estimated by a tail-cuff plethysmograph. Relaxing responses to acetylcholine (10(-12) to 10(-8) mol) in mesenteric vascular beds precontracted with phenylephrine (10(-5) mol/l) were studied in the presence and absence of L-NAME (10(-5) mol/l), L-NAME + indomethacin (10(-5) mol/l) or L-NAME + indomethacin + potassium chloride (6 x 10(-5) mol/l). The area under the dose- response curve was used to calculate the approximate participation of nitric oxide, prostaglandins or endothelium-derived hyperpolarizing factor in the acetylcholine-induced relaxation. RESULTS Chronic administration of L-NAME increased blood pressure levels and vascular responsiveness to phenylephrine. Treatments with either quinapril or diltiazem reduced blood pressure levels and attenuated the increased response to phenylephrine. Relaxing responses to acetylcholine were similar in all groups, independently of the treatment received. The calculated participation of endothelium-derived hyperpolarizing factor in the acetylcholine-induced relaxation was higher than that of nitric oxide and prostaglandins in all groups, but was higher in L-NAME-treated than in untreated rats. In contrast, the participation of both nitric oxide and prostaglandins was higher in control than in L-NAME-treated rats. Quinapril increased the participation of prostaglandins in L-NAME-treated rats. Diltiazem increased the participation of nitric oxide in L-NAME-treated rats. CONCLUSIONS The administration of L-NAME in Sprague-Dawley rats increased the production of endothelium-derived hyperpolarizing factor as a compensatory mechanism to maintain acetylcholine-induced relaxation. Antihypertensive therapy with either quinapril or diltiazem produced a selective redistribution of the endothelial factors mediating acetylcholine-induced relaxation.

Chronic treatment with losartan ameliorates vascular dysfunction induced by aging in spontaneously hypertensive rats.

Objective To evaluate the effects of prolonged treatment with losartan on endothelium-dependent and endothelium-independent relaxations of aortic rings from adult and senescent spontaneously hypertensive rats, and to clarify whether these effects were due to specific mechanisms of the drug or a consequence of its blood-pressure-lowering action. Materials and methods Adult (aged 5 months) and senescent (aged 20 months) male spontaneously hypertensive rats were treated for 12 consecutive weeks with 10 mg/kg per day losartan. Systolic blood pressure and plasma concentration of nitrates were evaluated. We studied endothelium-dependent and endothelium-independent relaxations and response to angiotensin II of aortic rings from rats of each group. The direct effects of angiotensin II type 1 receptor antagonism on vascular reactivity of aortic rings from untreated adult and senescent rats that had been incubated beforehand with losartan were also studied. Results Losartan treatment comparably reduced blood pressure and increased plasma concentration of nitrates in rats of both age groups. Responses to acetylcholine and sodium nitroprusside were lower for rings from senescent than they were for rings from adult rats. Constrictor responses to angiotensin II were higher for rings from senescent than they were for rings from adult rats. Treatment with losartan increased the magnitude of relaxations in response to acetylcholine for rings from rats in both groups, but increased the magnitude of relaxations in response to nitroprusside only for rings from senescent spontaneously hypertensive rats. Incubation beforehand of aortic rings from untreated rats with losartan enhanced magnitude of relaxations in response both to acetylcholine and to nitroprusside only for rings from senescent spontaneously hypertensive rats. Conclusions The consequences of aging for endothelium-dependent and endothelium-independent relaxations of rings from spontaneously hypertensive rats are ameliorated by losartan treatment, suggesting that angiotensin II plays a role via type 1 receptors. The effects of losartan on senescent spontaneously hypertensive rats were due not only to its blood-pressure-lowering action but also to the blockade of specific mechanisms derived from angiotensin II type 1 receptor antagonism, which might involve an increase in availability of NO. J Hypertens 16:665–672

N-acetylcysteine potentiates the antihypertensive effect of ACE inhibitors in hypertensive patients.

Sulfhydryl group donors, such as N -acetylcysteine (NAC), may enhance the antihypertensive effect of some drugs through a nitric oxide (NO) mechanism. It has been observed that the hypotensive effect of angiotensin-converting enzyme inhibitors (ACEIs) is, at least partially, mediated by NO. We performed a within patient crossover study with the aim to investigate the potential effect of NAC on the ACEI antihypertensive action, via an NO-dependent mechanism. We studied 18 smoker (> 10 years of habit and > 10 cigarettes daily) hypertensive patients (15 males and three females, aged 69 - 5 years) on ACEI therapy (11 captopril and seven enalapril). Patients were randomly allocated to two treatment arms. In one arm, the patients ( n = 10) initially received the addition of NAC (600 mg t.i.d.) to the ACEI regimen. In the other group ( n = 8), the patients remained only on ACEI. After 21 days, the therapeutic patterns were crossed. The first group received only ACEI, and the second group received ACEI and NAC and completed other 21-day treatment period. We evaluate the effect of NAC on each patient by ambulatory blood pressure monitoring (ABPM), performed at the end of each therapeutic regimen. A significant decrease in systolic and diastolic 24-h blood pressure (24 hBP) and daytime BP (dtBP) was achieved with the combination of ACEI and NAC (ACEI + NAC) when compared to the period with only ACEI: 24 hBP = 146.1 - 4.2 vs 137 - 3.1 ( p < 0.05) and 89.2 - 2.8 vs 83.5 - 3.7 mmHg ( p = 0.01). DtBP: 149.7 - 5.6 vs 141 - 3.7 and 92.1 - 4 vs 86 - 3.2 (both, p < 0.05). No significant difference was observed in night-time BP (ntBP). The NAC effect was not statistically different for the two ACEIs. In conclusion, the addition of NAC to an ACEI potentiates its antihypertensive effect during 24hBP and dtBP in smoker hypertensives. This effect may be mediated by an NO-dependent mechanism, probably through the protective effect of NAC on NO oxidation.