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- ItemSomente MetadadadosCALCIUM-CHANNEL BLOCKERS AS INHIBITORS OF ANGIOTENSIN I-CONVERTING ENZYME(Amer Heart Assoc, 1995-12-01) Casarini, Dulce Elena [UNIFESP]; Carmona, Adriana Karaoglanovic [UNIFESP]; Plavnik, Frida Liane [UNIFESP]; Zanella, Maria Teresa [UNIFESP]; Juliano, Luiz [UNIFESP]; Ribeiro, Artur Beltrame [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Using ion-exchange chromatography of dialyzed human urine from healthy and hypertensive patients, we detected two peaks of angiotensin I-converting enzyme (ACE) activity on hippuryl-His-Leu eluted at ionic strengths of 0.7 (F1 peak) and 1.25 (F2 peak) mS. These hydrolytic activities decreased gradually in the urine of patients submitted to isradipine treatment, F2 and F1 disappearing after 12 and 24 hours, respectively. By Western blot analysis, the urine fractions corresponding to both peaks from healthy and untreated patients presenting ACE activity and from treated patients (24 hours) without this activity were recognized by an ACE-specific antibody. These results indicated that ACE was present but inhibited in the urine of isradipine-treated patients. In vitro assays with ACE isolated from human urine and guinea pig plasma demonstrated that the enzyme is inhibited by isradipine and other commercially available calcium channel blockers, such as felodipine, nifedipine, and verapamil. A noncompetitive inhibition was observed with all calcium channel blockers studied. In conclusion, these results suggest that besides the primary effect on calcium channels, the more commonly used calcium channel blockers are also ACE inhibitors. The development of efficient calcium channel blockers with higher ACE inhibitory activity could result in interesting bifunctional antihypertensive drugs.
- ItemSomente MetadadadosCOMPARISON OF THE EFFECT OF CALCIUM WITHDRAWAL FROM THE MEDIUM AND OF BLOCKADE OF EXTRACELLULAR CALCIUM ENTRY BY ISRADIPINE ON THE CONTRACTILE RESPONSES OF THE ISOLATED RAT STOMACH(Assoc Bras Divulg Cientifica, 1991-01-01) Smaili, Soraya Soubhi [UNIFESP]; Jurkiewicz, Neide Hyppolito [UNIFESP]; Garcia, A. G.; Jurkiewicz, Aron [UNIFESP]; Universidade Federal de São Paulo (UNIFESP); UNIV AUTONOMA MADRIDThe role of calcium in drug-induced contractions of rat gastric fundus strips was evaluated by determining the effect of two procedures on the dose-response curves of agonists: a) removal of calcium from the nutrient solution and b) blockade of calcium channels with the dihydropyridine isradipine. Gastric strips were obtained from adult Wistar rats and suspended in Tyrode solution at 37-degrees-C for contraction studies. Dose-response curves for carbachol (CCh), serotonin (5-HT), KCl and BaCl2 were constructed under the two conditions described above. A complete blockade of contractile effects was observed for 5-HT and KCl 60 min after calcium withdrawal or after using 3 nM (45 min) of the calcium antagonist. A lower dose of antagonist or a shorter incubation in calcium-free solution caused a partial decrease of dose-response curves, added to a 30-fold shift to the right after the calcium antagonist (1 nM), or a larger than 100-fold shift 3 min after calcium removal. In contrast, dose-response curves for CCh and BaCl2 were not significantly affected by either type of treatment. It is concluded that 5-HT and KCl utilize extracellular sources of calcium, whereas CCh or BaCl2 depends on a tightly-bound calcium pool in this preparation.
- ItemSomente MetadadadosDecreased density of binding sites for the Ca2+ channel antagonist [3H] isradipine after denervation of rat vas deferens(Elsevier B.V., 1994-05-02) Jurkiewicz, Aron [UNIFESP]; Lafayette, Simone Sette Lopes [UNIFESP]; Nunes, S. H.; Martini, L. C.; Docarmo, LGD; Wanderley, A. G.; Jurkiewicz, N. H.; Universidade Federal de São Paulo (UNIFESP)Radioligand binding assays were performed with the selective antagonist of dihydropyridine-sensitive Ca2+ channels [H-3]PN200-110 (isradipine) in rat vas deferens, before and 7 days after denervation, and data were compared with those obtained for K+-induced contractions, which are Ca2+-dependent. the density (B-max) of dihydropyridine binding sites was decreased to almost one-third of its normal value after denervation. the respective affinity (K-D) was not significantly changed. in addition, it was observed that the K+-induced tonic contraction, which corresponded to 55 +/- 2% of the respective phasic contraction, was decreased to 41 +/- 3% after: denervation. It is assumed that the decreased density of Ca2+ channels causes a decrease in K+-induced influx of Ca2+ and consequently of the corresponding tonic contraction. These results indicate that autonomic innervation can regulate the density of dihydropyridine-sensitive Ca2+ channels in the rat vas deferens.
- ItemSomente MetadadadosISRADIPINE IN THE TREATMENT OF HYPERTENSIVE CRISIS IN AMBULATORY PATIENTS(Lippincott-raven Publ, 1992-01-01) Saragoça, Manoel Antonio da Silva [UNIFESP]; Portela, J. E.; Plavnik, Frida Liane [UNIFESP]; Ventura, R. P.; Lotaif, Leda Aparecida Daud [UNIFESP]; Ramos, Oswaldo Luiz [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)In order to investigate the efficacy of isradipine in the treatment of hypertensive crisis, we treated three groups of patients who had diastolic blood pressure (DBP) > 120 mm Hg, and who were without signs of acute target-organ damage. Isradipine was given sublingually in doses of 1.25 mg (group 1; n = 10), 2.5 mg (group 2; n = 10), and 5 mg (group 3; n = 7). Mean arterial pressure (MAP) was reduced in all patients [from 153.4 +/- 4.3 to 124.0 +/- 2.3 mm Hg at 60 min, and to 118.0 +/- 2.1 mm Hg at 2 h after administration (p < 0.001)]. The heart rate (HR) did not change significantly (from 82.4 +/- 3.7 to 84.0 +/- 6 beats/min; NS). No significant differences were noted in the overall responses of the three groups; however, blood pressure reduction was more rapid in the group receiving 5 mg compared with the other two dosages. These results show that isradipine given sublingually is effective in reducing the elevated blood pressure of a hypertensive crisis and is not accompanied by limiting side effects. Isradipine's onset of action is early (approximately 30 min after dosing) and reaches its maximum blood pressure response within 2 h of administration. No dose-dependent reductions in blood pressure were observed with the dosage range employed in this study.
- ItemSomente MetadadadosPARENTERAL ISRADIPINE REDUCES BLOOD-PRESSURE IN HYPERTENSIVE CRISIS(Elsevier B.V., 1993-03-01) Saragoça. Manoel Antonio da Silva [UNIFESP]; Mulinari, Rogerio Andrade [UNIFESP]; Oliveira, A. F.; Portela, Jorge E. [UNIFESP]; Plavnik, Frida Liane [UNIFESP]; Melegari, Diva Maria Spirandelli [UNIFESP]|Ramos, Oswaldo Luiz [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)The efficacy and tolerability of an infusion of isradipine, a calcium antagonist of the dihydropyridine type, were tested in patients in hypertensive crisis. Ten patients with symptomatic and significant elevations in blood pressure were infused for 12 h with isradipine at 1.2, 2.4, 4.8, and 7.2 mug/kg/h (3 h of each infusion level).No untoward effects or adverse reactions were noted. No alterations were observed on electrocardiographic tracings, and blood pressure was significantly reduced only at doses of 7.2 mug/kg/h.Thus, isradipine as an infusion is useful and safe for hypertensive crisis, starting at a rate of 7.2 mug/kg/h. Higher doses may yet prove to be safe, well tolerated, and even more efficacious.
- ItemSomente MetadadadosREGRESSION OF LEFT-VENTRICULAR HYPERTROPHY IN THE SHORT-TERM TREATMENT OF HYPERTENSION WITH ISRADIPINE(Elsevier B.V., 1991-02-01) Saragoça. Manoel Antonio da Silva [UNIFESP]; Portela, Jorge E. [UNIFESP]; Abreu, Patricia [UNIFESP]; Plavnik, Frida Liane [UNIFESP]; Vanneta, Adalia [UNIFESP]; Ajzen, Horacio [UNIFESP]; Ramos, Oswaldo Luiz [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)This was a study of the effectiveness of isradipine, a calcium antagonist of the dihydropyridine group, in reversing left ventricular hypertrophy (LVH) in patients with mild-to-moderate hypertension. Mean arterial pressure was effectively reduced at 90 days of treatment (from 129.5 +/- 2.0 to 111.5 +/- 2.8 mm Hg; P < .001). The electrocardiographic Romhilt-Estes score for LVH showed early reduction at 45 days of treatment (from 7.1 +/- 0.6 to 5.1 +/- 0.4 points; P < .001), and further diminutions were observed at 90 days of treatment (3.8 +/- 0.4 points; P < .01). The echocardiographically determined left ventricular mass indices confirmed these findings (from 175.0 +/- 8.9 to 141.7 +/- 5.5 and to 124.8 +/- 4.2 g/m2; P < .001) for 45 and 90 days, respectively. The results indicate that isradipine is effective in reducing left ventricular mass and that these reductions are observed early in the course of treatment.
- ItemSomente MetadadadosREVERSAL OF LEFT-VENTRICULAR HYPERTROPHY WITH ISRADIPINE INDUCES DIMINUTION OF CARDIAC-ARRHYTHMIAS(Elsevier B.V., 1993-03-01) Saragoça. Manoel Antonio da Silva [UNIFESP]; Cassiolato, Jose Luiz [UNIFESP]; Vanetta, A. M. [UNIFESP]; Canziani, Maria Eugênia Fernandes [UNIFESP]; Abreu, Patricia [UNIFESP]; Ventura, R. T. [UNIFESP]; Ramos, Oswaldo Luiz [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)The left ventricular hypertrophy (LVH) of hypertension is often associated with ventricular arrhythmias, which may increase the risk of cardiovascular mortality. Our study was therefore designed to assess whether pharmacological reversal of LVH was associated with the diminution of LV ectopic beats. The antihypertensive agent selected for the study was the dihydropyridine calcium antagonist isradipine (2.5 to 5.0 mg/day orally), which induces rapid regression of LVH.A marked temporal association was observed between regression of LV mass and reductions in the total number of ventricular extrasystoles and in paired beats. Furthermore, there was a diminution of the complexity of the form of ventricular ectopic beats during antihypertensive treatment. No changes in serum electrolytes were documented to account for this control of cardiac arrhythmias.We conclude that the reversal of LVH obtained with isradipine is accompanied by control of the ventricular arrhythmias in hypertensive patients. It is possible that this cardioprotective action may be associated non-specifically with the reduction in LV mass, although a drug- or class-specific action cannot be ruled out.