Participação dos receptores de Ang II (AT1 e AT2) central sobre respostas cardiovasculares induzidas por salina hipertônica intragástrica em ratos com hipertensão renovascular

• Autor(a) principal: Sousa, Kássia Kristina
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• dARK ID: ark:/38995/0013000002jn9
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/9371
• topic: 2R1C; Losartan; Órgãos circunventriculares; Hiperosmolaridade plasmática; 2K1C; Circumventricular organs; Plasma hyperosmolarity; CIENCIAS BIOLOGICAS::FISIOLOGIA

The renin angiotensin aldosterone system (RAAS) is directly related to cardiovascular diseases. The effector peptide of RAAS is related to the development and maintenance of increased blood pressure (BP) is angiotensin II. Its direct action on the AT1 receptor promotes several actions that may cause the increase of BP. Thus, the present work aims to evaluate the participation of central AT1 and AT2 receptor on cardiovascular responses induced by intragastric hypertonic saline in rats with renovascular hypertension (RH). For this, Wistar rats (150-180 g) were used for the induction of HR by the model of two kidneys one clip (2K1C) with the implantation of a silver clip in the renal artery. One week after 2K1C surgery, records of systolic blood pressure (SBP) and heart rate (HR) were done for 5 weeks. Afterwards, we performed the implantation of a guide cannula in the lateral ventricle, and 5 days after, the femoral artery was cannulated, making it possible to record the cardiovascular parameters such as mean arterial pressure (MAP) and HR in agreed rats. On the following day, the animals was submmited to microinjection of saline or losartan (217 mM, 1µl) or PD123319 (40mM, 1µl) followed by intragastric hypertonic saline gavage (2 M NaCl, 2 ml) and recorded for 60 minutes. The results showed that the model was able to develop HR, in which the SBP at the first week was 142.9 ± 5.0 mmHg, p <0.05 and at the 5th week 186.3 ± 6.9 mmHg, p < 0.05, and the hypertensive animals presented hypotrophy in the clipped kidney (RD / RE = 0.709). Blockade of the central AT1 receptors did not promote blood pressure changes in normotensive animals (Δ: -0.1 ± 0.9 mmHg in relation to baseline); however, in hypertensive animals there was a reduction in blood pressure (Δ: -10.5 ± 1.9 mmHg p <0.05 compared to baseline). Hypertonic saline gavage promoted a pressure response in both normotensive and hypertensive animals, respectively (Δ: 37.9 ± 3.5 mmHg vs Δ: 37.1 ± 6.5 mmHg p <0.05; gavage) and this response was completely blocked only in RH animals after losartan (Δ: -4.4 ± 1.8 mmHg, p <0.05, 15 min after gavage). AT2 receptor blockade did not show changes in MAP. Subsequently, gavage was performed in all groups and promoted a non-sustained hypertensive effect in all of them (PD123319 normotensive Δ: 39.4 ± 4.3 mmHg, p <0.05, PD123319 hypertensive Δ: 34.0 ± 2.6 mmHg, p <0.05). Our results show that AT1 receptors present in the circunventricular organs (OCVs) are involved in the maintenance of high blood pressure in animals with renovascular hypertension and mediate cardiovascular responses induced by the intragastric 2 M hypertonic saline XIV administration in hypertensive animals, but not in normotensive animals. Thus, we may suggest that the 2K1C model can alter the pattern of angiostensinergic neurotransmission involved in responses caused by plasma hyperosmolarity.