IJCS | Volume 31, Nº6, November / December 2018

611 Moura et al. Diabetic rats and aerobic training Int J Cardiovasc Sci. 2018;31(6)610-618 Original Article other hand, ET on a treadmill resulted in increased capillary density in Wistar rats and an increase in oxidativemuscle fibers. 6 However, a comparison between the effects of ET performed on a treadmill and in a swimming pool is scarce in the literature. We know that the environment where exercise is carried out influences the acquired adaptations. ET in water submersion tests requires different physiological adaptations than training performed on the ground. 7 The main physical properties of water that show clinical relevance are density, buoyancy, hydrostatic pressure, turbulence, viscosity, surface tension, and refractivity. 8 Whereas in the swimming pool the individual is subject to the action of all of these properties to keep the upper airway above the level of water, on the treadmill, the gravitational force and the ground reaction force are the factors that most influence the movement performed out of water. 9 Therefore, the aim of this study was to compare the effects of ET in animals with DM1 and thus perform the characterization of the cardiac and skeletal muscle adaptations following an ET protocol performed in two different ergometers, a treadmill and a swimming pool. Material and methods A cohort of 41 male Wistar rats was studied from 8 to 16 weeks of age. The animals were housed under controlled environmental conditions. The animals were assigned to four experimental groups: sedentary control (CTR) with 10 rats; sedentary diabetes mellitus (DMC) with 11 rats; diabetes mellitus submitted to swimming training (DMS) with 12 rats; diabetes mellitus submitted to treadmill training exercise (DMT) with 9 rats. This study was carried out in accordance with the National Research Council’s Guidelines for the Care and Use of Laboratory Animals, 10 according to the Brazilian legislation on animal testing (Federal Law N˚11,794 of 2008) and was approved by the Ethics and Research Committee (ERC) of UNIFESP (ERC #0384/12). DM1 induction was carried out by administrating streptozotocin (STZ) (Sigma Chemical Company, St. Louis, MO, USA). A single dose of STZ (70 mg/ kg) dissolved in citrate buffer (0.01 M, pH 4.5) was administered through the dorsal vein of the penis. 11,12 Fasting blood glucose was estimated using a reagent strip and glucometer to confirm the diabetic state 7 days after the STZ injection. The animal was considered diabetic when glycemia was ≥ 200 mg/dL. 13,14 Animals with glycemia equal to or higher than 500 mg/dL were excluded from this experiment. The animals in this experiment were trained individually with equal intensity in their respective tracks of aerobic/anaerobic transition (Lan). To identify the metabolic transition zone, a test to measure blood lactate during exercise was carried out to determine the maximum lactate steady state (MLSS). Before performing the test cited earlier, the animals underwent a 5-day adaptation to their respective ergometers for 25 min/day. 15 After 48 h of rest, the end of the adjustment period, the animals of the DMS group performed 20 min of continuous effort in the pool, bearing a load of 3% of their body weight on the first test day, 3.5% on the second day, 4% on the third day, and 4.5% on the fourth test day. Between each test, there was an interval of 48 h to allow for stabilization of serum lactate levels. The incremental load was tied to the back of the animals with an elastic band. During the test, blood samples were collected every 5 min from a cut in the tip of the tail for lactate determination. 15 The animals submitted to treadmill training exercise (DMT) also underwent a lactate test similar to the group submitted to swimming training; however, the test was adapted to the treadmill. After 48 hours of rest at the end of the adaptation period, the animals performed 20 minutes of exercise on each test day. The protocol consists of 4 days of testing, starting on the first day with a velocity of 10m /min, and 5m / min added on each day of the test. Between each test day there was a 48-hour interval for the stabilization of lactate levels. Blood samples were taken every five minutes during the test at the distal end of the animals’ tail to measure the lactate level of each animal. 15 The exercise capacity of all groups was measured on the treadmill and estimated by the total distance. It was evaluated before the beginning of the exercise training protocols and after the end of the exercise training protocols on the eighth week, after 24 hours of rest. The test consisted of an initial walk with an initial speed of 3 m/min for 5 minutes for warming-up, with 3 m/min being added every 3 minutes until the animal showed signs of exhaustion. 16 The exercise training protocol was initiated 20 days after DM induction.