Counteraction of platelet activity at sites of laser-induced endothelial trauma.

The effects of dextran 70 (Mw 70,000; Macrodex), heparin, dipyridamole (Persantin), and prostaglandin E(1) on the behaviour of platelets were investigated at sites of endothelial trauma induced with a ruby biolaser in arterioles in the rabbit ear chamber. This technique has several advantages over previous methods of studying platelet activity.Dextran 70 (2 g./kg. body weight) caused a profound reduction in platelet activity four to six hours after its administration. Heparin (12 mg./kg. body weight) had no effect. The effect of dipyridamole (2.5 mg./kg. body weight) was profound immediately after its administration, but was transient. In preliminary experiments single intravenous injections of prostaglandin E(1) (25 and 125 mug./kg. body weight) had no detectable effect.