Effect of temperature on platelet interaction with subendothelium exposed to flowing blood

Platelet interaction with subendothelium exposed to whole blood in an annular perfusion chamber was investigated at 37, 20 and 4 °C. Decrease in temperature causcd a significant decrease in the coverage of the subcndothclial surface by platelets as well as in the formation of platelet microthrombi. In contrast, the total percentage of platelets in their initial state of attachment (contact) was increased. The corresponding decrease in platelets spread onto the surface (adhesion) suggested that the transition reaction from platelet contact to adhesion was significantly diminished by the reduction in temperature. Results of aggregation experiments in platelet-rich plasma with adenosine diphosphate and collagen suspensions were consistent with a decreased adhesion reaction to collagen. Mass transfer theory was used to compare platelet deposition results at 37 and 20 °C and suggested on of the following: (1) a platelet diffusivity in whole blood which was significantly more sensitive to temperature than the diffusibility of molecular solutes or (2) a significant decrease in the rate of the platelet attachment reaction at 20 °C.