ABSTRACT
Exercise training (Ex) has been recommended for its beneficial effects in hypertensive states. The present study evaluated the time-course effects of Ex without workload on mean arterial pressure (MAP), reflex bradycardia, cardiac and renal histology, and oxidative stress in two-kidney, one-clip (2K1C) hypertensive rats. Male Fischer rats (10 weeks old; 150–180 g) underwent surgery (2K1C or SHAM) and were subsequently divided into a sedentary (SED) group and Ex group (swimming 1 h/day, 5 days/week for 2, 4, 6, 8, or 10 weeks). Until week 4, Ex decreased MAP, increased reflex bradycardia, prevented concentric hypertrophy, reduced collagen deposition in the myocardium and kidneys, decreased the level of thiobarbituric acid-reactive substances (TBARS) in the left ventricle, and increased the catalase (CAT) activity in the left ventricle and both kidneys. From week 6 to week 10, however, MAP and reflex bradycardia in 2K1C Ex rats became similar to those in 2K1C SED rats. Ex effectively reduced heart rate and prevented collagen deposition in the heart and both kidneys up to week 10, and restored the level of TBARS in the left ventricle and clipped kidney and the CAT activity in both kidneys until week 8. Ex without workload for 10 weeks in 2K1C rats provided distinct beneficial effects. The early effects of Ex on cardiovascular function included reversing MAP and reflex bradycardia. The later effects of Ex included preventing structural alterations in the heart and kidney by decreasing oxidative stress and reducing injuries in these organs during hypertension.
Subject(s)
Animals , Male , Hypertension, Renovascular/physiopathology , Kidney/pathology , Myocardium/pathology , Oxidative Stress/physiology , Physical Conditioning, Animal/physiology , Arterial Pressure/physiology , Baroreflex/physiology , Bradycardia/metabolism , Bradycardia/pathology , Catalase/metabolism , Heart Rate/physiology , Kidney/metabolism , Myocardium/enzymology , Myocardium/metabolism , Renal Artery/surgery , Sedentary Behavior , Surgically-Created Structures , Time Factors , Thiobarbituric Acid Reactive Substances/analysisABSTRACT
Considera-se bradirritmia uma fequência cardíaca menor que 50 bpm. Evidentemente, esse conceito é relativo à situação metabólica e à idade do paciente, mesmo porque uma frequência cardíaca de 45bpm ou menos pode ser normal durante o sono em pacientes idosos, assim como uma frequência de 70 bpm constituti bradicardia em recém-nascidos ou em pacientes com febre. Isso demonstra que o diagnóstico depende do quadro clínico do paciente.