Study of serum creatine kinase isoenzyme CKMB in endurance horses after prolonged physical exercise

Abstract

With the purpose of studying the influence of prolonged phyisical exercise causing myocardial lesion and disqualifying horses in endurance competitions, 87 blood samples were collected from adult Arabian and crossbred horses, to determine the serum concentration of the isoenzyme MB (CKMB), the serum activity of creatine kinase (CK), and the CKMB/CK index. Samples were divided as follows: C (control, n = 34): horses at rest, one day before competition; G1 (n = 24): horses which finished competitions; G2 (n = 14): horses disqualified during competitions by metabolic causes, and G3 (n = 15): horses disqualified during competitions after lameness was diagnosed. Median values obtained for CKMB, for groups C, G1, G2, and G3, were, respectively, 2.25; 2.95; 1.95, and 2.40 ng/mL; for CK activity, the results were 164.2; 1228.0; 840.0, and 581.0 in U/L at 30°C; and for CKMB/CK index, the results were 1.41; 0.21; 0.23, and 0.42%. There was mean positive correlation between distance and CKMB and CK, and negative correlation between distance and CKMB/CK index. It was concluded that endurance exercise does not cause significant increases in CKMB values, but in CK serum activity, indicating skeletal muscle injury. Horses disqualified by metabolic causes seem not to present myocardial injury involved in the cause of disqualification. It was not possible to verify the presence of exercise-induced cardiac injury in endurance horses and its relationship with metabolic causes of disqualification only by the utilization of CKMB as the only cardiac marker.