RESUMEN
Human platelets possess two distinct thrombin-activated receptors, PAR-1 (protease-activated receptor-1) and PAR-4, whereas human vascular smooth muscle cells possess only PAR-1. Although such thrombin receptors have been studied extensively in vitro, their physiological roles are still rather ill-defined. We have now employed a potent, selective PAR-1 antagonist, RWJ-58259, to probe the in vivo significance of PAR-1 in thrombosis and vascular injury. RWJ-58259 was examined in two thrombosis models in guinea pigs: the arteriovenous (A-V) shunt assay (monitoring thrombus weight) and the Rose Bengal intravascular photoactivation assay (monitoring time to occlusion). Administration of RWJ-58259 (10 mg/kg, total i.v. dose) did not inhibit thrombus formation in either thrombosis model, although local, intrashunt delivery in the A-V shunt model did elicit a modest antithrombotic effect (thrombus weight reduction from 35 +/- 2 to 24 +/- 4 mg). These results are consistent with the presence of more than one thrombin-sensitive receptor on guinea pig platelets, in analogy with human platelets. Indeed, we were able to establish that guinea pig platelets express three thrombin receptors, PAR-1, PAR-3, and PAR-4. We also examined RWJ-58259 in a vascular restenosis model involving balloon angioplasty in rats. Perivascular administration of RWJ-58259 (10 mg) significantly reduced neointimal thickness (77 +/- 5 microm to 45 +/- 5 microm, P < 0.05), clearly demonstrating an important role for PAR-1 in vascular injury. From these results, it is evident that a PAR-1 antagonist is not especially effective for treating platelet-dependent thrombosis; however, it could well be beneficial for treating restenosis attendant to arterial injury.
Asunto(s)
Arterias Carótidas/efectos de los fármacos , Arterias Carótidas/metabolismo , Oclusión de Injerto Vascular/tratamiento farmacológico , Indazoles/farmacología , Agregación Plaquetaria/efectos de los fármacos , Receptores de Trombina/antagonistas & inhibidores , Urea/farmacología , Angioplastia de Balón , Animales , Arterias Carótidas/fisiología , Arterias Carótidas/cirugía , Técnicas de Cultivo de Célula , Cobayas , Humanos , Indazoles/química , Indazoles/uso terapéutico , Masculino , Agregación Plaquetaria/fisiología , Ratas , Ratas Sprague-Dawley , Receptor PAR-1 , Receptores de Trombina/fisiología , Trombosis/tratamiento farmacológico , Urea/análogos & derivados , Urea/química , Urea/uso terapéuticoRESUMEN
The antithrombotic, anticoagulant, and kinetic properties of RWJ-50353, a novel, reversible, active-site-directed thrombin inhibitor, were evaluated. RWJ-50353 inhibited the catalytic activity of human alpha-thrombin with a K(i) of 0.19+/-0.02 nM. It showed a 16-fold selectivity relative to inhibition of trypsin and at least 330-fold selectivity relative to inhibition of other biologically important serine proteases. In a gel-filtered platelet preparation, RWJ-50353 inhibited alpha-thrombin-induced aggregation with an IC(50) of 32+/-6 nM. In a canine arteriovenous shunt antithrombotic model, RWJ-50353 demonstrated a significant dose-related (0.1-1.0 mg/kg, i.v.) reduction in thrombus formation with 50% inhibition (ID(50)) obtained at 0.46+/-0.1 mg/kg. In a rabbit deep vein thrombosis model, RWJ-50353 dose-dependently (0.1-1. 0 mg/kg, i.v.) reduced thrombus formation with an ID(50) of 0.25+/-0. 03 mg/kg. The antithrombotic activity in both of these models was associated with only mild prolongations in bleeding time and coagulation parameters. These results demonstrate that RWJ-50353 is a potent, selective thrombin inhibitor that is an effective antithrombotic agent after intravenous administration in models of arterial and venous thrombosis and may be useful in the management of various thrombotic disorders.
Asunto(s)
Plaquetas/efectos de los fármacos , Fibrinolíticos/farmacología , Guanidinas/farmacología , Inhibidores de Agregación Plaquetaria/farmacología , Agregación Plaquetaria/efectos de los fármacos , Tiazoles/farmacología , Animales , Plaquetas/fisiología , Perros , Hemostáticos/farmacología , Humanos , Conejos , Trombina/antagonistas & inhibidores , Trombina/farmacologíaRESUMEN
RWJ-29009, (6S)-trans(-)-1-(6,7-dihydro-6-hydroxy-5,5-dimethyl-2-nitro-5 H-thieno[3,2-b]pyran-7-yl)-2-piperidinone, is a structurally novel and extremely potent potassium channel activator that may be useful for treatment of hypertension and ischemic heart disease. We assessed the cardiovascular profile of RWJ 29009 in anesthetized and conscious dogs. RWJ 29009 (0.1-2 micrograms/kg intravenously, i.v.) dose-relatedly increased coronary blood flow (CBF) and decreased arterial pressure in anesthetized dogs. Total peripheral resistance and coronary vascular resistance were concurrently reduced without significant changes in heart rate (HR) or cardiac output (CO). Left ventricular (LV) dP/dtmax and myocardial contractile force were decreased only at the highest dose of 10 micrograms/kg. Cromakalim (3-100 micrograms/kg), although much less potent, had a qualitatively similar profile. Glyburide pretreatment (5 mg/kg i.v.) shifted the dose response of RWJ 29009 for increasing CBF and decreasing arterial pressure to the right. The dose responses of cromakalim were similarly shifted to the right, whereas the effects of nifedipine on CBF and arterial pressure were not affected by glyburide. RWJ 29009 (0.3 and 1 microgram/kg) had no effect on myocardial O2 consumption (MVO2) except for a transient increase immediately after administration of 1 microgram/kg. MVO2 returned to control 15 min after dosing, although CBF remained significantly increased. In conscious dogs, RWJ 29009 (0.3-10 micrograms/kg, i.v. and orally, p.o.) produced dose-related increases in CBF and decreases in arterial pressure similar to those produced in anesthetized dogs, except that HR was increased concurrently. The i.v. and p.o. potency of RWJ 29009 were comparable, indicating high oral bioavailability. Thus, RWJ 29009 is an extremely potent coronary and peripheral vasodilator with a cardiovascular profile similar to that of other potassium channel activators. Like those of other potassium channel activators, its mechanism of action appears to involve activation of ATP-regulated potassium channels.
Asunto(s)
Hemodinámica/efectos de los fármacos , Piperidonas/farmacología , Canales de Potasio/efectos de los fármacos , Piranos , Tiofenos , Vasodilatadores/farmacología , Administración Oral , Anestesia , Animales , Circulación Cerebrovascular/efectos de los fármacos , Circulación Coronaria/efectos de los fármacos , Perros , Relación Dosis-Respuesta a Droga , Femenino , Frecuencia Cardíaca/efectos de los fármacos , Inyecciones Intravenosas , Masculino , Miocardio/metabolismo , Consumo de Oxígeno/efectos de los fármacos , Piperidonas/administración & dosificación , Vasodilatadores/administración & dosificaciónRESUMEN
The effects of trans-5,6-dihydro-6-hydroxy-5,5-dimethyl-2-nitro-7-(2-oxopiperidin -1-yl)-7H- thieno[3,2-b]pyran (RWJ 26629) were compared with those of the standard potassium channel opener cromakalim and several standard calcium channel blockers. RWJ 26629 lowered the mean arterial blood pressure in conscious spontaneously hypertensive (ED30 = 10 micrograms/kg p.o. or 8 micrograms/kg i.v.) and renal hypertensive (15 micrograms/kg p.o.) rats, conscious renal hypertensive (ED20 = 4 micrograms/kg p.o.) and normotensive (ED20 = 5 micrograms/kg p.o. or 2 micrograms/kg i.v.) dogs and anesthetized rhesus monkeys (ED20 = 6 micrograms/kg i.v.). RWJ 26629 was more potent than cromakalim and had a maximal activity greater than the calcium channel blockers. At antihypertensive doses, RWJ 26629 had no significant effect on cardiac force, cardiac output, stroke volume or stroke work in dogs and had little or no effect on renal, carotid or femoral blood flow or vascular resistance. RWJ 26629 was also selective for antihypertensive activity in rats compared with its ability to inhibit intestinal motility. However, RWJ 26629 did relax contracted pulmonary smooth muscle in vivo at antihypertensive doses. All compounds tested caused reflex tachycardia in conscious dogs, although this effect was lowest for RWJ 26629. Most importantly, RWJ 26629 potently and selectively increased coronary blood flow with a potency and duration of action greater than that of cromakalim or nifedipine without affecting contractile force. In vitro, RWJ 26629 selectively relaxed precontracted coronary arteries compared with its effect on femoral arteries.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Antihipertensivos/farmacología , Relajación Muscular/efectos de los fármacos , Músculo Liso Vascular/efectos de los fármacos , Canales de Potasio/efectos de los fármacos , Piranos/farmacología , Tiofenos/farmacología , Angina de Pecho/tratamiento farmacológico , Animales , Benzopiranos/farmacología , Broncoconstricción/efectos de los fármacos , Bloqueadores de los Canales de Calcio/farmacología , Cromakalim , Perros , Relación Dosis-Respuesta a Droga , Femenino , Hurones , Motilidad Gastrointestinal/efectos de los fármacos , Cobayas , Atrios Cardíacos/efectos de los fármacos , Macaca mulatta , Masculino , Ratones , Ratones Endogámicos , Músculo Liso Vascular/fisiología , Nitrendipino/metabolismo , Músculos Papilares/efectos de los fármacos , Pilocarpina/farmacología , Pirroles/farmacología , Conejos , Ratas , Ratas Endogámicas SHR , Ratas Sprague-Dawley , Rubidio/farmacocinética , Radioisótopos de Rubidio , Vasodilatadores/farmacologíaRESUMEN
The synthesis and cardiovascular evaluation of a series of isoquinolin-3-ol derivatives bearing a variety of nitrogen substituents (amino, acylamino, carbamate, and ureido) at C-4 are described. Certain of these compounds have a selective renal vasodilating profile and have minimal effects on arterial blood pressure or heart rate when administered intravenously in the instrumented anesthetized dog. The most potent renal vasodilator in the series is 4-(allylureido)-6,7-dimethoxyisoquinolin-3-ol (38), which at a dose of 1.2 mg/kg iv produces a 97% maximal increase in renal blood flow without significant hypotensive or chronotropic effects. Structure-activity observations on the nature of the 4-substituent and the alkoxy substitution pattern in the aromatic ring of the isoquinolinol nucleus are discussed.
Asunto(s)
Isoquinolinas/farmacología , Circulación Renal/efectos de los fármacos , Vasodilatadores/farmacología , Animales , Presión Sanguínea/efectos de los fármacos , Perros , Frecuencia Cardíaca/efectos de los fármacos , Relación Estructura-Actividad , Resistencia Vascular/efectos de los fármacos , Vasodilatadores/síntesis químicaRESUMEN
The oral beta-adrenoceptor blocking activity of bunolol, propanolol, and their levo-isomers was compared against isoproterenol- and treadmill exercise-induced tachycardias in normal conscious dogs. Relative potencies against isoproterenol were (ascending order): propranolol=1, levo-propranolol=2, bunolol=40, and levo-bunolol=102. Large oral doses of levo-bunolol and propranolol suppressed exercise tachycardia by only 18% (range 10 to 22%). Compared to the isoproterenol response, the tachycardia associated with severe exercise in the healthy trained dog was largely resistant to beta-receptor blockade showing factors other than beta-receptor stimulation to be involved. Differences in duration of beta-blockade were observed at equiactive doses of levo-bunolol and propranolol. The isoproterenol response had returned to greater than 50% of control by 12 hr after propranolol but was less than 10% of control at 12 hr after levo-bunolol. The time to 50% recovery of the exercise tachycardia was 24 hr after levo-bunolol and 6 to 9 hr after propranolol. The results show oral levo-bunolol to be considerably more potent and to have a longer duration of action than propranolol in inhibiting both isoproterenol and exercise-induced tachycardias in conscious dogs.