RESUMO
The perfusion of serum, citrated whole blood and citrated plasma, through a simple tube system resulted in a significant loss of large von Willebrand factor (vWf) multimers, without decrease in antigen levels. Maximum loss of large multimers was observed at a shear rate of 15,000 s-1 for 15 min. Heparin, aprotinin, soybean trypsin inhibitor, phenylmethylsulphonylfluoride, N-ethylmaleimide, leupeptin or calpain inhibitor peptide could not prevent the loss of large vWf multimers in citrated plasma. The addition of EDTA calcium salt partially prevented it, and it was totally prevented by EDTA without calcium. Perfusion of purified vWf did not induce the loss of large multimers, but this did happen after the addition of either whole serum or a plasma fraction. The activity of this plasma fraction disappeared at pH < 6.8. Besides, we have found that the binding to subendothelium of purified vWf diluted in dialyzed serum was lower at pH 7.2 than at pH 6.0. Chromatographic studies demonstrated that the loss of large vWf multimers, induced by high shear rates, involves a plasma substance(s) of molecular weight larger than 200 kD; calpain and granulocyte or cysteine proteases do not seem to be this plasma substance(s).
Assuntos
Perfusão/métodos , Plasma/química , Fator de von Willebrand/análise , Fator de von Willebrand/isolamento & purificação , Técnicas In VitroRESUMO
In this study we have investigated the effect of human mononuclear leukocytes (ML) on platelet aggregation. The results obtained demonstrated that coincubation of platelets with nonstimulated ML decreased platelet aggregation induced by collagen or thrombin in a concentration-dependent manner. The inhibitory effect increased with the incubation period of the cells, reaching a plateau at 5 minutes. T and non-T enriched ML suspensions exerted an inhibitory effect similar to the total population of ML. Supernatants from ML or mixed cell suspensions also diminished platelet aggregation. 6-keto PGF1 alpha concentration in the supernatants was less than 10 pg/ml. Hemoglobin, L-arginine and cytochrome C did not modify the antiaggregating activity of ML, whereas superoxide dismutase potentiated the inhibition of aggregation mediated by ML. The inhibitory effect was not modified by monoclonal antibody (MoAb) against the lymphocyte function-associated antigen 1, alpha subunit (LFA-1 alpha) or by a MoAb directed against P-selectin. Our results demonstrated that ML inhibited platelet aggregation, at least partially, by the release of a soluble factor(s) distinct of prostacyclin or nitric oxide. Surface adhesion molecules seem also not to be involved.
Assuntos
Leucócitos Mononucleares/fisiologia , Agregação Plaquetária , 6-Cetoprostaglandina F1 alfa/farmacologia , Anticorpos Monoclonais/farmacologia , Arginina/farmacologia , Colágeno/farmacologia , Meios de Cultivo Condicionados/farmacologia , Grupo dos Citocromos c/farmacologia , Fibrinogênio/farmacologia , Hemoglobinas/farmacologia , Humanos , Antígeno-1 Associado à Função Linfocitária/imunologia , Subpopulações de Linfócitos/fisiologia , Monócitos/fisiologia , Selectina-P , Agregação Plaquetária/efeitos dos fármacos , Glicoproteínas da Membrana de Plaquetas/antagonistas & inibidores , Glicoproteínas da Membrana de Plaquetas/imunologia , Superóxido Dismutase/farmacologia , Trombina/farmacologiaRESUMO
Human polymorphonuclear leucocytes (PMN) stimulated with either immune complexes (IC), phorbol myristate acetate (PMA) or N-formyl-methionyl-leucyl-phenylalanine (FMLP) generate platelet-activating factor (PAF-acether). The present study demonstrates that treatment of PMN with recombinant human interferon-gamma (IFN-gamma) significantly enhanced the production of PAF-acether by stimulated cells, in a concentration-dependent mode. On the contrary, alpha and beta IFN were completely unable to increase PAF-acether synthesis by stimulated PMN. The significance of these results is discussed.
Assuntos
Interferon gama/farmacologia , Neutrófilos/metabolismo , Fator de Ativação de Plaquetas/biossíntese , Complexo Antígeno-Anticorpo/fisiologia , Células Cultivadas , Humanos , N-Formilmetionina Leucil-Fenilalanina/farmacologia , Neutrófilos/efeitos dos fármacos , Acetato de Tetradecanoilforbol/farmacologiaRESUMO
1. The effect of unstimulated human polymorphonuclear leukocytes (PMNs) on platelet activation was examined. 2. Human platelet aggregation and adenosine 5'-triphosphate (ATP) release induced by collagen (1-2 micrograms ml-1); thrombin (0.01-0.02 u ml-1) or arachidonic acid (AA) (0.1-0.2 mM) were markedly inhibited when conducted in the presence of unstimulated PMNs. 3. Platelet inhibition induced by PMNs was dependent on the number of PMNs and on the incubation time of the mixed cell suspension. 4. Platelet inhibition was not reversed in time when PMNs were depleted from the mixed-cell suspension. 5. PMN-mediated platelet-inhibition was not mediated by AA metabolites, oxygen reactive intermediates, nitric oxide or proteases. 6. The factor(s) accounting for the platelet inhibition mediated by PMNs are not yet characterized.
Assuntos
Neutrófilos/fisiologia , Ativação Plaquetária/fisiologia , Trifosfato de Adenosina/sangue , Humanos , Técnicas In Vitro , Agregação Plaquetária/efeitos dos fármacos , Agregação Plaquetária/fisiologiaRESUMO
BAS is a protein generated by aortic rings isolated from rats. Our previous results clearly established that BAS inhibits platelet aggregation and modifies vascular tone. We have now examined the effect of separated segments of thoracic aorta and the effect of sex on the release of the BAS and PGI2. We evaluated three different segments of thoracic aorta: A = aortic arch, B = the upper segment and C = the lowest segment of the thoracic aorta. We measured the release of BAS and PGI2 from them. The BAS production increased in the first segment (A) when compared with the other two (B and C), whilst PGI2 production was the same along the thoracic aorta. On the other hand female and male thoracic aorta produced the same levels of BAS and 6-keto PGF1 cm.
Assuntos
Aorta Torácica/metabolismo , Epoprostenol/biossíntese , Inibidores da Agregação Plaquetária/metabolismo , Biossíntese de Proteínas , Animais , Feminino , Humanos , Técnicas In Vitro , Masculino , Ratos , Ratos Endogâmicos , Fatores SexuaisRESUMO
Se estudiaron siete pacientes con tromboastenia de Glanzmann. Se realizó agregación plaquetaria con reacción de liberación en un agregómetro Lumi. No se observó agregación con ADP, adrenalina o colágeno. El ácido araquidónico indujo una agregación de sólo 14,9%. Con ristocetina y con factor VIII bovino la aglutinación fue marcadamente disminuida. La liberación de ATP estuvo ausente con todos los agentes agregantes excepto con ácido araquidónico que provocó una liberación normal. Se realizó curva dosis respuesta con análogo de PGH2. Con dosis de 1 micronM a 100 micronM sólo se obtuvo una mínima agregación mientras que la liberación de ATP fue normal. Los resultados confirmarían la independencia de los mecanismos de agregación y liberación. La liberación de ATP inducida por ácido araquidónico o análogo de endoperóxido no parece requerir la exposición y fijación del fibrinógeno a su receptor
Assuntos
Pré-Escolar , Criança , Adulto , Humanos , Masculino , Feminino , Retração do Coágulo , Agregação Plaquetária , Trombastenia/sangue , Ácidos Araquidônicos/metabolismo , Difosfato de Adenosina/metabolismo , Trifosfato de Adenosina/metabolismo , Trombastenia/fisiopatologia , Tromboxanos/metabolismoRESUMO
Se estudiaron siete pacientes con tromboastenia de Glanzmann. Se realizó agregación plaquetaria con reacción de liberación en un agregómetro Lumi. No se observó agregación con ADP, adrenalina o colágeno. El ácido araquidónico indujo una agregación de sólo 14,9%. Con ristocetina y con factor VIII bovino la aglutinación fue marcadamente disminuida. La liberación de ATP estuvo ausente con todos los agentes agregantes excepto con ácido araquidónico que provocó una liberación normal. Se realizó curva dosis respuesta con análogo de PGH2. Con dosis de 1 micronM a 100 micronM sólo se obtuvo una mínima agregación mientras que la liberación de ATP fue normal. Los resultados confirmarían la independencia de los mecanismos de agregación y liberación. La liberación de ATP inducida por ácido araquidónico o análogo de endoperóxido no parece requerir la exposición y fijación del fibrinógeno a su receptor (AU)