Estudo morfoquantitativo da parede da parte ascendente da aorta de ratos wistar idosos treinados em natação na intensidade do limiar de lactato

Abstract

Aging is associated with the rise in systolic arterial blood pressure, the left ventricular wall thickness and also to a major rigidity of the tunica intima (or inner coat) and tunica media (or middle coat) of arteries due to different factors, such elastic fiber destruction. Exercises have been used as a non-farmacological treatment, a way to prevent cardiovascular diseases, to promote changes in arterial structure and, consequently, to moderate blood pressure. Purpose: to evaluate, in the light of morphological and quantitative aspects, possible alterations in the endothelium of the ascending aorta of 16-month-old Wistar rats submitted to swimming training at anaerobic threshold. Ten male animals were divided into two experimental groups, one control group (n=5) and another group submitted to swimming training (n=5), kept in colective cages, with no restrictions of water or food and trained five times a week, 30 minutes per day, along of eight weeks. The lactate threshold of the first, fourth and eighth weeks of training were determined to the aerobic evaluation. After the experimental period, euthanasia was carried out and there was the removal of the heart and the aorta, which was duly established and prepared in accordance with the histology staining procedures with hematoxylin-eosin, Weigert and Verhoeff. Qualitative and quantitative evaluations were carried out through the use of morphometric and stereologic analysis methods. Results: there was an increase (p<0,05) in thickness, in the cross-sectional area, in elastic fibers and in the distance between the bundles of the nucleus of smooth muscle without altering the diameter of these arteries of trained rats. Conclusion: the aorta of trained rats showed morphological changes consistent with increased elasticity, showing that exercise was an important factor in structural change of the ascending aorta artery of these animals resulting in a stronger and therefore reducing the tangential stress in the arterial wall during exercise and at the rest.