Monomeric and polymeric collagen-induced platelet aggregation in citrated and heparinized platelet-rich plasma

The physical and chemical properties of Type I bovine collagens were studied in relation to their platelet aggregating activity in citrated and heparinized human platelet-rich plasmas (PRP). Despite close similarities in physical and chemical properties, significant differences were found in platelet aggregating potency between two monomeric atelocollagens. Skin atelocollagen was a potent and corneal atelocollagen was a very weak inducer of platelet aggregation in citrated and heparinized PRP. In a polymeric form, however, corneal atelocollagen was a stronger platelet aggregating agent than monomeric skin acid-soluble or atelocollagen. Removal of the telopeptides altered some of the characteristics of the platelet aggregation induced by monomeric skin collagen. The rate and maximum extent of aggregation were the same with skin acid-soluble (intact) and atelocollagens in either type of PRP, but the lag periods and aggregation times were longer in citrated and somewhat shorter in heparinized PRP with skin atelocollagen than with acid-soluble collagens. The possible mechanisms leading to the differences observed in platelet aggregating activity of collagens in different physical states and from different tissues, and their distinct platelet aggregation patterns in differently anticoagulated PRP, are discussed.