Serum chemistry alterations in Alaskan sled dogs during five successive days of prolonged endurance exercise

OBJECTIVE: To determine the impact of successive days of endurance exercise on select serum chemistry values in conditioned Alaskan sled dogs. DESIGN: Prospective cohort study. ANIMALS: 10 conditioned Alaskan sled dogs. PROCEDURES: All dogs ran 160 km/d for 5 consecutive days. Serum was obtained prior to exercise and immediately after each exercise run; all samples were obtained before dogs were fed. Serum electrolyte, mineral, protein, total bilirubin, urea nitrogen, creatinine, and cardiac troponin-I concentrations and serum alkaline phosphatase, alanine aminotransferase, creatine kinase, and aspartate aminotransferase activities were measured. Data were analyzed by means of analysis of covariance for a randomized complete block design with dog as a blocking variable, time as a covariate, and distance run as the treatment of interest. Least square mean values were compared with values obtained prior to exercise, and linear and quadratic contrasts were examined. RESULTS: Serum globulin concentration was low prior to exercise (mean +/- SD, 2.2 +/- 0.3g/dL) and progressively decreased as exercise continued. Exercise was associated with increases in serum chloride, urea nitrogen, and cardiac troponin-I concentrations and serum alanine aminotransferase, creatine kinase, and aspartate aminotransferase activities and with progressive decreases in serum potassium, total protein, and albumin concentrations. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that multiple successive days of endurance exercise resulted in mild aberrations in serum chemistry variables in conditioned sled dogs. Changes likely reflected the metabolic stresses of prolonged endurance exercise as well as dietary composition. Hypoglobulinemia in resting, conditioned sled dogs may reflect the immunosuppressive or catabolic effects of intense endurance training.     

Effect of dietary supplements containing antioxidants on attenuation of muscle damage in exercising sled dogs

OBJECTIVE: To determine whether dietary antioxidants would attenuate exercise-induced increases in plasma creatine kinase (CK) activity in sled dogs. ANIMALS: 41 trained adult sled dogs. PROCEDURE: Dogs, randomly assigned to 2 groups, received the same base diet throughout the study. After 8 weeks on that diet, 1 group (21 dogs) received a daily supplement containing vitamins E (457 U) and C (706 mg) and beta-carotene (5.1 mg), and a control group (20 dogs) received a supplement containing minimal amounts of antioxidants. After 3 weeks, both groups performed identical endurance exercise on each of 3 days. Blood samples were collected before and 3 weeks after addition of supplements and after each day of exercise. Plasma was analyzed for vitamins E and C, retinol, uric acid, triglyceride, and cholesterol concentrations, total antioxidant status (TAS), and CK activity. RESULTS: Feeding supplements containing antioxidants caused a significant increase in vitamin E concentration but did not change retinol or vitamin C concentrations orTAS. Exercise caused significantly higher CK activity, but did not cause a significant difference in CK activity between groups. Exercise was associated with significantly lower vitamin E, retinol, and cholesterol concentrations and TAS but significantly higher vitamin C, triglyceride, and uric acid concentrations in both groups. CONCLUSIONS AND CLINICAL RELEVANCE: Use of supplements containing the doses of antioxidants used here failed to attenuate exercise-induced increases in CK activity. Muscle damage in sled dogs, as measured by plasma CK activity, may be caused by a mechanism other than oxidant stress.     

Effects of administration of IH901, a ginsenoside intestinal metabolite,on muscular and pulmonary antioxidant functions after eccentric exercise

This study was conducted to investigate whether administration of IH901, a ginseng intestinal metabolite, ameliorates exercise-induced oxidative stress while preserving antioxidant defense capability in rat skeletal muscles and lung. Eight adult male Sprague-Dawley rats per group were randomly assigned to the resting control, exercise control, resting with IH901 (25, 50, and 100 mg/kg) consumption (R/IH901), or exercise with IH901 (25, 50, and 100 mg/kg) consumption (E/IH901) group. The trained groups ran 35 min 2 days/week for 8 weeks. To analyze the IH901-training interaction, serum biochemical analysis, lipid peroxidation, citrate synthase, protein oxidation, antioxidant and superoxide dismutase in skeletal muscles and lung tissue were measured. Compared to the exercise control group, animals that consumed IH901 had significantly increased exercise endurance times (p < 0.05) and decreased plasma creatine kinase and lactate dehydrogenase levels (p < 0.05), while those in the E/IH901 groups had increased citrate synthase and anti-oxidant enzymes and decreased lipid peroxidation and protein oxidation (p < 0.05). In conclusion, IH901 consumption in aging rats after eccentric exercise has beneficial effects on anti-inflammatory and anti-oxidant activities through down-regulation of pro-inflammatory mediators, lipid peroxidation, and protein oxidation and up-regulation of anti-oxidant enzymes.     

Effects of dietary antioxidant supplementation on oxidative damage and resistance to oxidative damage during prolonged exercise in sled dogs

OBJECTIVES: To determine effects of dietary antioxidant supplementation on plasma concentrations of antioxidants, exercise-induced oxidative damage, and resistance to oxidative damage during exercise in Alaskan sled dogs. ANIMALS: 62 Alaskan sled dogs. PROCEDURE: Dogs were matched for age, sex, and ability and assigned to 1 of 3 groups: sedentary and nonsupplemented (control [C]; n = 21), exercised and supplemented (S; 22), and exercised and nonsupplemented (N; 19). Dogs in group S were given 400 units of alpha-tocopherol acetate, 3 mg of beta-carotene, and 20 mg of lutein orally per day for 1 month, then dogs in groups S and N completed 3 days of exercise. Blood samples were collected before and after 1 and 3 days of exercise and after 3 days of rest. Plasma antioxidant concentrations were determined, and oxidative damage to DNA (plasma 7,8 dihydro-8-oxo-2'deoxyguanosine [8-oxodG] concentration) and membrane lipids (plasma hydroperoxide concentration) and resistance of plasma lipoproteins to oxidation were assessed. RESULTS: Supplementation increased plasma concentrations of alpha-tocopherol, beta-carotene, and lutein. Plasma concentration of alpha-tocopherol increased and concentration of lutein decreased in group S with exercise. Concentration of 8-oxodG decreased in group S but increased in group N during and after exercise. Lag time of in vitro oxidation of lipoprotein particles increased with exercise in group S only. CONCLUSIONS AND CLINICAL RELEVANCE: Dietary supplementation with antioxidants resulted in increased plasma concentrations of antioxidants. Moreover, supplementation decreased DNA oxidation and increased resistance of lipoprotein particles to in vitro oxidation. Antioxidant supplementation of sled dogs may attenuate exercise-induced oxidative damage.     

Effects of endurance training on standard and signal-averaged electrocardiograms of sled dogs

OBJECTIVE: To determine the effect of endurance training on QRS duration, QRS-wave amplitude, and QT interval. ANIMALS: 100 sled dogs in Alaska. PROCEDURE: Dogs were examined in early September (before training) and late March (after training). During the interim, dogs trained by pulling a sled with a musher (mean, 20 km/d). Standard and signal-averaged ECG were obtained before and after training. RESULTS: Endurance training significantly increased mean QRS duration by 4.4 milliseconds for standard ECG (mean +/- SEM; 62.3 +/- 0.7 to 66.7 +/- 0.6 milliseconds) and 4.3 milliseconds for signal-averaged ECG (51.5 +/- 0.7 to 55.8 +/- 0.6 milliseconds) without changing body weight. Increase in QRS duration corresponded to a calculated increase in heart weight (standard ECG, 23%; signal-averaged ECG, 27%). Signal-averaged QRS duration was correlated with echocardiographically determined left ventricular diastolic diameter for the X orthogonal lead (r = +0.41), Y orthogonal lead (r = +0.33), and vector (r = +0.35). Training also increased QT interval (234 +/- 2 to 249 +/- 2 milliseconds) and R-wave amplitude in leads II and rV2, increased peak-to-peak voltage and S-wave amplitude in the Y orthogonal lead, and decreased Q-wave amplitude in the Y orthogonal lead. CONCLUSIONS AND CLINICAL RELEVANCE: Electrocardiographic changes reflected physiologic cardiac hypertrophy in these canine athletes in response to repetitive endurance exercise. The QRS duration increases in response to endurance exercise training and, therefore, may be of use in predicting performance in endurance activities.     

Exercise induced hypercoagulability,increased von Willebrand factor and decreased thyroid hormone concentrations in sled dogs

Background

Sled dogs performing endurance races have been reported to have a high incidence of gastric erosions or ulcerations and an increased risk of gastro intestinal bleeding leading to death in some cases. In addition, these dogs also become hypothyroid during training and exercise. Canine hypothyroidism has been shown to correlate with decreased von Willebrand factor antigen and potentially increased bleeding tendency. Whether increased gastro intestinal bleeding risk is exacerbated due to changes in the hemostatic balance is unknown. The aim of this study was to investigate the hemostatic balance in sled dogs before and after exercise and in addition evaluate any correlation to thyroid status. Twenty sled dogs have been assessed in untrained and trained condition and immediately after exercise. The first sample was collected in the autumn following a resting period, and subsequently the dogs were exposed to increased intensity of training. After four months the peak of physical condition was reached and a 68 km long sled pulling exercise was performed. Samples were collected before and immediately after the exercise. Evaluated parameters were: plasma thromboelastographic (TEG) R, SP, α and MA, activated partial thromboplastin time (aPTT), prothrombin time (PT), fibrinogen, von Willebrand factor (vWf), D-dimer, platelet number, thyroid hormones, hematocrit and C-reactive protein (CRP).

Results

Exercise induced an overall hypercoagulable state characterized by significant decreases of TEG R and SP and an increase of α, increased concentrations of plasma vWf and decreased aPTT. In addition, a proinflammatory status was seen by a significant increase of serum CRP concentrations. Thyroid status was confirmed to be hypothyroid as training and exercise induced significant decrease of thyroxin (T4), free thyroxin (fT4) and thyroxin stimulating hormone (TSH) concentrations. Fibrinogen decreased significantly and PT increased. The training-induced changes showed correlation between T4, fT4 and aPTT and correlation between TSH and fibrinogen. Exercise-induced changes showed correlation between T4 and PT.

Conclusions

Exercise was associated with a hypercoagulable state and an increase of vWf concentration in this group of sled dogs. Decreased thyroid hormone concentrations after training and exercise were confirmed, but were associated with increased and not decreased vWf in this group of sled dogs.     

The Influence of High‐Intensity Moderate Duration Exercise on Cardiac Troponin I and C‐Reactive Protein in Sled Dogs

Background: C‐reactive protein (CRP) and cardiac troponin I (cTnI) are biomarkers of systemic inflammation and cardiac damage, respectively. Objective: To investigate the effects of short‐duration high‐intensity exercise on plasma cTnI and serum CRP concentrations in sprint racing sled dogs. Animals: Twenty‐two Alaskan sled dogs of 2 different teams participating in a 2‐day racing event. Methods: In this prospective field study, cephalic venipuncture was performed on all dogs before racing and immediately after racing on 2 consecutive days. Plasma cTnI and serum CRP concentrations were evaluated at each time point. Results: There was a mild, significant rise (P < .01) in median cTnI concentrations from resting (0.02 ng/mL; 0.0–0.12 ng/mL) on both days after racing (day 1 = 0.06, 0.02–0.2 ng/mL; day 2 = 0.07, 0.02–0.21 ng/mL). Serum CRP concentrations showed a mild significant increase (P < .01) on day 2 after racing mean (9.2 ± 4.6 μg/mL) as compared with resting (6.5 + 4.3 μg/mL) and day 1 after racing (5.0 + 2.9 μg/mL). Neither cTnI or CRP concentrations exceeded the upper reference range for healthy dogs. Conclusions and Clinical Relevance: Strenuous exercise of short duration did not result in cTnI concentrations above the reference range for healthy dogs. Although increased after 2 days of short‐duration strenuous exercise, CRP did not reach concentrations suggestive of inflammation, as reported previously in the endurance sled dogs. Therefore, we surmise that moderate exercise does not present a confounding variable in the interpretation of cTnI and CRP concentrations in normal dogs.     

Effects on plasma endotoxin and eicosanoid concentrations and serum cytokine activities in horses competing in a 48-, 83-, or 159-km endurance ride under similar terrain and weather conditions

OBJECTIVE: To determine plasma endotoxin concentration in horses competing in a 48-, 83-, or 159-km endurance race and its importance with regard to physical, hematologic, or serum and plasma biochemical variables. ANIMAL: 3 horses. PROCEDURE: Weight and rectal temperature measurements and blood samples were obtained before, during, and after exercise. Blood samples were analyzed for plasma endotoxin concentration; serum antiendotoxin antibody titers; thromboxane B2 (TxB2) and 6-keto-prostaglandin F1alpha (PGF1alpha) concentrations; tumor necrosis factor alpha (TNFalpha) and interleukin-6 (IL-6) activities; WBC, plasma protein, lactate, serum electrolyte, and calcium concentrations; PCV; and creatine kinase activity. RESULTS: Detection of plasma endotoxin increased during exercise for horses competing at all distances but occurred more frequently in the 48- and 83-km groups. Plasma lactate concentration was significantly greater when endotoxin was concurrently detected. Endotoxin in plasma was not significantly associated with success of race completion. Plasma TxB2 and PGF1alpha concentrations and serum IL-6 activity significantly increased with exercise. Horses that had an excellent fitness level (as perceived by their owners) had greater decreases in serum antiendotoxin antibody titers during exercise than did horses perceived as less fit. In horses with better finish times, TxB2 and PGF1alpha concentrations were significantly greater and TNFalpha activity was significantly less than that of slower horses. CONCLUSIONS AND CLINICAL RELEVANCE: Endotoxemia developed during endurance racing, but was significantly correlated with increased plasma lactate concentration and not with other variables indicative of endotoxemia. Plasma TxB2 and PGF1alpha concentrations and serum TNFalpha activity may be associated with performance success.     

Effects of racing and nontraining on plasma thyroid hormone concentrations in sled dogs

OBJECTIVE: To determine the effects of racing and nontraining on plasma thyroxine (T4), free thyroxine (fT4), thyroid-stimulating hormone (TSH), and thyroglobulin autoantibody (TgAA) concentrations in sled dogs and compare results with reference ranges established for dogs of other breeds. DESIGN: Cross-sectional study. ANIMALS: 122 sled dogs. PROCEDURE: Plasma thyroid hormone concentrations were measured before dogs began and after they finished or were removed from the Iditarod Trail Sled Dog Race in Alaska and approximately 3 months after the race. RESULTS: Concentrations of T4 and fT4 before the race were less than the reference range for nonsled dogs in 26% and 18% of sled dogs, respectively. Immediately after racing, 92% of sled dogs had plasma T4 concentrations less than the reference range. Three months after the race, 25% of sled dogs had plasma T4 concentrations less than the reference range. For T4, fT4, TSH, and TgAA, significant differences were not detected in samples collected before the race versus 3 months later. CONCLUSIONS AND CLINICAL RELEVANCE: Plasma T4, fT4, and TSH concentrations decreased in dogs that complete a long distance sled dog race. Many clinically normal sled dogs have plasma T4 and fT4 values that are lower than the reference range for nonsled dogs. We suggest that the reference ranges for sled dogs are 5.3 to 40.3 nmol/L and 3.0 to 24.0 pmol/L for plasmaT4 and fT4 concentrations, respectively, and 8.0 to 370 mU/L for TSH.     

Effect of strenuous exercise on urine concentrations of homovanillic acid, cortisol, and vanillylmandelic acid in sled dogs

OBJECTIVE: To determine whether prolonged exercise by conditioned sled dogs affects urine concentrations of homovanillic acid (a metabolite of dopamine), vanillylmandelic acid (a metabolite of norepinephrine and epinephrine), and cortisol. ANIMALS: 24 conditioned Alaskan sled dogs (2 to 8.5 years old) that were in training for a multiday endurance race. PROCEDURES: Voided urine samples were collected from 4 groups of dogs (randomly selected from 54 dogs) after no exercise (control group; n = 6 dogs), completion of a 160km run (group A; 3), completion of a 420-km run (group B; 7), and completion of a 560-km run (group C; 6). Urine cortisol concentrations were determined by use of an immunoassay technique; urine vanillylmandelic acid and homovanillic acid concentrations were measured via high-performance liquid chromatography. RESULTS: Compared with the control group, urine cortisol concentration in groups A, B, and C was significantly different (5.33 x 10(4) +/- 2.62 x 10(4) microg/dL vs 1.04 x 10(4) +/- 2.31 x 10(5) microg/dL, 8.88 x 10(4) +/- 5.49 x 10(4) microg/dL, and 6.31 x 10(4) +/- 5.09 x 10(4) microg/dL, respectively). Urine homovanillic acid concentration did not differ among the 4 groups. Vanillylmandelic acid was not detected in any urine samples. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that prolonged exercise by sled dogs did not affect urine homovanillic acid concentration but did increase urinary cortisol secretion, which is indicative of adrenocortical stimulation. The apparent lack of vanillylmandelic acid in voided urine samples requires further investigation.     

Plasma thyroid hormone concentrations in dogs competing in a long-distance sled dog race

Plasma thyroxine (T4), 3,5,3'-triiodothyronine (T3), total protein, and albumin concentrations were measured in 15 dogs both before and after completion, and in an additional 16 dogs before and 24 dogs after completion, of a long-distance sled dog race. The plasma T4 concentration (mean +/- SD) decreased significantly from 18.2 +/- 5.4 nmol/L before to 14.3 +/- 3.5 nmol/L after the race in dogs evaluated at both times and decreased significantly from 21.8 +/- 10.5 nmol/L before to 15.8 +/- 4.9 nmol/L after the race in dogs sampled only before or only after the race. The mean plasma T3 concentrations in dogs measured twice decreased significantly from 1.20 +/- 0.48 nmol/L before to 0.74 +/- 0.42 nmol/L after the race, as well as in dogs measured either before (1.28 +/- 0.36 nmol/L) or after (0.69 +/- 0.28 nmol/L) the race, respectively. Plasma total protein and albumin concentrations decreased significantly after completion of the race. No significant change was noted in 4 control dogs that did not compete in the race and were tested during a similar time period. The plasma concentrations of T4 and T3 were lower than the normal reference range established for this laboratory in 23 and 39%, respectively, of Alaskan sled dogs tested before the race. Plasma thyroid hormone concentrations frequently are below normal in conditioned Alaskan sled dogs and are further reduced after prolonged submaximal exercise.     

The physiological response of siberian husky dogs to exercise: effect of interval training

Five Siberian Husky Dogs participated in an initial study to determine their physiological response to three types of exercise. Blood samples were taken prior to, and three minutes following, a 7.5 km free run and 6 km team sled run for the determination of hemoglobin, hematocrit, red and white blood cell counts, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, lactate dehydrogenase, creatine phosphokinase and serum glutamic pyruvic transaminase. Samples were also taken following a 90s sprint run. Heart rate was taken immediately after each run by palpation of the femoral pulse. Average heart rates following the 90s, 7.5 km and 6 km runs were 190 bpm, 211 bpm and 166 bpm, respectively. Mean lactate concentrations following the 90s, 7.5 km and 6 km runs were 1.74 mMol · 1⁻¹, 0.70 mMol · 1⁻¹, and 3.06 mMol · 1⁻¹, respectively. Elevation of lactate dehydrogenase and creatine phosphokinase was greatest following the 6 km sled run. Three of the above dogs were then studied before and after a 12 week interval training program, while three other dogs served as controls. The animals completed a three stage, submaximal treadmill test prior to and following the program. Pre and post blood samples were taken, and rectal temperature and heart rate were recorded continuously throughout the test. An analysis of variance was used to examine the significance of differences between and within groups. Although the response of heart rate, lactate, temperature and serum enzymes to submaximal exercise did not change with training significant differences between groups suggested that a more prolonged program may have resulted in such adaptations.     

Effect of exercise on the mobilization of retinol and retinyl esters in plasma of sled dogs

Fasting dogs do transport vitamin A (VA) in plasma not only as retinol but predominantly as retinyl esters. Contrary to retinol, nothing is known concerning the effects of athletic performance on plasma retinyl ester concentrations. The aim of this study was therefore to examine whether physical stress because of exercise and modification of the oxidative stress by supplementation of alpha-tocopherol influences the concentrations of retinol and retinyl esters in plasma of sled dogs. The study was carried out on 41 trained adult sled dogs, which were randomly assigned into two groups. One group (19 dogs) was daily substituted with 50 mg dl-alpha-tocopheryl acetate per kilogram body weight and the control group (22 dogs) was maintained on a basal diet during 3 months prior to exercise. The plasma concentrations of retinol, retinyl esters, alpha-tocopherol and triglycerides were measured immediately before, directly after and 24 h after exercise. The supplementation of alpha-tocopheryl acetate had no effect on plasma retinol and retinyl ester concentrations at any measurement time point. However, retinyl ester levels doubled in the non-supplemented group immediately after the race (p < 0.001), whereas in the supplemented group similar high levels were observed not until 24 h post-racing (p < 0.001). The high levels of retinyl esters were paralleled to some extent by an increase in plasma triglyceride concentrations, which were significantly higher 24 h post-racing than immediately before (p < 0.001) and after exercise (p < 0.001) in both groups. The increase in retinyl ester concentrations might be indicative of their mobilization from liver and adipose tissue. Whether plasma retinyl esters can be used as an indicator for the extent of nutrient mobilization during and post-exercise in sled dogs remains to be elucidated.     

Assessment of alterations in triglyceride and glycogen concentrations in muscle tissue of Alaskan sled dogs during repetitive prolonged exercise

OBJECTIVE: To assess changes in muscle glycogen (MG) and triglyceride (MT) concentrations in aerobically conditioned sled dogs during prolonged exercise. ANIMALS: 54 Alaskan sled dogs fed a high-fat diet. PROCEDURES: 48 dogs ran 140-km distances on 4 consecutive days (cumulative distance, up to 560 km); 6 dogs remained as nonexercising control animals. Muscle biopsies were performed immediately after running 140, 420, or 560 km (6 dogs each) and subsequently after feeding and 7 hours of rest. Single muscle biopsies were performed during recovery at 28 hours in 7 dogs that completed 560 km and at 50 and 98 hours in 7 and 6 dogs that completed 510 km, respectively. Tissue samples were analyzed for MG and MT concentrations. RESULTS: In control dogs, mean +/- SD MG and MT concentrations were 375 +/- 37 mmol/kg of dry weight (kgDW) and 25.9 +/- 10.3 mmol/kgDW, respectively. Compared with control values, MG concentration was lower after dogs completed 140 and 420 km (137 +/- 36 mmol/kgDW and 203 +/- 30 mmol/kgDW, respectively); MT concentration was lower after dogs completed 140, 420, and 560 km (7.4 +/- 5.4 mmol/kgDW; 9.6 +/- 6.9 mmol/kgDW, and 6.3 +/- 4.9 mmol/kgDW, respectively). Depletion rates during the first run exceeded rates during the final run. Replenishment rates during recovery periods were not different, regardless of distance; only MG concentration at 50 hours was significantly greater than the control value. CONCLUSIONS AND CLINICAL RELEVANCE: Concentration of MG progressively increased in sled dogs undergoing prolonged exercise as a result of attenuated depletion.     

Effects of training and strenuous exercise on hematologic values and peripheral blood leukocyte subsets in racing sled dogs

OBJECTIVE: To determine the effects of training and sustained submaximal exercise on hematologic values in racing sled dogs. DESIGN: Cohort study. ANIMALS: 39 Alaskan sled dogs bred for endurance racing. Procedures-Blood samples were collected prior to initiation of a 7-month training regimen (n=39), after completion of the training regimen (19), and after completion of an 1,100-mile race (9), and a CBC, differential cell count, and flow cytometry for leukocyte surface antigens were performed. RESULTS: Both training and exercise caused significant decreases in PCV and hemoglobin concentration and significant increases in total WBC count. In contrast, training and exercise were not found to have significant effects on absolute numbers or fractions of CD4+ or CD8+ lymphocytes, other than a significant increase in the fraction of CD8+ lymphocytes associated with training. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that training and exercise induced changes in several hematologic values in racing sled dogs. Extracellular fluid volume expansion was the likely explanation for the training-induced decrease in PCV, and acute blood loss secondary to gastrointestinal tract bleeding was likely responsible for the decrease in PCV associated with acute exercise.     

Biochemical and antioxidant changes in plasma and erythrocytes of pentathlon horses before and after exercise

Abstract: Physical exercise in the horse induces a series of normal physiological and biochemical adaptations. Increasing metabolism and oxygen uptake may induce oxidative stress in various organs. The aim of this study was to examine exercise-induced changes in some plasma and RBC biochemical and antioxidant variables in pentathlon horses. Blood samples were taken from 14 horses before, immediately after, and 24 hours after competing in two 1-minute runs of intense exercise over jumps. The peak intensity periods were preceded by a 20-minute warm-up and separated by a 20-minute break. The following plasma biochemical analytes were determined: total protein, uric acid, and lactate concentrations, and lactate dehydrogenase (LDH) and creatine kinase (CK) activities. Total antioxidant status (TAS) and the ferric reducing ability of plasma (FRAP) also were measured. Thiobarbituric acid-reactive substances (TBARS), reduced glutathione (GSH), and total protein concentrations, and glutathione peroxidase (GSHPx) and superoxide dismutase (SOD) activities were determined in RBC hemolysates. Significantly increased concentrations of total protein, lactate, and FRAP, and increased activities of CK and LDH were observed immediately postexercise compared with pre-exercise samples (P < .05). All results returned to approximately initial values after 24 hours of rest. RBC GSH and TBARS concentrations did not change immediately after exercise, but decreased after 24 hours of rest (P < .05). Plasma uric acid and FRAP values were positively correlated in a linear model ( r = .78). In summary, the type of exercise applied in this study, which can be considered quite usual for pentathlon horses, caused detectable biochemical and lipid peroxidative changes in plasma and RBCs. FRAP and TAS values changed in opposite directions, indicating that when antioxidant capacity is assessed using different methods, highly different results may be obtained.     

Biochemical and Antioxidant Changes in Plasma, Serum, and Erythrocytes of Horses before and after a Jumping Competition

We designed an experiment to determine the concentrations of a marker of lipid peroxidation in erythrocytes of horses submitted to jumping competitions. Erythrocytes of exercised horses showed a significant increase in the concentration of thiobarbituric acid-reactive species content immediately after exercise (P < .001), which returned to normal levels 24 hours after exercise. Nonprotein sulfhydryl groups and superoxide dismutase activity (EC 1.15.1.1) in erythrocytes were significantly higher 24 hours after exercise, as compared with the resting period and control group (P < .001). Immediately after exercise, horses had increased serum concentrations of uric acid (P < .002) and plasma lactate, as well as increased creatine kinase (EC 2.7.3.2) and lactate dehydrogenase (EC 1.1.1.28) activities (P < .001), as compared with resting period and control group. All parameters returned to normal values 24 hours after exercise, except for uric acid serum levels that remained increased (P < .001). We conclude that the oxidative stress in erythrocytes of exercised horses may contribute to tissue damage. In addition, our results showed that horses submitted to a jumping competition showed higher production of free radicals and as a consequence, lipid peroxidation.     

Hypogammaglobulinemia in Racing Alaskan Sled Dogs

Background: Serum immunoglobulin dynamics have not been studied in racing sled dogs, despite hypoglobulinemia having been reported during racing events.
Hypothesis/Objectives: Hypoglobulinemia in racing sled dogs is associated with decreases in serum IgA, IgE, IgG, and IgM concentrations during prolonged exercise.
Animals: One hundred and fifty-seven Alaskan sled dogs that successfully completed a 1,000 mile race.
Methods: Serum was obtained from 118 sled dogs within 1 month before the race and within 12 hours after completing the race. Serum also was obtained after 4 months of rest from 51 dogs that successfully completed the race, including 12 previously sampled dogs. Serum total protein ([TP]), albumin, and globulin ([Gl]) were measured, and serum IgA, IgE, IgG, and IgM were quantified by ELISA.
Results: The proportion of dogs with [Gl] ≤ 2.2 g/dL was significantly greater immediately after racing (38 of 118 dogs, 32.2%) than before racing (21 of 118 dogs, 17.8%, P = .005). Four months after racing, [Gl] was ≤ 2.2 g/dL in 23.5% (12 of 51) of dogs. [IgG] was significantly lower before (8.21 ± 4.95 mg/mL) and immediately after (7.97 ± 5.62) racing compared with 4 months after racing (18.88 ± 5.76). Serum [IgM] and [IgE] were higher and [IgA] was lower before racing compared with immediately after racing.
Conclusions and Clinical Importance: Sled dogs participating in long-distance racing have substantial decreases in [IgG] in addition to decreases in [IgM] and [IgE]. The pronounced hypogammaglobulinemia observed in a large proportion of racing sled dogs might predispose them to infectious disease.     

Biochemical and metabolic changes due to exercise in sprint-racing sled dogs: implications for postexercise carbohydrate supplements and hydration management

Evaluations of biochemical changes associated with spring-style sled dog racing indicate that differences in cortisol, lactate, and serum glucose levels suggest exercise of moderate duration (but high intensity) has metabolic demands that dif-fer from those for typical endurance sled dog racing. Additionally, hematocrit, albumin, sodium, chloride, and blood urea nitrogen levels decreased in one team of dogs, whereas there were mild increases in sodium, chloride, and blood urea nitrogen in the other team. These opposing biochemical findings suggest physiologic changes associated with differences in hydration status, likely attributed to different dietary and hydration strategies used by the respective kennels.     

Creatine kinase in the dog: A review

In the dog, creatine kinase (CK) is mostly present in the skeletal muscles, myocardium, brain and intestine. The MM isoenzyme predominates in muscles and myocardium. In plasma, reference values depend on the technique used and CK-MB accounts for about 30–45% of total CK activity. Sex has no influence on plasma CK activity, which is higher in young dogs than in adults. Plasma CK is elevated after physical exercise. After its release from the cells, CK reaches the plasma mostly via the lymphatic route and then remains in the plasma compartment. It is rapidly cleared with a half-life of about 2 hours. Muscle diseases are the main source of plasma CK elevations: inherited myopathies, malignant hyperthermia, hypothyroidism, vitamin E-selenium deficiency, prolonged decubitus, intramuscular injections, surgery, etc. Plasma CK is also increased in experimental myocardial infarction, for which the dog is an interesting model, allowing quantification of the damage by measuring the total CK activity released.Abbreviations ADP adenosine diphosphate - ATP adenosine triphosphate - CK creatine kinase - DGKC Deutsche Gesellschaft für klinische Chemie - IM intramuscular - IV intravenous - K _m Michaelis constant - poly(A) polyadenylate - RNA ribonucleic acid - mRNA messenger RNA