AVALIAÇÃO DOS EFEITOS DO ESTRESSE NUTRICIONAL PROMOVIDO PELO DÉFICIT PROTÉICO PÓS-DESMAME SOBRE O SISTEMA CARDIOVASCULAR DE RATOS

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

This work focuses on the nutritional stress caused by post-breast-feeding protein deficiency in rats. Stress-related hormones may alter homeostasis in several body systems; among them, the cardiovascular system was chosen for our present studies. Early works in our laboratory have shown that, in rats, the post-breast-feeding protein malnutrition leads to an increase in cardiac rate (CR) and mean arterial pressure (MAP), besides increasing the variation range of these parameters. Higher baroreflex sensibility and higher renin-angiotensin system activity have also been demonstrated in this type of protein-deficient animals. In view of these findings, we decided to investigate the production of cortisol as a stress indicator in protein-malnourished animals and the possible effect of the excess of this hormone on some cardiovascular parameters. Twelve groups of Fisher rats were employed in the investigation: (i) control groups 1-3, treated with saline solution for 1, 15 and 30 days respectively; (ii) control groups 4-6, treated with ketoconazole for the same time periods; (iii) groups 7-9, protein-underfed animals treated with saline for 1, 15 and 30 days respectively; and (iv) groups 10-12, protein-underfed animals treated with ketoconazole, same time intervals. All control groups were fed on a 15% protein diet during 35 days, while the malnourished animals were on 6% protein. One day before the experiments, an electrocardiographic signal electrode was surgically implanted and a catheter was inserted into the femoral artery for measurement of cardiovascular parameters. Results demonstrated an increased production of cortisol by the underfed animals as compared with the control groups treated with saline for 1 (4.90.5 μg/dL versus 2.10.2 μg/dL respectively), 15 (5.70.5 μg/dL versus 2.50.4 μg/dL) and 30 days (5.60.5 μg/dL versus 2.30.1 μg/dL). The saline-treated underfed animals have shown significantly higher average CR values than the control rats treated with saline for 1 (4182.0 bpm versus 3383.9 bpm), 15 (4272.0 bpm versus 3334.1 bpm) and 30 days (43513 bpm versus 3372.3 bpm). The administration of ketoconazole led to a significant decrease in the production of cortisol by the protein-malnourished animals treated for 15 (1.90.3 μg/dL) and 30 days (0.70.1 μg/dL), when compared with the respective saline-treated underfed animals. There has also been a concomitant reduction in the average CR for the former group when compared with the underfed rats which were saline-treated for 15 days (4272.0 bpm versus 37612 bpm) and 30 days (43513 bpm versus (37912 bpm). Although this is a noticeable decrease, the underfed animals treated with ketoconazole for 1, 15 and 30 days still presented average FC values significantly higher than those from the control rats treated with saline for 1, 15 or 30 days. This result may be related to the increase in the LF/HF ratio observed for the protein-malnourished animals in the cardiac rate variability tests (1 day: 0.890.02 n.u., 15 days: 0.890.04 n.u. and 30 days: 0.850.02 n.u.) compared with the saline-treated control (1 day: 0.550.01 n.u., 15 days 0.590.01 n.u. and 30 days: 0.550.03 n.u.). Taken together, our results demonstrate the stress promoted by post-breast-feeding protein deficiency, as indicated by the higher cortisol levels in the protein-underfed animals, and suggest a joint influence of the excess of cortisol and the increased sympathetic activity on the alteration of the CR values.

ASSUNTO(S)

estresse nutricional sistema cardiovascular de ratos dÉficit protÉico pÓs-desmam fisiologia

ACESSO AO ARTIGO

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