Amino acids and collagen-induced platelet aggregation. Lack of effect of three amino acids that are elevated in homocystinuria.

Arterial thrombosis frequently occurs in homocystinuric children whose plasma levels of homocystine, homocysteine, and methionine are elevated. Since platelet aggregation is important in the pathogenesis of arterial thrombosis, we wondered whether the elevated concentrations of these amino acids might predispose to arterial thrombosis by enhancing platelet aggregation. Addition of the above amino acids to normal platelet-rich plasma to achieve concentrations within or above the range found in homocystinuric children had no effect on collagen-induced platelet aggregation. These data give no support to the hypothesis that the arterial thromboses of homocystinuric children are a result of enhancement of platelet aggregation by homocystine, homocysteine, or methionine.