Collagen-induced platelet aggregation: evidence of several mechanisms for the induction of platelet release by collagen.

Platelet function studies in 10 patients with prolonged bleeding time and reversible ADP-induced aggregation show that two types of ‘aspirin-like’ defects exist. Platelet aggregation studies with two different commercial collagen preparations give different results. Arachidonate also distinguishes the release deficiency into two groups, correlating to the results with collagen. Experimental studies with blockade of the platelet prostaglandin synthesis by acetylsalicylic acid show that the collagen preparations differ in their ability to elicit a release reaction despite this blockade.