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.