Assessment of exercise-induced alterations in neutrophil function in horses.

OBJECTIVE: To evaluate the effects of a standardized exercise test to exhaustion in horses on leukocyte function ex vivo. ANIMALS: 6 Thoroughbred geldings. PROCEDURES: Blood samples were obtained from each horse before exercise; at exhaustion (termed failure); and at 2, 6, 24, 48, and 72 hours after exercise to evaluate hematologic changes, rate of leukocyte apoptosis, and leukocyte production of reactive oxygen species (ROS) ex vivo. To assess leukocyte function, leukocyte ROS production in response to stimulation with lipopolysaccharide, peptidoglycan, zymosan, and phorbol myristate acetate was evaluated. Apoptosis was evaluated via assessment of caspase activity in leukocyte lysates. RESULTS: In response to lipopolysaccharide, production of ROS by leukocytes was significantly increased at 2 hours and remained increased (albeit not significantly) at 6 hours after exercise, compared with the preexercise value. In the absence of any stimulus, leukocyte ROS production was significantly increased at 6 and 24 hours after exercise. In contrast, ROS production in response to phorbol myristate acetate was significantly decreased at 6, 24, and 72 hours after exercise. Leukocyte ROS production induced by zymosan or peptidoglycan was not altered by exercise. Leukocytosis was evident for 24 hours after exercise, and neutrophilia was detected during the first 6 hours. A significant increase in the rate of leukocyte apoptosis was detected at failure and 72 hours after exercise. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that strenuous exercise undertaken by horses causes alterations in innate immune system functions, some of which persist for as long as 72 hours after exercise.

The impact of varying dietary protein on serum IGF-I, IGFBP-1, and IGFBP-3 during 6 days of physical activity.

This study was designed to investigate the impact of dietary protein intake on serum concentrations of IGF-I and IGFBP-1 and relative amounts of serum IGFBP-3 during 6 d of physical activity. Ten men (23.8 +/- 2.0 y of age) were assigned to 1 of 3 trials in a random crossover design. Each trial was isocaloric but with varying amounts of dietary protein: 50 g, 100 g, or 200 g. Subjects expended 500 kcal through treadmill running or weightlifting on alternate days for 6 d. Fasting blood samples were obtained for measurement of IGF-I, IGFBP-1, and IGFBP-3. Pre-post 24-h urine was measured for urea nitrogen. 50 g/d of protein resulted in a negative nitrogen balance, whereas 100 g/d and 200 g/d resulted in a positive nitrogen balance--200 g greater (P < 0.05) than 50 g and 100 g. Baseline IGF-I, BP-1, and BP-3 were not different among treatments. IGF-I decreased (P = 0.002) during the 6 d. Postintervention IGFBP-I was greater (P = 0.03) than at baseline. Postintervention IGFBP-3 values were not different from baseline or between trials. A 6-d modification of protein intake, while in energy balance, during a strength and conditioning program does not appear to modify serum concentrations of IGF-I or IGFBP-1 or relative amounts of IGFBP-3.