Abstract
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.
