Platelet-collagen interaction. The influence of native and modified collagen (Type I) on the aggregation of human platelets.

Type I collagen from calf skin, collagen modified by pepsin treatment, methylation, succinylation or deamidation, as well as the alpha-chains and cyanogen bromide peptides of the alpha1-chain were investigated with respect to their capacity to induce aggregation of human platelets. These preparations permitted an evaluation of the efficacy of the amino acid sequence, triple conformation,and various fibrillar structures in platelet aggregation. All collagens in dissolved in dissolved form (collagen dissolved at acid pH, pepsin-treated, methylated, deamidated, and succinylated collagen) induced platelet aggregation only after fibril formation. The arrangement of molecules within fibrils is of secondary importance. Modification of the side chains of amino acid residues affects primarily the formation of fibrils. The effect of these side chains on platelet aggregation is masked by the overwhelming potency of the fibrillar forms.