Avaliação de parâmetros fisiológicos e do metabolismo mitocondrial muscular em equinos de concurso completo de equitação submetidos a exercício Intenso

Abstract

The study was carried out to evaluate the changes in physiological parameters muscle’s mitochondrial metabolism related to physical performance before and after maximal exercise treadmill test in eventing horses. The research was conducted at Laboratory of Horse Performance Evaluation, Brazilian Army Cavalry School, RJ, Brazil. Fourteen Brazilian Sport Horses were used, age ranging from 4 to 6 years old, and beginners at any exercise program. The incremental test consisted of three stages: warm up – walk at 1.7m/s for 2 minutes, trot at 4 m/s for 2 minutes and, with the treadmill inclined at 3%, trot at 4 m/s for 2 minutes; gallops – maintaining the inclination, started at a 5m/s speed, increasing the velocity 1m/s every minute until 8m/s, where the horses remained until the exhaustion; and recovery – walk at 1.7m/s for 10 minutes. The samples were collected before and immediately after the end of the test. Blood analyzes were measured in a spectrophotometer using commercial kit. Heart rate was monitored with frequency counter. Muscle samples were obtained from the middle gluteal muscle, it was transferred into ice-cold maintenance solution BIOPS. Mitochondrial respiration was assessed with O2K oxygraph of high resolution (Oroboros). The protocol was: Piruvate/Malate (5/5mM), Adenosine diphosphate (1mM), Succinate (20mM), Adenosine diphosphate (1mM), Cytochrome c (0,01mM), Oligomycin (2μg/ml), Carbonyl-cyane-phenyl-hydrozone (0,001mM), Rotenone (0,5μM), Antimycin A (2,5μM); in MIR05. The results were normalized per segundo per gram of wet weight and expressed as mean and SD. Paired t–test was used and p<0.05 was considered as statistically significant. There was observed the lactate values before and after exercise was 0,4 ± 0,1 mmol/L and 12,09 ± 4,6 mmol/L, respectively. The results of Vl2 and Vl4 were subjected to a regression analysis based on the velocity and estimated in 6.9 ± 2.3m/s and 9.5 ± 3.3 m/s, respectively. The V200 value, 8,9 ± 1,2 m/s, was estimated by linear regression based on the gallops velocities. The values of HT and PPT (p < 0.05) increased after the test. The plasma glucose values decreased during exercise and returned to physiological values during recovery. The CK values increased (p < 0.05) 6 hours after the test ended, but the LHD values weren’t difference after the test. The pH and HCO3- decreased (p < 0.05) after exercise. The K+ and Na+ values after the test increased (p< 0.05) and Ca+ values decreased after the exercise. However, there was an increase in state 3 respiration with Piruvate/Malate substrate, and non-mitochondrial respiration after exercise. The physiological changes showed that the incremental test was intense to horses. There is little change in mitochondrial physiology and increased reactions by enzymes oxidases of gluteus middles muscle after intense exercise