Effects of Exercise on Plasma Haptoglobin Composition in Control and Splenectomized Thoroughbred Horses

In splenectomized Thoroughbred horses (Group S), the plasma haptoglobin (Hp) concentration was increased by the operation but thereafter significantly decreased to a lower level than before the surgery. The red cell haemolysis rate in a hypotonic salt solution and haemoglobin (Hb) binding Hp after exercise in Group S were significantly lower than in control horses (Group C). These results suggest that: 1) the spleen accelerates the fragility of the red cell membrane; 2) osmotic sensitive red cells are easy to haemolyze during exercise; and 3) the haemolysis during exercise increases the Hb-binding Hp level in plasma and then accelerates the synthesis of Hp in liver. Therefore, plasma Hp is a clinical indicator of red cell membrane fragility and haemolysis in a blood vessel during exercise.