Vasoconstriction can be initiated via the interaction of a number of chemicals with specific "receptive sites" known as the receptors. This thesis examines two distinctly different modes by which drugs initiate a contractile response, namely, (i) the interaction of angiotensin analogues with a heterogeneous population of angiotensin receptors in vascular smooth muscles, and (ii) the conditions whereby B-adrenoceptor antagonists interact with a-adrenoceptor antagonists thereby causing a pressor response. Conscious, unrestrained, instrumented-rats were used for the study. It has been suggested that angiotensin receptors in vascular and non-vascular tissues may not be of a homogeneous population. The first study examined whether a heterogeneous population of angiotensin receptors was responsible for increasing vascular tone. Dose-response curves were constructed for angiotensin II (ANG II) and des Asp¹ angiotensin II (ANG III) on mean arterial pressure (MAP) and mean circulatory filling pressure (MCFP), an index of total body venous tone, in the presence or absence of [Sar¹, Ile⁸]ANG II. The i.v. infusion of ANG II or ANG III caused dose-dependent increases in MAP and MCFP. In the presence of [Sar¹, Ile⁸]ANG II, the MAP and MCFP curves for ANG II were displaced to the right with pA₂ values of 9.2 and 8.4 for the arterioles and veins, respectively. However, the antagonist displaced dose-MCFP but not the dose-MAP response curve of ANG III. This suggests that ANG II and ANG III act on the same receptor in veins but not arterioles. This concept was further investigated by obtaining dose-MAP and dose-MCFP response curves for ANG II in the presence of ANG II or ANG III. Dose-MAP response curve to ANG II was displaced to the right in the presence of ANG II but not ANG III. Dose-MCFP response curve for ANG II was displaced to the right in the presence of ANG III but not ANG II. These results again suggest that ANG III acts on the same receptors as ANG II in the veins but not arterioles. In the last series of experiments two analogues of angiotensin III were compared as antagonists of the pressor response to ANG II and ANG III. In the presence of [Ile⁷]ANG III, the dose-MAP response curves for ANG II and ANG III were displaced to the right while in the presence of [Sar¹, Ile⁷]ANG III, the dose-MAP response curve for ANG III but not ANG II was displaced. This suggests that [Sar¹, Ile⁷]ANG III is a selective antagonist of ANG III in the arterioles. In summary, the results indicate that ANG III acts on a different sub-class of angiotensin receptors than ANG II in the arterioles but it may act as a partial agonist on the same type of receptors as ANG II in the venous bed. Thus, ANG II receptors in the arterioles appear to be different from those in veins. The administration of a non-selective β-antagonist propranolol into animals subjected to non-selective α-blockade has been observed to cause a paradoxical pressor response. This second study examines whether the paradoxical pressor response to β-antagonists was due to: (i) an interaction of a β-antagonist with an α-antagonist, (ii) blockade of vasodilator β₂-adrenoceptors or (iii) an increase in the release of catecholamines. Cumulative dose-response curves for propranolol, atenolol (β₁-antagonist) and ICI 118,551 (β₂-antagonist) were obtained in rats subjected to a continuous i.v. infusion of phentolamine, a non-selective α-antagonist. The administration of each of the β-antagonists caused a dose-dependent increase in MAP suggesting that the pressor response was not due to the blockade of vasodilator β₂-adrenoceptors. Another four groups of phentolamine-treated rats were given a single i.v. bolus injection of saline, propranolol, atenolol or ICI 118,551, and sampling of arterial blood for the determination of adrenaline (A) and noradrenaline (NA) concentration by HPLC/ec. Phentolamine caused a decrease in MAP and an increase in the plasma levels of A and NA. Subsequent injection of propranolol, atenolol and ICI 118,551 but not saline increased MAP. Neither saline nor any of the β-antagonists increased plasma NA or A levels suggesting that the pressor response was not associated with an acute increase in the release of catecholamines. It was also shown that prior injection of a β-antagonist partially antagonized the hypotensive effect of phentolamine suggesting that the pressor response was related to an interaction between α- and β-antagonists. It was further shown that a continuous infusion of either prazosin or rauwolseine caused a small but not significant decrease in MAP which was reversed by propranolol. Concurrent infusions of prazosin and rauwolscine caused a large decrease in MAP. Subsequent injection of propranolol caused a large pressor response. On the contrary, sodium nitroprusside or metha-choline each decreased MAP but the hypotension was not antagonized by propranolol. These results were consistent with the existence of a specific interaction between α- and β-antagonists. These experiments demonstrated that although the mechanisms involved in the initiation of a change in vascular tone did not share a common pathway, the final outcome shared a common denomination. / Medicine, Faculty of / Anesthesiology, Pharmacology and Therapeutics, Department of / Graduate

Sandra Pavlíčková Physiological effects mediated by the brain angiotensin receptors Diploma thesis Charles University in Prague, Faculty of Pharmacy in Hradec Králové Pharmacy Department of Biological and Medical Science Supervisor: Doc.MUDr. Josef Herink, DrSc. Renin-angiotensin system (RAS) is one of the oldest and the most important hormonal systems. "Classic" angiotensin system regulates the blood pressure and homeostasis of water and electrolytes. The main bioactive peptide of this system is angiotensin II (Ang II), which, according to recent research, does not affect only one organ. Installation of the so-called "tissue" RAS, which in many cases complements "systemic" Ang II system, changes the view on RAS. It was established, that RAS components are located on other non- typical places, which cannot be incorporated to the known endocrinal function of this system. Especially, discovery of angiotensin components and receptors in brain led to formation of new hypothesis and functional concepts about local effects of RAS, based on local synthesis of Ang II and angiotensin IV (Ang IV). Current studies found that physiological effects of the central angiotensin receptors can play an important role in neuroprotection and brain perfusion, can affect stress and behavioral disorders and influence...

Orientadores: Nicola Amanda Conran Zorzetto, Fernando Ferreira Costa / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-25T23:15:59Z (GMT). No. of bitstreams: 1 Santos_AlissonFernandesdos_D.pdf: 3501020 bytes, checksum: 082754f565197f1a75d8da113de08ea3 (MD5) Previous issue date: 2014 / Resumo: A anemia falciforme (AF) é uma doença genética causada pela substituição de um ácido glutâmico por uma valina na posição 6 da cadeia globina 'beta'. A mutação de ponto origina a hemoglobina S (HbS), que sob condições de deoxigenação se polimeriza tornando os eritrócitos mais propensos à falcização. A fisiopatologia da AF resulta em processos recorrentes de vaso-oclusão e hemólise, causando numerosas complicações clínicas, incluindo a danificação dos rins e problemas cardiovasculares. A angiotensina II (Ang II), um peptídeo vasoconstritor derivado do sistema renina-angiotensina (SRA), controla a pressão arterial e o equilíbrio dos fluidos. A Ang II também participa na geração de espécies reativas de oxigênio, diminuindo a biodisponibilidade do óxido nítrico (NO), um gás vasodilatador, podendo contribuir para alterações no endotélio. A hidroxiureia (HU), agente quimioterápico importante no tratamento dos indivíduos portadores de AF, exerce seu efeito benéfico por meio do aumento de hemoglobina fetal (HbF), reduzindo a falcização dos eritrócitos, diminuindo o número de leucócitos, além de possuir a capacidade de gerar NO. O objetivo deste estudo foi verificar se a produção e expressão das proteínas do SRA estão alteradas na AF e os efeitos da terapia com HU nestes parâmetros. Para analisar a atividade do SRA na AF e um possível papel para a Ang II no processo inflamatório, foram quantificadas as concentrações plasmáticas de Ang II, enzima conversora de angiotensina (ACE), molécula de adesão vascular-1, molécula de adesão intercelular-1, endotelina-1 (ET-1), metabólitos de NO, guanosina monofosfato cíclico (GMPc), interleucina-6, interleucina-8, fator de necrose tumoral-'alfa' e inibidor do ativador do plasminogênio-1 nas amostras de sangue dos indivíduos portadores de AF e indivíduos sadios controles. A produção de Ang II e expressão de algumas proteínas do SRA também foram estudadas em um modelo animal de AF. Adicionalmente, camundongos com AF foram tratados com a HU (50 e 75 mg/kg/dia) por 4 semanas. Não foram encontradas diferenças significativas nos níveis plasmáticos de Ang II nos indivíduos portadores de AF e indivíduos controles, porém a Ang II mostrou correlação positiva com níveis plasmáticos de HbF e ET-1. Uma correlação negativa entre níveis da Ang II e GMPc também foi encontrada no plasma. As concentrações plasmáticas de ACE foram encontradas significantemente menores em indivíduos portadores de AF em comparação aos indivíduos controle. Em camundongos com AF, as concentrações plasmáticas de Ang II estão significativamente diminuídas quando comparadas aos camundongos controles. O tratamento de camundongos AF com HU (75 mg/kg/dia) aumentou significativamente os níveis de Ang II. Diferenças significativas nas expressões dos genes AT1R e ACE1 (que codificam o receptor de angiotensina II tipo 1 e a enzima ACE, respectivamente) foram detectadas em camundongos com AF sem tratamento de HU quando comparados aos camundongos controles, sendo que as expressões dos genes foram menores nos rins e maiores no fígado. Os dados obtidos no estudo sugerem que pode haver alterações no SRA em indivíduos portadores de AF, apesar de não encontrar associações entre alterações em Ang II com parâmetros inflamatórios. Futuros estudos poderiam indicar se alterações na expressão das proteínas do SRA contribuem para algumas manifestações da AF ou refletem danos teciduais nestes indivíduos / Abstract: Sickle cell disease (SCD) is caused by a point mutation that results in the substitution of glutamic acid for valine at the sixth position of the 'beta'-globin chain, leading to the production of hemoglobin S (HbS). HbS polymerizes under conditions of low oxygen concentration, causing the erythrocyte to adopt a sickled shape. The pathophysiology of SCD results in recurrent vaso-oclusion and hemolysis, causing clinicals complications, including kidney damage and cardiovascular problems. Angiotensin II (Ang II), a peptide and vasoconstrictor derived from the action of the renin-angiotensin system (RAS), controls blood pressure and fluid balance. Ang II also participates in the generation of reactive oxygen species, decreasing the bioavailability of the vasodilatory gas nitric oxide (NO), and potentially causing endothelial alterations. Hydroxyurea (HU), an important chemotherapeutic drug employed in the treatment of SCD, has numerous benefits that include augmentation of fetal hemoglobin, reduction of erythrocyte sickling and decreased leukocyte numbers; furthermore, HU also generates NO in vivo. The aim of this study was to investigate whether the production and expression of proteins of the RAS are altered in SCD and the effects of HU therapy on these parameters. To analyse alterations in Ang II and possible associations with inflamatory processes in sickle cell anemia (SCA), the following were quantified in the plasma of SCA patients on and off HU and in healthy control individuals; Ang II, angiotensin converting enzyme (ACE), vascular adhesion molecule-1, intercellular adhesion molecule-1 and endothelin-1 (ET-1), NO metabolites, cyclic guanylate monophosphate (cGMP), interleucin-6, interleucin-8, tumor necrosis factor-'alfa' and plasminogen activator inhibitor-1. The production of Ang II and the expressions of some RAS proteins were also studied in an animal model of SCD. In addition, SCD mice were treated, or not, with hydroxyurea (50 and 75 mg/kg/day) for 4 weeks. Plasma levels of Ang II of SCA patients did not differ from those of controls; however, Ang II demonstrated positive correlations with fetal hemoglobin and ET-1; and a negative correlation with plasma cGMP. Plasma levels of ACE were significantly lower in SCA individuals compared with control individuals. In SCD mice, plasma levels of Ang II were significantly decreased when compared to control mice. Treatment with HU (75 mg/kg/day) in the SCD mice increased levels of Ang II significantly. Significant differences in the gene expressions of AT1R and ACE1 (encoding the angiotensin II receptor type 1 and ACE) were detected in SCD mice not treated with HU, when compared to control mice, where these gene expressions were lower in the kidneys and higher in the liver. These results suggest that some alterations in the RAS may occur in SCD individuals. Although we found no association between plasma Ang II levels with inflammatory parameters in patients, further studies should indicate whether alterations in the RAS may contribute to some of the manifestations of SCD or reflect tissue damage in these individuals / Doutorado / Clinica Medica / Doutor em Clínica Médica