RESUMEN
A higher-throughput bioanalytical method based on fast-gradient (1 min run time) high-performance liquid chromatography (HPLC) coupled with tandem mass spectrometry (MS/MS) was developed for screen-type analyses of plasma samples from early drug discovery studies in support of exploratory pharmacodynamic studies. The HPLC system equipped with minibore column was interfaced with either atmospheric pressure chemical ionization (APCI) or electrospray (ESI) ionization techniques. The matrix ion suppression effect of both quantitative HPLC/MS/MS analyses was compared using the post-column infusion system. The use of the described methods provided advantages such as a shorter chromatographic region of ion suppression, less solvent consumption and shorter run times in comparison with standard analytical column HPLC/MS/MS methods. The analytical results obtained by both HPLC/MS/MS methods were in good agreement (within 15% of error) and displayed a good correlation with the pharmacodynamic outcome.
Asunto(s)
Preparaciones Farmacéuticas/sangre , beta-Ciclodextrinas , 2-Hidroxipropil-beta-Ciclodextrina , Animales , Cromatografía Líquida de Alta Presión , Ciclodextrinas , Haplorrinos , Espectrometría de Masas/métodos , Metilcelulosa , SolventesRESUMEN
ADP plays a critical role in modulating thrombosis and hemostasis. ADP initiates platelet aggregation by simultaneous activation of two G protein-coupled receptors, P2Y1 and P2Y12. Activation of P2Y1 activates phospholipase C and triggers shape change, while P2Y12 couples to Gi to reduce adenylyl cyclase activity. P2Y12 has been shown to be the target of the thienopyridine drugs, ticlopidine and clopidogrel. Recently, we cloned a human orphan receptor, SP1999, highly expressed in brain and platelets, which responded to ADP and had a pharmacological profile similar to that of P2Y12. To determine whether SP1999 is P2Y12, we generated SP1999-null mice. These mice appear normal, but they exhibit highly prolonged bleeding times, and their platelets aggregate poorly in responses to ADP and display a reduced sensitivity to thrombin and collagen. These platelets retain normal shape change and calcium flux in response to ADP but fail to inhibit adenylyl cyclase. In addition, oral clopidogrel does not inhibit aggregation responses to ADP in these mice. These results demonstrate that SP1999 is indeed the elusive receptor, P2Y12. Identification of the target receptor of the thienopyridine drugs affords us a better understanding of platelet function and provides tools that may lead to the discovery of more effective antithrombotic therapies.
Asunto(s)
Plaquetas/efectos de los fármacos , Fibrinolíticos/farmacología , Proteínas de la Membrana , Antagonistas del Receptor Purinérgico P2 , Ticlopidina/farmacología , Adenosina Difosfato/farmacología , Adenilil Ciclasas/metabolismo , Animales , Tiempo de Sangría , Coagulación Sanguínea , Plaquetas/metabolismo , Células Cultivadas , Clopidogrel , Marcación de Gen , Cinética , Ratones , Ratones Noqueados , Agregación Plaquetaria/efectos de los fármacos , Receptores Purinérgicos P2/genética , Receptores Purinérgicos P2Y12 , Ticlopidina/análogos & derivadosRESUMEN
The hemodynamic and platelet effects of the thrombin receptor activating peptide SFLLRN (TRAP) were evaluated in rats. TRAP failed to aggregate rat platelets in vitro (platelet rich plasma) or in vivo in the pulmonary microcirculation. In contrast, TRAP aggregated washed human platelets. Intravenous injection of TRAP (1 mg/kg) in inactin-anesthetized rats produced a biphasic response in blood pressure characterized by an initial depressor response (-25 +/- 3 mmHg for 15-30 s) followed by a pronounced pressor response (50 +/- 7 mmHg for 2-3 min). This increase in blood pressure can be attributed to increases in total peripheral resistance since cardiac output remained unchanged. Further, only the pressor responses were observed in pithed rats suggesting a direct effect of TRAP in causing smooth muscle contraction. Consequently, rat platelets differ from human platelets in that they are resistant to TRAP whereas rat vasculature is highly sensitive to TRAP. These observations suggest that while the thrombin receptors on rat vasculature may be similar to those on human platelets, the receptors and/or the coupling mechanisms in rat platelets appear different from human platelets.
Asunto(s)
Plaquetas/efectos de los fármacos , Presión Sanguínea/efectos de los fármacos , Frecuencia Cardíaca/efectos de los fármacos , Fragmentos de Péptidos/farmacología , Animales , Plaquetas/fisiología , Estado de Descerebración , Humanos , Pulmón/irrigación sanguínea , Pulmón/efectos de los fármacos , Masculino , Microcirculación/efectos de los fármacos , Agregación Plaquetaria , Ratas , Estimulación QuímicaRESUMEN
E4021 (sodium 1-[6-chloro-4-(3, 4-methylenedioxybenzyl)-aminoquinazolin-2-yl]piperidine-4-ca rboxylate sesquihydrate) is a highly selective and potent inhibitor of type V phosphodiesterase(PDE5). The in vitro and in vivo effect of E4021 on platelet function was evaluated, using echistatin, a potent disintegrin, as a positive reference agent. E4021 inhibits aggregatory response to collagen in washed human platelets (IC50 = 5 microM, vs. 0.14 microM with echistatin). In the ex vivo-platelet aggregation assay using whole blood from treated guinea pigs, E4021 (9 mg/kg i.v.) showed a moderate inhibition (43%) against collagen (0.125 microg/ml), whereas echistatin (250 microg/kg i.v.) exerted a 88% inhibition. The absence of endothelium-derived factors (NO) may account for the moderate in vitro and ex vivo antiplatelet activity of E4021. In an in vivo model of reversible platelet aggregation elicited by collagen (100 microg/kg i.v.), both E4021 and echistatin attenuated the intrapulmonary platelet accumulation in guinea pigs (-36% and -44%, respectively). In addition, E4021 (9 mg/kg i.v.) and echistatin (250 microg/kg i.v.) caused a similar inhibition of platelet adhesion at sites of microfilament-induced vascular injury in guinea pigs (52% and 65%, respectively). The two agents in combination did not show additive effect, suggesting that E4021 inhibits platelet activation and impairs interactions of adhesion receptors with matrix proteins. E4021 caused a selective increase in cGMP concentrations in the platelets isolated from treated guinea pigs: cAMP was not affected. It is concluded that the antiplatelet activity of E4021 is mediated through cGMP mechanism by virtue of selective inhibition of PDE5 in the platelets.
Asunto(s)
Inhibidores de Fosfodiesterasa/farmacología , Piperidinas/farmacología , Adhesividad Plaquetaria/efectos de los fármacos , Inhibidores de Agregación Plaquetaria/farmacología , Agregación Plaquetaria/efectos de los fármacos , Quinazolinas/farmacología , Animales , Relación Dosis-Respuesta a Droga , Cobayas , Humanos , MasculinoRESUMEN
Guinea pig platelets are similar to human platelets in their responsiveness to thrombin receptor-activating peptides and other agonists. Therefore, guinea pigs anesthetized with Inactin (90 mg/kg i.p.) were used to assess in vivo activities of thrombin and thrombin receptor-activating peptides (TRAPs) using 111 In-labeled platelets and a microcomputer-based system. The aggregatory responses are expressed as percent change for a 20 min period over basal radioactivity (AUC). Reversible accumulation of platelets occurred in the pulmonary microcirculation in response to stimuli. Human thrombin (50 and 100 U/kg i.v.) caused a dose-related platelet accumulation. Responses of similar magnitude were induced by SFLLRN (TRAP-(1-6)) and Ala-Phe(p-F)-Arg-Cha-HArg-Tyr-NH2 (high-affinity thrombin receptor-activating peptide, 0.03, 0.1 and 0.3 mg/kg i.v.). High-affinity thrombin receptor-activating peptide, a new synthetic oligopeptide agonist, is about 3-fold more potent than TRAP-(1-6), a wild-type sequence. Similarly, high-affinity thrombin receptor-activating peptide is about 4 times more potent than TRAP-(1-6) in the radioligand binding study using platelet membrane. By comparison, high-affinity thrombin receptor-activating peptide manifested an aggregatory activity (EC60 = 1.2 microM) about 15 times more potent than that of TRAP-(1-6)(EC60 = 18.6 microM) in washed guinea pig platelets. The intrapulmonary platelet aggregation in response to thrombin, TRAP-(1-6) and high-affinity thrombin receptor-activating peptide was characterized by long duration (approximately 30 min); a reduction in response (18-54%) tended to occur with repeated challenges, presumably due to desensitization and consumption. The response to thrombin (100 U/kg) was greatly inhibited by (D)-Phe-Pro-Arg-chloromethyl ketone (PPACK), a potent thrombin inhibitor (250 micrograms/kg + 6 micrograms/kg per min i.v. x 30): AUC, 150 +/- 552 vs. 7171 +/- 1052 in the control period (n = 8, P < 0.05). The response to high-affinity thrombin receptor-activating peptide (0.03 mg/kg), which acts on thrombin receptor directly, was not affected by PPACK. It is concluded that guinea pigs are an appropriate preparation for evaluation of in vivo activity of thrombin inhibitors as well as thrombin receptor agonists and antagonists.
Asunto(s)
Plaquetas/efectos de los fármacos , Fragmentos de Péptidos/farmacología , Péptidos/farmacología , Receptores de Trombina/efectos de los fármacos , Trombina/farmacología , Clorometilcetonas de Aminoácidos/farmacología , Animales , Antitrombinas/farmacología , Cobayas , Técnicas In Vitro , Radioisótopos de Indio , Pulmón/citología , Masculino , Agregación Plaquetaria/efectos de los fármacos , Ensayo de Unión Radioligante , Receptores de Trombina/agonistas , Trombina/antagonistas & inhibidoresRESUMEN
The studies reported in this article provide evidence that several complex mechanisms are involved in the ability of dopexamine HCl (DPX) in preventing ischemia-reperfusion induced organ damage. In a canine model of hemorrhagic shock in which shed-blood was reinfused, DPX prevented deterioration in renal blood flow via an action on beta-2 and DA-1 receptors, whereas its ability to preserve tubular function was essentially due its agonistic effects on DA-1 receptors. In a different experimental model in anesthetized rats, acute generation of oxygen free radicals (OFR) via intravenous administration of Xanthine (X) followed by Xanthine Oxidase (XO) resulted in depression of circulation and death of more than 80% of the animals within the observation period of 120 min. Pretreatment of the rats with DPX significantly enhanced survival rate in a dose dependent manner to about 70%. Neither dobutamine nor prenalterol, which are beta-1 adrenoceptor agonists and like DPX, potent chronotropic and inotropic agents were effective in preventing OFR induced lethal toxicity. In a separate series, a selective DA-1 receptor agonist felodopam had no protective effect and a DA-1 receptor antagonist SCH-23390 failed to antagonize the salutary effects of DPX. In contrast, salbutamol, a selective beta-2 adrenoceptor agonist significantly promoted the survival rate facilitated by DPX and a selective beta-2 adrenoceptor antagonist, ICI-558,551 significantly attenuated the survival rate. These later studies suggest that unlike in hemorrhagic shock, the beta-2 adrenoceptor agonistic properties are critical in the ability of DPX to attenuate lethal toxicity and these effects could be related to prevention of lipid peroxidation induced by oxygen free radicals.
Asunto(s)
Agonistas Adrenérgicos beta/farmacología , Agonistas de Dopamina/farmacología , Dopamina/análogos & derivados , Daño por Reperfusión/prevención & control , Superóxidos/metabolismo , Agonistas Adrenérgicos beta/administración & dosificación , Antagonistas Adrenérgicos beta/farmacología , Animales , Perros , Dopamina/administración & dosificación , Dopamina/farmacología , Agonistas de Dopamina/administración & dosificación , Antagonistas de Dopamina/farmacología , Relación Dosis-Respuesta a Droga , Hemodinámica/efectos de los fármacos , Infusiones Intravenosas , Peroxidación de Lípido/fisiología , Ratas , Ratas Sprague-Dawley , Receptores de Dopamina D1/efectos de los fármacos , Receptores de Dopamina D1/metabolismo , Insuficiencia Renal/metabolismo , Insuficiencia Renal/mortalidad , Insuficiencia Renal/prevención & control , Daño por Reperfusión/metabolismo , Daño por Reperfusión/mortalidad , Tasa de Supervivencia , Xantina , Xantinas/farmacologíaRESUMEN
SCH 51866 is a potent and selective PDE1 and PDE5 inhibitor. The antiplatelet, antiproliferative, and hemodynamic effects of SCH 51866 were compared with those of E4021, a highly selective PDE5 inhibitor. SCH 51866 inhibited PDE1 and PDE5 isozymes with a 50% inhibitory concentration (IC50) of 70 and 60 nM, respectively. SCH 51866 and E4021 inhibited washed human platelet aggregation induced by collagen with an IC50 of 10 and 4 microM, respectively, and attenuated (p < 0.05) the adhesion of 111indium-labeled platelets to the nylon filament-injured rat aorta. The doses of SCH 51866 and E4021 that inhibited platelet adhesion caused significant increases in platelet cyclic guanosine monophosphate (cGMP; p < 0.05). SCH 51866 (1-10 mg/kg, p.o. twice daily) but not E4021 (3-30 mg/kg, p.o twice daily) inhibited neointima formation in the carotid arteries of spontaneously hypertensive rats (SHRs) subjected to balloon angioplasty. Moreover, SCH 51866 (0.3-10 mg/kg, p.o.) elicited dose-dependent reduction in blood pressure in SHRs, whereas E4021 (3-30 mg/kg, p.o.) did not affect blood pressure in SHRs. In conclusion, the data suggest that inhibition of PDE1 and PDE5 isozymes by SCH 51866 exerts antiplatelet and vascular protective effects. In comparison, inhibition of PDE5 alone by E4021 exhibited antiplatelet effects without affecting neointima formation.
Asunto(s)
3',5'-GMP Cíclico Fosfodiesterasas/antagonistas & inhibidores , Plaquetas/efectos de los fármacos , Inhibidores Enzimáticos/farmacología , Hipertensión/tratamiento farmacológico , Imidazoles/farmacología , Nucleótidos Cíclicos/metabolismo , Inhibidores de Fosfodiesterasa/farmacología , Hidrolasas Diéster Fosfóricas/metabolismo , Inhibidores de Agregación Plaquetaria/farmacología , Animales , Arterias/citología , Arterias/lesiones , Arterias/fisiopatología , Plaquetas/metabolismo , Bovinos , División Celular , Fosfodiesterasas de Nucleótidos Cíclicos Tipo 5 , Perros , Humanos , Piperidinas/farmacología , Quinazolinas/farmacología , Ratas , Ratas Endogámicas SHRRESUMEN
The thrombin receptor was the first cloned G protein-coupled receptor reported to be activated by proteolytic cleavage of its extracellular amino terminus. A second proteinase-activated receptor (PAR-2) was cloned recently and expressed in Xenopus laevis oocytes. PAR-2 was activated by trypsin and by a peptide (SLIGRL) derived from the new amino terminus. Since PAR-2 mRNA was detected in highly vascularized organs, we compared the physiological functions of the thrombin receptor and PAR-2 in vascular endothelium. Thrombin and trypsin both elicited endothelium-dependent relaxations in prostaglandin F2alpha (PGF2alpha)-contracted strips of porcine coronary artery. Whereas high doses of both thrombin or trypsin (10 U/mL) caused homologous desensitization, trypsin caused further relaxation of thrombin-desensitized tissues. Thrombin and PAR-2-derived peptides (SFLLRN and SLIGRL) both induced endothelium-dependent relaxations in PGF2alpha-contracted porcine coronary arteries. SFLLRN or SLIGRL (30 micronmol/L) also showed homologous desensitization but not cross desensitization. In the presence of the NO synthase inhibitor NG-monomethyl-L-arginine (1 mmol/L), both SFLLRN- and SLIGRL-induced relaxations were partially inhibited. SFLLRN elicited weak contraction in coronary arteries without endothelium, whereas SLIGRL had no effect. Intravenous injection of SFLLRN (1 mg/kg, bolus) into anesthetized rats elicited a transient depressor response followed by pronounced pressor response. In contrast, intravenous administration of SLIGRL (1 mg/kg, bolus) produced only a marked depressor response. Consistent with the in vivo data, SFLLRN contracted the endothelium-rubbed rat aortic rings and aggregated human platelets in vitro, whereas SLIGRL had no effect. The finding that both trypsin and SLIGRL induced endothelium-dependent relaxations indicates the presence of PAR-2 on endothelial cells. In addition, both trypsin and SLIGRL elicited relaxations in thrombin- or SFLLRN-desensitized tissue, suggesting that PAR-2 is distinct from thrombin receptor in vascular endothelium. The lack of PAR-2-mediated platelet aggregation or smooth muscle contraction suggested it might not share the pathogenic properties associated with the thrombin receptor in the vasculature.
Asunto(s)
Endopeptidasas/fisiología , Endotelio Vascular/química , Receptores de Superficie Celular/fisiología , Receptores de Trombina/fisiología , Animales , Aorta Torácica/efectos de los fármacos , Presión Sanguínea/efectos de los fármacos , Vasos Coronarios/efectos de los fármacos , Humanos , Técnicas In Vitro , Masculino , Oligopéptidos/farmacología , Fragmentos de Péptidos/farmacología , Ratas , Ratas Sprague-Dawley , Receptor PAR-2 , Receptores de Superficie Celular/química , Porcinos , Trombina/farmacología , Tripsina/farmacología , Vasodilatación/efectos de los fármacosRESUMEN
Platelets have been implicated in the pathophysiology of ischemia-reperfusion injury. In this study, antiplatelet effects of cyclic GMP (cGMP)- and cyclic AMP (cAMP)-mediated agents were evaluated in renal ischemia in pentobarbital-anesthetized rats. Renal ischemia was induced by unilateral occlusion of the left renal artery (40 min) followed by reperfusion (30 min) with the contralateral kidney serving as control. 111Indium-labeled platelets, drugs or vehicle were administered 30 min before induction of renal ischemia. Occlusion of the left renal artery for 20, 40 or 60 min resulted in a 100, 300 and 600% increase (over contralateral right kidney) in the platelet-associated 111indium activity in the ischemic kidney. In all subsequent studies the kidney was occluded for 40 min to test the antiplatelet activity of individual agents. 8-Br-cGMP (0.1 and 0.3 mg/kg/min i.v.), zaprinast (0.1 mg/kg/min i.v.) and sodium nitroprusside (0.003 and 0.01 mg/kg/min i.v.) significantly attenuated platelet accumulation in renal ischemia, whereas 8-Br-cAMP (0.3 mg/kg/min i.v.) or milrinone (0.1 mg/kg i.v. bolus, plus 0.01 mg/kg/min) did not. Minoxidil (0.01 and 0.03 mg/kg/min i.v.), a vasodilator which produced equihypotensive effects as the cGMP-mediated agents, and milrinone failed to prevent platelet accumulation. These results demonstrate that modulation of the platelet function by cGMP agents can be dissociated from their blood pressure lowering effects. cGMP is known to inhibit both platelet adhesion and aggregation, whereas cAMP is only active against aggregation. The present findings provide further evidence that cGMP-mediated drugs may afford effective antiplatelet action in an in vivo model of ischemia-reperfusion injury.
Asunto(s)
Plaquetas/fisiología , AMP Cíclico/fisiología , GMP Cíclico/fisiología , Isquemia/sangre , Riñón/irrigación sanguínea , Inhibidores de Agregación Plaquetaria/farmacología , 8-Bromo Monofosfato de Adenosina Cíclica/farmacología , Animales , GMP Cíclico/análogos & derivados , GMP Cíclico/farmacología , Masculino , Nitroprusiato/farmacología , Purinonas/farmacología , Ratas , ReperfusiónRESUMEN
We have investigated both in vivo and ex vivo antiaggregatory activity of three adenosine receptor agonists in the anesthetized rabbit: the non-selective, 5'-N-ethyl-carboxamidoadenosine (NECA), the selective adenosine A1 receptor agonist, 2-chloro-N6-cyclopentyladenosine (CCPA) and the new selective A2 receptor agonist, 2-hexynyl-NECA. The drugs were administered by 30-min intravenous infusion at a dose reducing mean blood pressure by 40-50%. NECA and CCPA also markedly decreased heart rate. In ex vivo experiments, NECA (10 micrograms/kg) and 2-hexynyl-NECA (10 micrograms/kg) maximally inhibited adenosine 5'-diphosphate (ADP)-induced platelet aggregation at the end of drug infusion by 26.7 +/- 2.9% and 25.2 +/- 3.5%, respectively. In in vivo studies, the inhibition of platelet aggregation was evaluated using the technique based on selective accumulation of 111In-labeled platelets in pulmonary microcirculation upon challenge with ADP 100 micrograms/kg. NECA (10 micrograms/kg) and 2-hexynyl-NECA (10 micrograms/kg) decreased peak values for platelet accumulation by 35.3 +/- 6.9% and 52.5 +/- 5.9% and the area under curve values by 37.7 +/- 8.7% and 41.2 +/- 12.0%, respectively. In comparison, CCPA (100 micrograms/kg) did not affect platelet responses to ADP in either of the experimental models. Thus, the present study clearly demonstrates for the first time the in vivo antiplatelet activity of adenosine A2 receptor agonists, whereas the adenosine A1 receptor agonist was inactive, in consonance with the in vitro data.
Asunto(s)
Adenosina/análogos & derivados , Agregación Plaquetaria/efectos de los fármacos , Agonistas del Receptor Purinérgico P1 , Adenosina/farmacología , Adenosina Difosfato/farmacología , Adenosina-5'-(N-etilcarboxamida) , Animales , Masculino , Inhibidores de Agregación Plaquetaria/farmacología , ConejosRESUMEN
The protective effects of phosphoramidon, a dual inhibitor of endothelin-converting enzyme and neutral endopeptidase (E.C. 24.11), on renal function in ischemic acute renal failure were investigated in anesthetized rats. Intravenous infusion of phosphoramidon (0.03 and 0.1 mg/kg per min) significantly suppressed tubular sodium wasting (measured by fractional excretion of sodium) and proteinuria in the postischemic kidney without modifying functional parameters in the contralateral normal kidney. Phosphoramidon (0.1 mg/kg/min) was associated with increased glomerular filtration in the ischemic kidney. In comparison, SCH 42354, a highly selective inhibitor of neutral endopeptidase at 0.3 mg/kg/min, did not inhibit endothelin-converting enzyme or afford renal protection. The data suggest that the protective action of phosphoramidon against ischemic acute renal failure is most likely mediated by inhibition of endothelin formation.
Asunto(s)
Lesión Renal Aguda/prevención & control , Ácido Aspártico Endopeptidasas/antagonistas & inhibidores , Glicopéptidos/uso terapéutico , Neprilisina/antagonistas & inhibidores , Lesión Renal Aguda/metabolismo , Animales , Modelos Animales de Enfermedad , Enzimas Convertidoras de Endotelina , Endotelinas/metabolismo , Tasa de Filtración Glomerular , Glicopéptidos/farmacología , Infusiones Intravenosas , Masculino , Metaloendopeptidasas , Metionina/análogos & derivados , Metionina/farmacología , RatasRESUMEN
The relative importance of endothelial derived relaxing factor (EDRF)/nitric oxide (NO) in maintaining kidney function in normal condition and in acute renal failure (ARF) were evaluated in inactin anesthetized rats. ARF was induced by unilateral occlusion of the left renal artery (40 min) followed by reperfusion, with the contralateral kidney serving as normal control. This protocol resulted in marked reductions in renal plasma flow (RPF), glomerular filtration rate (GFR) and increases in fractional sodium excretion (FENa) and urinary protein excretion in the post-ischemic kidney in comparison to the contralateral normal kidney. Administration of the nitric oxide (NO) synthase inhibitor NG--monomethyl-L-arginine (0.25 mg/kg per min, L-NMMA) exacerbated the ischemia-induced changes in renal functions as reflected by further reductions in urine flow (V), GFR, marked sodium wasting and renal edema. Pretreatment of the animals with NO precursor L-arginine (2.5 mg/kg per min, L-Arg) abolished the detrimental effects of L-NMMA in ARF. In contrast, D-Arginine (2.5 mg/kg per min, D-Arg) failed to reverse the detrimental effects of L-NMMA. Infusion of L-Arg alone also resulted in improvements in RPF and GFR in the ischemic kidney. The results of the present study suggest that the function of the ischemic kidney is sustained by EDRF/NO and is thus more sensitive to NO synthase inhibition.
Asunto(s)
Lesión Renal Aguda/fisiopatología , Isquemia/fisiopatología , Riñón/irrigación sanguínea , Óxido Nítrico/antagonistas & inhibidores , Lesión Renal Aguda/patología , Animales , Arginina/análogos & derivados , Arginina/farmacología , Presión Sanguínea/efectos de los fármacos , Tasa de Filtración Glomerular/efectos de los fármacos , Masculino , Tamaño de los Órganos , Proteinuria/patología , Ratas , Daño por Reperfusión/patología , Daño por Reperfusión/fisiopatología , Sodio/orina , omega-N-MetilargininaRESUMEN
In the present studies, the efficacy of dopexamine hydrochloride, a novel DA1-receptor and beta 2-adrenoceptor agonist in preventing deterioration of cardiovascular function in a canine model of hemorrhagic shock was investigated. Pentobarbital-anesthetized dogs were allowed to bleed into a height-regulated reservoir and the hypotensive state (about 40 mmHg) was maintained for a period of 150 min. Subsequently, blood was reinfused and recoveries in various hemodynamic variables were monitored for an additional period of 120 min. Either aqueous solvent or dopexamine HCl was randomly selected for i.v. infusion beginning 30 min before reinfusion of the blood and until the termination of the experiment. In the solvent-treated control group, various cardiovascular variables such as cardiac output, stroke volume, celiac and superior mesenteric arterial blood flows progressively declined to 50% or less of the basal values; these changes were associated with sustained increases in the regional as well as systemic vascular resistances. Dopexamine infusion lowered vascular resistances and facilitated recoveries in various hemodynamic variables to 80% to 100% of the basal values after reinfusion of the shed blood. With the exception of a transient inotropic effect during reinfusion in the dopexamine treated group, there were no essential alterations in the myocardial contractility, during the hypotensive state and/or after reinfusion of the blood. Hence, the results indicate that the efficacy of dopexamine to reduce vascular resistance by actions at DA1-receptors and beta 2-adrenoceptors would account for its ability to improve myocardial performance (secondary to reductions in afterload) and restoration of mesenteric and celiac hemodynamics.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Agonistas Adrenérgicos beta/farmacología , Dopaminérgicos/farmacología , Dopamina/análogos & derivados , Corazón/efectos de los fármacos , Choque Hemorrágico/fisiopatología , Circulación Esplácnica/efectos de los fármacos , Animales , Modelos Animales de Enfermedad , Perros , Dopamina/farmacología , Hemodinámica/efectos de los fármacosRESUMEN
The common polyclad turbellarian Stylochus ellipticus is an important and abundant predator of young oysters, Crassostrea virginica, in Chesapeake Bay. Laboratory experiments revealed that higher temperature and starvation negatively affected flatworm size. Egg production, adjusted for flatworm area, was not significantly affected by flatworm size, nor by increasing number of egg batches produced. In addition, there was no significant statistical effect of higher temperature and starvation on egg production, although there were some instances of diminished egg production under these conditions. Flatworms did react to higher temperature and starvation by significantly decreasing the number of days that elapsed before egg laying began. Overall, more larvae would be produced at 21°C than at 30°C, by fed flatworms than starved flatworms, and by solitary flatworms than paired flatworms. When isolated animals were alternately fed and starved for five-week periods over a 20-week experimental period at 21°C, 56% of individuals continued to deposit eggs, although the number of eggs laid and embryo hatching success declined with time. Stylochus ellipticus individuals can maintain a relatively high reproductive effort despite reduction in available food. Thus, this species would appear to be a "capital" breeder, relying on stored energy to produce eggs.
RESUMEN
Acute renal failure was induced in pentobarbital anesthetized dogs either by withdrawal of the blood and/or by acute renal artery occlusion and efficacy of felodipine in preserving renal function was evaluated. In Wiggers' model of hemorrhagic shock, animals were allowed to bleed into a reservoir and after maintaining a hypotensive state (40-45 mm Hg) for 150 minutes, blood was reinfused and recovery in the renal function was evaluated. In a separate series, a renal artery was completely occluded for 45 minutes and after release of the occlusion recoveries in various markers of renal function were monitored. Felodipine 0.01 mumol/kg i.v. or the vehicle was administered ten minutes before hemorrhage or ten minutes prior to initiation of renal artery occlusion. Comparison of the data between the vehicle-treated dogs from the two models show that although renal blood flow (RBF) was restored to similar levels, recoveries in glomerular filtration rate (GFR), urine volume (UV), urinary excretion of sodium (UNa V) and potassium (UK V) were severely depressed in shock model (15 to 25% of the basal value) and consistently lower than the recoveries in the renal artery occlusion model (30-50%). These data could suggest that the extent of renal impairment is more severe in hemorrhagic shock. Nevertheless, felodipine pretreatment provided significant protection to renal function from ischemic damage in both the models; the drug-treated groups were characterized by significant recoveries in GFR, UNa V and UK V (60-100%) and by prompt and full restoration of RBF and UV.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Lesión Renal Aguda/prevención & control , Felodipino/farmacología , Lesión Renal Aguda/etiología , Animales , Modelos Animales de Enfermedad , Perros , Evaluación Preclínica de Medicamentos , Femenino , Tasa de Filtración Glomerular/efectos de los fármacos , Riñón/efectos de los fármacos , Riñón/fisiopatología , Masculino , Obstrucción de la Arteria Renal/complicaciones , Obstrucción de la Arteria Renal/fisiopatología , Circulación Renal/efectos de los fármacos , Choque Hemorrágico/complicaciones , Choque Hemorrágico/fisiopatologíaRESUMEN
Felodipine, a dihydropyridine calcium antagonist with potent arteriolar dilator properties, has been shown to enhance renal, mesenteric, coronary, and cerebral blood flows in intact animals as well as in man and to prevent deterioration of renal and mesenteric blood flows in Wiggers' model of hemorrhagic shock in dogs. In the present studies, efficacy of felodipine on 72 hr survival of rats subjected to an acute withdrawal of 40% of the blood volume was investigated. Shed blood was not reinfused in the present studies. Felodipine, whether administered before or after hemorrhage, facilitated dose-dependent increases in the survival rate up to 95%, whereas in the vehicle-treated group, the survival rate was 33%. Hydralazine, also an arteriolar dilator, in equi-hypotensive doses was not as effective as the calcium antagonist. Effects of felodipine are comparable to that of naloxone in enhancing survival. These data suggest that the salutary effects of felodipine can be related to its calcium antagonistic as well as arteriolar dilator properties.
Asunto(s)
Felodipino/uso terapéutico , Hidralazina/uso terapéutico , Naloxona/uso terapéutico , Choque Hemorrágico/tratamiento farmacológico , Animales , Presión Sanguínea , Volumen Sanguíneo , Venodisección , Felodipino/administración & dosificación , Frecuencia Cardíaca , Hematócrito , Hidralazina/administración & dosificación , Masculino , Naloxona/administración & dosificación , Ratas , Ratas Endogámicas , Choque Hemorrágico/mortalidad , Tasa de SupervivenciaRESUMEN
The efficacy of felodipine, a dihydropyridine calcium entry blocker to restore renal function was investigated in Wiggers model of haemorrhagic shock. Mongrel dogs were anaesthetized with sodium pentobarbital and subjected to haemorrhagic shock by allowing the animals to bleed into a reservoir. After maintaining the hypotensive state (mean blood pressure 40-45 mm Hg) for a period of 150 min, the blood was reinfused and the recovery of the various parameters were monitored for an additional 120 min. These studies were conducted in three different groups of dogs: (A) Solvent control, (B) Felodipine 0.01 mumol/kg i.v., administered 10 min prior to reinfusion of the blood, and (C) Felodipine 0.01 mumol/kg i.v., administered prior to haemorrhage. In all the three groups arterial blood pressure returned to similar basal levels following reinfusion. Felodipine administration prior to haemorrhage or before reinfusion (Group B and C) resulted in a 80-95% recovery in the renal blood flow, 60-65% in the glomerular filtration rate, 150-300% in the urine volume and 80-100% in the urinary sodium and potassium excretions. In the vehicle-treated control group, despite a 45% recovery in the renal blood flow, renal function was not restored following reinfusion. The observations made in these studies suggest that felodipine, an arteriolar dilator which also possesses natriuretic properties, could be clinically useful in the treatment of renal failure in haemorrhagic shock. Prevention of cellular calcium overload during ischaemia and reperfusion by this dihydropyridine derivative, may account for its ability to preserve vascular as well as tubular function.
Asunto(s)
Lesión Renal Aguda/tratamiento farmacológico , Bloqueadores de los Canales de Calcio/uso terapéutico , Felodipino/uso terapéutico , Choque Hemorrágico/complicaciones , Lesión Renal Aguda/etiología , Animales , Presión Sanguínea/efectos de los fármacos , Perros , Tasa de Filtración Glomerular/efectos de los fármacos , Pruebas de Función Renal , Reperfusión Miocárdica , Circulación Renal/efectos de los fármacos , Sodio/orina , Urodinámica/efectos de los fármacosRESUMEN
1. The present studies are designed to investigate whether dopexamine hydrochloride, a DA-1 receptor and beta 2-adrenoceptor agonist, is effective in preventing renal failure in Wiggers model of haemorrhagic shock in dogs. 2. Pentobarbital anaesthetized dogs were allowed to bleed into a reservoir and a hypotensive state (40-50 mmHg) was maintained for 120 min; subsequently blood was reinfused and recoveries in renal blood flow (RBF) and in various parameters reflecting renal function were monitored for an additional 150 min. 3. In the vehicle treated control group, despite a 45% recovery in the RBF, renal function was totally impaired. In the dopexamine treated groups, 80% recovery in RBF was accompanied by 60-120% recoveries in various indices of renal function such as GFR, UV, UNaV, after reinfusion of the shed blood. These salutary effects of DPX were dose dependent and were abolished by a selective DA-1 antagonist, SCH 23390. 4. These data suggest that the renal vasodilatory, natriuretic and diuretic effects of dopexamine and its ability to restore renal function after haemorrhagic shock are due to a direct action on the renal vascular and tubular DA-1 receptors. These studies demonstrate potential therapeutic usefulness of this agent in preventing renal failure.
Asunto(s)
Lesión Renal Aguda/prevención & control , Dopamina/análogos & derivados , Choque Hemorrágico/tratamiento farmacológico , Lesión Renal Aguda/etiología , Animales , Perros , Dopamina/farmacología , Femenino , Masculino , Receptores Adrenérgicos beta/efectos de los fármacos , Receptores Adrenérgicos beta/fisiología , Receptores Dopaminérgicos/efectos de los fármacos , Receptores Dopaminérgicos/fisiología , Receptores de Dopamina D1 , Circulación Renal/efectos de los fármacos , Circulación Renal/fisiología , Choque Hemorrágico/complicaciones , Choque Hemorrágico/fisiopatologíaRESUMEN
1. The influence of intra-arterial infusion of rat atrial natriuretic factor (ANF 8-33) and/or ouabain on the vascular responses to noradrenaline was investigated in the denervated and flow-controlled hindlimb preparations in pentobarbital anaesthetized dogs. 2. During the continuous infusions of ANF (30-40 min) vascular responses to noradrenaline were significantly depressed. Subsequent infusion of ouabain together with ANF (50-60 min) reversed and restored the vascular reactivity to the control levels. Hypotension produced by ANF infusion was partially reversed during the simultaneous infusions of both the agents. 3. In a separate series of experiments, in which ouabain was first infused (50-60 min) vascular responses to noradrenaline were significantly enhanced. Subsequent infusions of ANF (plus ouabain) even up to 60 min or longer failed to alter the enhanced vascular responsiveness facilitated by ouabain. 4. The present studies demonstrate a physiological antagonism between ANF and ouabain and such a phenomenon could account for the previous observation that vascular reactivity to noradrenaline was progressively enhanced after acute blood volume expansion. Whereas plasma levels of both ANF and ouabain-like inhibitor(s) of the sodium pump are elevated after volume expansion, inhibitory effects of ANF on the vascular smooth muscle may be compromised in the presence of an Na+ pump inhibitor(s).