Effects of Physical Activity of Varied Intensities in Renovascular Hypertension 2k1c rats / EFEITOS DA ATIVIDADE FÍSICA DE INTENSIDADES VARIADAS EM RATOS COM HIPERTENSÃO RENOVASCULAR 2R1C

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

IX In hypertension, caudal ventrolateral medulla neurons (CVLM) are unable to counteract the increased intrinsic activity of rostral ventrolateral medulla neurons. Besides, the increased activity of renin angiotensin system (RAS) represents an important humoral change that promotes hypertension, raising the sympathetic vasomotor tonus and impairing the baroreflex sensibility. Physical activity of low and moderate intensity has been used associated to a pharmacological treatment as a non pharmacological treatment, reducing or restoring the alterations promoted by the high arterial pressure level (AP). The present study aimed to evaluate the contribution of swimming, with or without load, in different cardiovascular parameters in a rat model of hypertension 2 kidney 1 clip (2K1C). Male Fisher rats (9 to 11 weeks), weighing 150 to 200 g, were used. The surgeries (SHAM or 2K1C) were performed under anesthesia (mixture of ketamine and xilazine). Four days later, rats were separated in three experimental groups: sedentary (SD), submitted to physical activity without (SPA 0%) and with load (SPA 3%). Physical activity was performed during five weeks (one hour per day, five days per week) and the mean arterial pressure (MAP) was measured weekly by tail cuff method. 48 h after the last session of physical activity, the animals were anesthetized (uretana) and MAP and heart hate (HR) were continuously measured (Powerlab system) in different group of rats. Basal MAP levels of 2K1C SD rats were higher than SHAM SD and similar to 2K1C SPA (0% and 3%) rats. However, MAP of 2K1C SPA 0% and 2K1C SPA 3% rats were also similar to SHAM SD rats. Reductions in basal HR were observed in 2K1C SPA 0% and 2K1C SPA 3% groups in comparison to 2K1C SD rats. The bradicardia baroreflex sensibility was determined through alterations in blood pressure (BP) assessed trough i.v. bolus injection of phenylephrine. The baroreflex bradicardia in 2K1C SD was reduced compared to SHAM SD rats. However, physical activity restored the baroreflex bradicardia in 2K1C SPA 0%, but not in 2K1C SPA 3% rats. The hypotension effect produced by microinjection of Ang-(1-7) in the CVLM was similar among all groups SHAM and 2K1C (SD, SPA 0% and SPA 3%). However, the microinjection of a receptor antagonist of Ang-(1-7), A-779, in the CVLM produced a significant hypotensive effect in 2K1C group. A-779 injected in the CVLM produced similar effect on MAP compared to saline in 2K1C SPA 0% and 2K1C SPA 3% and in SHAM (SD, SPA 0% and SPA 3%) rats. Otherwise, the microinjection of A-779 in the CVLM increased the bradicardia baroreflex sensibility in 2K1C SD and 2K1C SPA 3% rats. The microinjection of A-779 blunted the Ang-(1-7) effect in all experimental groups (SD, SPA 0% and SPA 3%) SHAM and 2K1C, for up15 minutes. The percentage of reduction of the dry weight of the kidneys of the animals 2K1C (SD, SPA 0 % and SPA 3 %) was higher than the presented on SHAM SD rats. However, the percentage of reduction of the dry weight of the kidneys of the 2K1C (SD, SPA 0% and SPA 3%) was similar between the 2K1C SD and 2K1C SPA 0% and smaller in 2K1C SPA 3% compared to 2K1C SD animals. The morphological cardiac analysis showed that the 2K1C SD animals presented concentric hypertrophy, however, in the 2K1C SPA 3% animals, the cardiac hypertrophy was eccentric. However, physical activity abolished the hypertrophy in 2K1C SPA 0% rats. Plasma levels of urea in SD, SHAM and 2K1C rats were similar; however, physical activity (0% and 3%) reduced these levels in SHAM and 2K1C rats. There was no differences in plasma levels of creatinina. The 2K1C animals presented an impaired and different kinetic of the lactate in comparison to SHAM groups. The animals 2K1C SD presented a lower production/ removal ratio of blood lactate than SHAM (SD, SPA 0% and SPA 3%) and 2K1C (SPA 0% and SPA 3%) animals. These data suggest that physical activity with and without load reduce basal MAP and HR and restores the neuronal reactivity of the A-779 in the CVLM. However physical activity without load restores the sensibility of bradicardia baroreflex and prevents the cardiac pathological hypertrophy in 2K1C hypertensive rats.

ASSUNTO(S)

1. exercícios físicos - teses. 2. hipertensão renovascular - teses. 3. sistema renina angiotensina - teses. i. universidade federal de ouro preto. ii. título. bioquimica

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