Platelet thrombus induced in vivo by filtered light and fluorescent dye in mesenteric microvessels of the rat.

Intravascular platelet aggregation and subsequent thrombus formation were produced in the microvasculature by irradiation using filtered light from a mercury lamp in combination with the intravascular administration of a fluorescent dye. The effects of several factors, such as light intensity, dye concentration, and vessel diameter were examined in venules and arterioles of the rat mesentery with respect to the time required for the initiation of thrombus formation; the time to totally occlude the lumen; and the volume of the thrombus formed. It was found that the combined conditions of light intensity and dye concentration at specific values had a critical effect on the rate of platelet aggregation. In the arterioles and venules examined, the thrombus formation time was prolonged as a function of increasing vessel diameter. The time required for the initiation of thrombus formation and complete occlusion of the vessel lumen was greater in arterioles than in venules. This result may suggest the dependence of the kinetics of intravascular thrombus formation on blood flow conditions.