Use of plasma creatine kinase pharmacokinetics to estimate the amount of exercise-induced muscle damage in Beagles

Objective-To assess the effects of moderate exercise on plasma creatine kin ase (CK) pharmacokinetics and to estimate exercise-induced muscle damage in dogs. Animals-6 untrained adult Beagles. Procedure-The study was divided into 3 phases. In phase 1, dogs ran for 1 h our at a speed of 9 km/h, and samples were used to determine the area under the plasma CK activity versus time curve (AUC) Induced by exercise. In pha ses 2 and 3, pharmacokinetics of CK were calculated in dogs during exercise and at rest, respectively. Values for AUC and plasma clearance (CI) were u sed to estimate muscle damage. Results-At rest, values for CI, steady-state volume of distribution (Vdss), and mean retention time (MRT) were 0.32 +/- 0.02 ml/kg of body weight/min, 57 +/- 17.3 ml/kg, and 3.0 +/- 0.57 h, respectively. During exercise, Cl d ecreased significantly (0.26 +/- 0.03 ml/kg/min), MRT increased significant ly, (4.4 +/- 0.97 h), and Vdss remained unchanged. Peak of plasma CK activi ty (151 +/- 58.8 U/L) was observed 3 hours after completion of exercise. Es timated equivalent amount of muscle corresponding to the quantity of CK rel eased was 41 +/- 29.3 mg/kg. Conclusion and Clinical Relevance-These results revealed that exercise had a minor effect on CK disposition and that the equivalent amount of muscle d amaged by moderate exercise was negligible. This study illustrates the rele vance for use of the minimally invasive and quantitative pharmacokinetic ap proach when estimating muscle damage.