Participação dos Quimiorreceptores Carotídeos sobre a Regulação Cardiovascular em Ratos Desnutridos
A large number of people die each year due to the intricate aftermath caused by cardiovascular diseases, such as arterial hypertension. Several experimental models have been developed in order to disclose the mechanisms that result in chronic increase of arterial pressure and malnutrition seams to be one of the factors contributing to this pathology. Our laboratory has been studying the control mechanisms of cardiovascular regulatory functions in models of malnourishment. Previous results have shown in some cardiovascular reflexes; baroreflex and Bezold-Jarish reflex, besides an increased vasomotor sympathetic activity. Thus, the main objective of this study was to evaluate the role of carotid chemoreceptors in the cardiovascular regulation among animals submitted to a low protein diet. Male Fisher rats were divided into 4 groups: controls, 15% protein in diet during 35 days (n=18); denervated control (n=08); low-protein, 6% protein in diet (n=18) and low-protein denervated (n=08). Twenty-four hours before the experiment animals were implemented with canulae through the femoral artery and vein for the recording of MAP / HR and drug administration respectively. The chemoreflex evaluation protocol used endovenous potassium cianurete (KCN) injections at different dosages: 5, 10, 15, 20 and 40 ?g/0.1 ml/rat. The rats were submitted to selective chemoreceptor denervation and 24 hours later new recordings of MAP and HR were taken according to the chemoreflex evaluation protocol. Results indicate that low-protein rats have increased MAP and HR when compared to controls (139±3 mmHg and 442±13 bpm) and (115±2 mmHg and 401±8 bpm). In the malnourished animals, the pressoric responses induced by KCN were higher than controls. The bradycardic responses to KCN were also increase, 66% in average, when compared to controls. After chemoreflex denervation, basal levels of MAP and HR, in the low-protein group, significantly increased when compared to values before denervation (135±2 e 156±4 mmHg; 448±16 e 531±19 bpm). In accordance with data from literature, rats from the control group did not change significantly either MAP or HR after chemoreceptor denervation.Our results show an increase in the responsiveness of chemoreflex in the low protein group. In addition, the effect of chemoreceptor denervation on the basal levels of MAP and HR suggest that low protein rats present a tonic inhibitory role of chemoreceptors on the regulation of cardiovascular homeostasis.
Advisor:Maria Lucia Pedrosa; Deoclecio Alvez Chianca; Debora Simões de Almeida Colombari
School:Universidade Federal de Ouro Prêto
Source Type:Master's Thesis
Keywords:1 hipertensão teses 2 quimiorreceptores 3 desnutrição 4 sistema cardiovascular bioquimica
Date of Publication:07/14/2006