ABC | Volume 110, Nº3, March 2018

Original Article Exercise Training Attenuates Sympathetic Activity and Improves Morphometry of Splenic Arterioles in Spontaneously Hipertensive Rats Marina de Paiva Lemos, 1 Gustavo Ribeiro da Mota, 1 Moacir Marocolo, 2 Carla Cristina de Sordi, 1 Rosângela Soares Chriguer, 3 Octávio Barbosa Neto 1 Universidade Federal do Triângulo Mineiro (UFTM), Uberaba, MG - Brazil 1 Universidade Federal de Juiz de Fora (UFJF), Juiz de Fora, MG - Brazil 2 Universidade Federal de São Paulo, São Paulo, SP - Brazil 3 Mailing Address: Marina de Paiva Lemos • Rua dos Inconfidentes, 242 apt. 102. Postal Code 38025-410, Nossa Senhora da Abadia, Uberaba, MG – Brazil E-mail: marina_plemos@hotmail.com Manuscript received June 23, 2017, revised manuscript October 06, 2017, accepted October 06, 2017 DOI: 10.5935/abc.20180053 Abstract Background: Alterations in the structure of resistance vessels contribute to elevated systemic vascular resistance in hypertension and are linked to sympathetic hyperactivity and related lesions in target organs. Objective: To assess the effects of exercise training on hemodynamic and autonomic parameters, as well as splenic arteriolar damages in male Wistar Kyoto (WKY) and Spontaneously Hypertensive Rats (SHR). Methods: Normotensive sedentary (WKY S ) and trained (WKY T ) rats, and hypertensive sedentary (SHR S ) and trained (SHR T ) rats were included in this study. After 9 weeks of experimental protocol (swimming training or sedentary control), arterial pressure (AP) and heart rate (HR) were recorded in freely moving rats. We assessed the autonomic control of the heart by sympathetic and vagal autonomic blockade. Morphometric analyses of arterioles were performed in spleen tissues. The statistical significance level was set at p < 0.05. Results: Resting bradycardia was observed in both trained groups (WKY T : 328.0 ± 7.3 bpm; SHR T : 337.0 ± 5.2 bpm) compared with their respective sedentary groups (WKY S : 353.2±8.5bpm; SHR S : 412.1±10.4bpm; p<0.001). Exercise training attenuated mean AP only in SHR T (125.9 ± 6.2 mmHg) vs. SHR S (182.5 ± 4.2 mmHg, p < 0.001). The WKY T showed a higher vagal effect (∆HR: 79.0 ± 2.3 bpm) compared with WKY S (∆HR: 67.4 ± 1.7 bpm; p < 0.05). Chronic exercise decreased sympathetic effects on SHR T (∆HR: -62.8 ± 2.8 bpm) in comparison with SHR S (∆HR: -99.8 ± 9.2 bpm; p = 0.005). The wall thickness of splenic arterioles in SHR was reduced by training (332.1 ± 16.0 µm 2 in SHR T vs. 502.7 ± 36.3 µm 2 in SHR S ; p < 0.05). Conclusions: Exercise training attenuates sympathetic activity and AP in SHR, which may be contributing to the morphological improvement of the splenic arterioles. (Arq Bras Cardiol. 2018; 110(3):263-269) Keywords: Exercise; Physical Exertion; Hypertension; Vascular Resistance; Arterioles; Rats. Introduction Essential hypertension is inwardly connected to the blood vessels and is characterized by chronic increases in peripheral vascular resistance, mainly resulting from functional and structural alterations of the microcirculation. These lesions can be both the cause and the consequence of the elevation of arterial pressure (AP). 1 The major pathways that interact to develop morphological changes in arteriolar vessels in hypertension may compromise the splenic vessels (arteriolar hyalinosis, fibrinoid necrosis) and the interstitial space, causing fibrosis. 2-5 The arteriolar hyalinosis occurs by filtration of plasma proteins through the endothelium. It is not exclusive of any disease, being observed in arterioles of normal aging, especially in arterioles of the spleen. However, it occurs earlier and more intense in arterial hypertension. 6 The autonomic nervous system plays a key role in the stabilization of AP control for maintaining homeostasis. In this respect, the literature data show that the sympathetic nervous system (SNS) can reciprocate incisively in the development of some forms of hypertension. Evidence of the participation of this system in the control of normal cardiovascular and metabolic functions and its role in the genesis and maintenance of several diseases is broad. The importance of understanding the workings of the SNS and systems related to it is essential not only to elucidate the path physiology of some diseases, but to understand how drugs that act on the adrenergic system interfere with the evolution of pathologies significantly altering the prognosis of patients. 7 Experimental evidence has shown that chronic exercise produces beneficial effects on the cardiovascular system via alterations in neural control of the circulation. These effects include reductions in AP, sympathetic activity 8 and vascular resistance 9 concomitantly with attenuation in the target-organ damage. 10 If there is relation between exercise training and decrease of vascular resistance, themechanisms bywhich chronic exercise training improves splenic arteriolar morphometry are 263