High susceptibility to ADP-induced platelet aggregation in mast cell-deficient W/W^v mice

Abstract

We used W/W^v mice genetically deficient in mast cells to clarify whether mast-cell-derived heparin may play a role to inhibit thrombus formation in living body or not. After small veins in mesentery of W/W^v or congenic +/+ mice were streched on to an inverted microscope, a micropipette filled with varying concentrations of ADP was set close to the outside of a vein by using micromanipulator; thrombus formation was directly examined under the microscope. The concentration of ADP necessary for thrombus formation in veins of W/W^v mice was significantly lower than the concentration in veins of +/+ mice. Furthermore, the concentration of ADP necessary for aggregation of platelets in platelet-rich plasma (PRP) was significantly lower in W/W^v mice than +/+ mice. The higher sensitivity of PRP of W/W^v mice is not attributed to the platelets but to the plasma, since platelets of +/+ mice suspended in platelet-poor plasma (PPP) of W/W^v mice were more sensitive to ADP than platelets of W/W^v mice suspended in PPP of +/+ mice. The present results⁴ show that plasma of W/W^v mice may lack some inhibitory factor (s) or contain promoting factor (s) for platelet aggregation.