Assessment of serum myokines and markers of inflammation associated with exercise in endurance racing sled dogs.

BACKGROUND: The endurance sled dog is the ultimate endurance athlete in which to examine the exercise-associated acute phase and myokine responses that might be related to changes in muscle metabolism and damage. An inciting cause for increased C-reactive protein has yet to be elucidated, which might involve interleukin-6 and other myokines. OBJECTIVES: To examine concentrations of interleukin-6 (IL-6), interleukin-15 (IL-15), interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α), and markers of the inflammatory response of exercise; monocyte chemoattractant protein-1(MCP-1) and C-reactive protein (CRP) before, during, and after an endurance racing event. ANIMALS: 26 sled dogs completing a 1650-km race. METHODS: In a prospective study, cephalic venipuncture was performed before racing, at the midpoint, and after racing. Body weight and serum CRP, MCP-1, IL-15, IL-8, IL-6, and TNF-α concentrations were evaluated using enzyme-linked immunoabsorbance-based assays or a luminex multiplex assay. RESULTS: There were no significant differences in concentrations of IL-6, IL-15, IL-8, or TNF-α at the 3 time points, whereas there were significant increases in MCP-1 (median and range-start: 86 pg/mL [30-1845]; midpoint: 179 pg/mL [53-730]; finish: 180 pg/mL [21-1294]; P < .01) and CRP (median and range-start: 18 µg/mL [11-58]; midpoint: 76 µg/mL [12-198]; finish: 60 µg/mL [12-170]; P < .01) at the midpoint and race finish. There was a significant linear relationship between MCP-1 and IL-6 (R = 0.68; P < .01). CONCLUSIONS AND CLINICAL SIGNIFICANCE: The inflammatory response to exercise increases as measured by MCP-1 during and after endurance exercise in sled dogs. IL-6 appears to be associated with MCP-1; however, the reasons for increases in the acute phase response (CRP) cannot be attributed to IL-6 or other myokines. IL-6 and MCP-1 concentrations might be useful in future investigations of exertional rhabdomyolysis.

Effect of sucralfate on total carbon dioxide concentration in horses subjected to a simulated race test.

The purpose of this study was to test the hypothesis that sucralfate, a gastric ulcer medication, would alter plasma concentrations of total carbon dioxide (tCO2), lactate (LA), sodium (Na+), potassium (K+), chloride (Cl-) and total protein (TP), as well as calculated plasma strong ion difference (SID) and packed cell volume (PCV) in horses subjected to a simulated race test (SRT). Six unfit Standardbred mares (approximately 520 kg, 9-18 years) were used in a randomized crossover design with the investigators blinded to the treatment given. The horses were assigned to either a control (40-50 mL apple sauce administered orally (PO)) or a sucralfate (20 mg/kg bodyweight dissolved in 40-50 mL apple sauce administered PO) group. Each horse completed a series of SRTs during which blood samples were taken via jugular venipuncture at five sampling intervals (prior to receiving treatment, prior to SRT, immediately following exercise, and at 60 and 90 min post-SRT). During the SRTs, each horse ran on a treadmill fixed on a 6% grade for 2 min at a warm-up speed (4 m/s) and then for 2 min at a velocity predetermined to produce VO2max. Each horse then walked at 4 m/s for 2 min to complete the SRT. Plasma tCO2, electrolytes, LA, and blood PCV and TP were analysed at all intervals. No differences (P>0.05) were detected between control and sucralfate for any of the measured variables. There were differences (P<0.05) in tCO2, SID, PCV, TP, LA and electrolyte concentrations relative to sampling time. However, these differences were attributable to the physiological pressures associated with acute exercise and were not an effect of the medication. It was concluded that sucralfate did not alter plasma tCO2 concentration in this study.