Efeitos miocárdicos da Endotelina-1 na insuficiência cardíaca

Mestrado em Toxicologia e EcotoxicologiaA presente dissertação teve como principal objectivo esclarecer os efeitos intrínsecos da ET-1 na regulação da função miocárdica em corações saudáveis e na presença de IC induzida experimentalmente. O estudo foi levado a cabo em coelhos brancos Neo-Zelandezes saudáveis (Grupo Controlo) e com IC induzida pela doxorrubicina (1mg/kg, iv, 2 vezes por semana, durante 8 semanas; Grupo IC). A função cardíaca foi avaliada in vivo e in situ através de estudos ecocardiográficos e hemodinâmicos, respectivamente. Os efeitos miocárdicos de doses crescentes de ET-1 (0,1; 1 e 10 nM) foram avaliados in vitroem músculos papilares isolados do ventrículo direito do Grupo IC e do GrupoControlo na presença de: (i) endotélio endocárdico (EE) intacto, (ii) EE danificado, (iii) NG-Nitro-L-Arginina (L-NNA; inibidor da síntase de NO) e(iv) Indometacina (INDO; inibidor da ciclooxigénase). A avaliação ecocardiográfica e hemodinâmica demonstrou um compromissosignificativo da função ventricular dos animais do Grupo IC em comparaçãocom os do Grupo Controlo. No Grupo Controlo com EE intacto, a ET-1 promoveu efeitos inotrópicos e lusitrópicos positivos dependentes da dose.Estes efeitos mantiveram-se na ausência de EE, na presença de L-NNA e de INDO. No que respeita às propriedades diastólicas verificou-se um aumento significativo da distensibilidade miocárdica após a adição de ET-1 na presença de EE intacto. Este efeito foi abolido na ausência do EE, na presença de L-NNA ou de INDO e no Grupo IC. Demonstrou-se que a ET-1 exerce, além dos conhecidos efeitos sobre a função sistólica, um aumento da distensibilidade diastólica do miocárdio, dependente da libertação endotelial de NO e deprostaglandinas e que se encontra atenuado na IC. ABSTRACT: The main goal of the present dissertation was the study of the intrinsic effects of ET-1 in the regulation of myocardial function in healthy hearts and inexperimentally-induced heart failure. This study was carried out in healthy New Zealand white rabbits (Control Group) and diseased rabbitstreated with Doxorubicin (1mg/kg, intravenously twice a weekly for 8 weeks, DOX-HF Group). Cardiac function was evaluated in vivo and in situ by ecocardiographic and hemodynamic studies, respectively. The myocardial effects of ET-1 (0.1, 1, 10nM) were tested in vitro in papillary muscles from the DOX-HF group and from the Control Group in the presence of: (i) intact endocardial endothelium(EE); (ii) damaged EE; (iii) NG-Nitro-L-Arginine (L-NNA; NO synthase inhibitor);and (iv) Indomethacin (INDO; cyclooxigenase inhibitor). The ecocardiographic and hemodynamics studies revealed a significant impairment of the ventricular function in DOX-HF Group, in comparewith Control Group. In the presence of an intact EE, ET-1 promoted concentration-dependent positive inotropic and lusitropic effects that were maintained after damaging the EE, in the presence of L-NNA or INDO and in the DOX-HF Group. ET-1 reduced resting tension at the end of the isometric twitch(increased diastolic distensibility) in muscles with intact EE, effect that wascompletely abolished after damaging EE, in the presence of L-NNA or INDO or in the DOX-HF Group. This study demonstrated that the increase in myocardialdistensibility induced by ET-1 is absent in HF and is dependent of NO and prostaglandin release

Dual control of local blood flow by perivascular nerves and endothelial cells: changes in development, atherosclerosis and acrylamide neuropathy

This thesis examines the influence of perivascular nerves and the vascular endothelium on the local control of vascular tone with particular emphasis on how these mechanisms are affected by age and in atherosclerosis. Using the method of in vitro pharmacology, it was shown that ATP is a cotransmitter with noradrenaline (NA) in the hepatic artery of the rabbit and that the response of the vessel to the purine is mediated by ATP acting through post-junctional P2x-purinoceptors. Acetylcholine (ACh) induced a vasodilatation that was entirely dependent on the presence of an intact endothelium whereas adenosine, ATP and 2-methylthio ATP (a selective P2y-purinoceptor agonist) were shown to elicit a relaxation that was independent of the endothelium. The presence of nerve fibres containing substance P (SP), calcitonin gene-related peptide (CGRP) and vasoactive intestinal polypeptide (VIP) were demonstrated in the hepatic artery of the rabbit. Furthermore, it was shown that CGRP and VIP mediated a vasodilatation in the absence of endothelium whereas SP produced a relaxation that was endothelium-dependent. Changes in the reactivity of hepatic and saphenous arteries from male and female rabbits (2-36 months) in response to directly acting vasoconstrictor agents (NA, a, methylene ATP (a, meATP), KCl); endothelium-dependent vasodilator agents (ACh, SP); endothelium-independent vasodilator agents (CGRP, VIP, ATP) and transmural nerve stimulation are described. Male and female Watanabe Heritable Hyperlipidaemic (WHHL) rabbits (4-12 months) were used as a model for human homozygous hypercholesterolemia. After an initial reduction in endothelium-dependent vasodilatation, there was an increase in relaxation at 12 months, when plaques were present. Contractions to sympathetic nerve stimulation was also reduced at 12 months. The effects of acrylamide, which is regarded as a model for autonomic neuropathy, on the response of the hepatic, saphenous and basilar arteries are also described

Participação dos prostanóides e do cálcio na contratilidade da vesícula biliar às endotelinas

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Biológicas. Programa de Pós-Graduação em Farmacologia.O estudo avalia as ações contráteis das [endotelinas] (ETs) na [vesícula biliar] (VB) de [cobaia], comparando-as com aquelas da VB de [coelho], bem como o papel de [prostanóides] e do [cálcio intracelular] nas contrações induzidas através de receptores ETA e ETB. A ET-1 é um potente agonista contrátil da VB de coelho, que parece expressar um predomínio maior de receptores ETB sobre os ETA do que a VB de cobaia. Os prostanóides são importantes na mediação/modulação dos efeitos contráteis das ETs na VB de cobaia, pois a [indometacina] (INDO) inibe as contrações por elas induzidas, e esses peptídeos estimulam a produção de prostaciclina. As contrações tônicas induzidas pelas ETs na VB de cobaia correlacionam-se a aumentos proporcionais da concentração de cálcio intracelular livre. Os perfis inibitórios da INDO sobre as contrações e aumentos da fluorescência induzidas pelas ETs na VB de cobaia sugerem que receptores ETA e ETB sinalizam a produção de conjuntos distintos de prostanóides que exercem influências inibitórias e excitatórias na contratilidade do músculo liso, respectivamente. A relevância fisiológica e/ou fisiopatológica destes achados permanece a ser esclarecida

Beneficios de la hormona de crecimiento (GH) para el tratamiento de la isquemia de miembros inferiores: del laboratorio al escenario clínico

La isquemia crítica de miembros inferiores representa un reto para incrementar el flujo sanguíneo de la extremidad cuando fallan los tratamientos convencionales, existiendo escasas soluciones. La terapia angiogénica con factores de crecimiento y/o células madre supone una línea de tratamiento alternativo. Sin embargo, los resultados en estudios clínicos son inconsistentes. La existencia de hormonas implicadas en la angiogénesis fisiológica ha abierto una nueva línea de investigación en nuestro grupo, destinada al estudio de la hormona de crecimiento o GH para incrementar la neovascularización. En esta tesis presentamos una revisión profunda sobre el tema, y también estudios experimentales y clínicos donde se usó dicha hormona para el manejo de la isquemia periférica

Endothelin-receptor mediated responses in pulmonary resistance arteries: Effect of developmental age and left ventricular dysfunction

(1) The potent vasoconstrictor endothelin-1 (ET-1) is thought to regulate pulmonary blood flow and play a role in the aetiology of pulmonary hypertension (PHT), as well as in the transition of the pulmonary circulation from fetal to neonatal life. Responses to ET-1, and the receptor subtypes involved, were studied in isolated pulmonary resistance arteries (PRAs) from a rabbit coronary ligation model of left ventricular dysfunction (LVD), and also from fetal and neonatal rabbits. (2) The rabbit coronary ligation model of LVD displayed right ventricular hypertrophy and significant increase in lung weight in animals with coronary artery ligation for 8 weeks compared to age matched sham-operated animals. Also consistent with the development of PHT was significant structural alteration demonstrated in the pulmonary vasculature of the LVD group animals. Small muscular pulmonary arteries were studied 8, 16 and 32 weeks after coronary artery ligation or sham operation. (3) In the rabbit coronary-ligation model, investigation of ET-receptor mediated responses showed an agonist potency profile, according to pEC50 values, of SXS6c > ET-3 = ET-1 in all PRAs from all 8, 16 and 32 week procedure groups. This is indicative of a predominant role of contractile ETB receptor subtypes in these vessels, (4) ET receptor subtypes in this preparation were examined further with the use of several selective antagonists. The results demonstrated a biphasic response to ET-1 in all vessels. In sham-operated rabbit PRAs, the shallow component of the response at lower ET-1 concentrations was resistant to the effects of the non-selective ETA/ETB receptor antagonist SB209670 but sensitive to BQ788, a selective ETB receptor antagonist. The steeper component of the ET-1 response, observed at higher peptide concentrations, was resistant to BQ788 but sensitive to SB209670, These differential effects of the antagonists may provide evidence for a heterogeneous population of ETB-like-receptors. Furthermore, competition radioligand binding studies in rabbit pulmonary artery membranes provided a best fit for a two-site model, thus indicating the existence of two distinct ET receptor populations in this preparation. Ki values of 6.43 x10