Erythrocyte alterations endurance exercise in horses.

The erythrocytes of 14 conditioned horses participating in a 157-km endurance ride (requiring 14-21 h) were examined before the ride, immediately upon entering the 44-91-, and 130-km rest stops, and at the finish. At the first rest stop (44 km), the mean erythrocyte count increased 41% (P less than 0.001), the mean hematocrit (Hct) increased 30% (P less than 0.001) and the mean hemoglobin (Hb) increased 33% ( P less than 0.001). Although subsequent mean erythrocyte counts, Hct, and Hb values remained significantly elevated above controls, the values decreased 9-9% from the 4-km values later in the ride. These changes suggest a lost of red cells mass during the prolonged exercise. Spiculated red blood cells that increased markedly in number during exercise were also observed in these conditioned horses. The appearance of an increased number of spiculated red cells with exercise was associated with corresponding changes in red cell indices.

Fibrinolytic activity without fibrinogenolysis during long-distance racing in horses.

Fourteen horses were studied during a 157-km endurance ride. Two humans who ran the 157 km were also evaluated at the finish. Fibrin monomer samples were examined by two-dimensional gel electrophoresis and sodium dodecyl sulfate polyacrylamide gel electrophoresis. Two major species of horse Beta-chain with higher molecular weights and different isoelectric mobilities than human beta-chain were observed. Horse alpha-chains had higher molecular weights than human alpha-chains but similar alpha-chain heterogeneities. Mean euglobulin lysis time (ELT) in the horses was accelerated to similar levels throughout the ride (52% of control at 44 km, P less than 0.01), but mean plasma clot lysis time (PCLT) decreased progressively during the ride (30% of control at finish, P less than 0.005). Similar values for ELTs and PCLTs were noted in the runners and horses at the finish. Although fibrinolytic activity was accelerated for an extended period by the strenuous activity of this long-distance race, no evidence of increased carboxyl terminal degradation of the A alpha-chain was observed. This study suggests that prolonged physiological stimulation of the fibrinolytic enzyme (plasmin) system is not responsible for fibrinogen A alpha-chain heterogeneities observed in horses and humans. It further demonstrates the usefulness of horses as models for the study of exercise-induced fibrinolysis.