Induction of Aggregation of Human Blood Platelets by Ultraviolet Light: Action Spectrum and Structural Changes

Exposure of washed human platelets to ultraviolet light is followed by platelet aggregation. The effect occurs at wavelengths between 302 and 225 mµ with a maximal response at 248 mµ, and the effect is greatly enhanced by the addition of fibrinogen. Platelets exposed to ultraviolet light show ultrastructural changes which can be induced independently of aggregation if the addition of fibrinogen is omitted.