Decrease of Platelet Aggregating Activity of Soluble Human Collagen Fractions during Ageing

Summary

Human collagen fractions of different solubility were prepared from aorta and skin homogenate using a differential centrifugation technique. All fractions of collagen aggregated platelets. The specific platelet aggregating activities were calculated as minimal hydroxyproline concentrations (MHC) causing platelet aggregation. The specific platelet aggregating activity was the highest in the soluble collagen fraction of young human subjects and then it decreased considerably (500 times on the average) during ageing. The specific platelet aggregating activity of young insoluble collagen was lower but it decreased less significantly during ageing. The changes in hexoses and hexosamines content of various collagen fractions did not appear to be relevant as regards platelet aggregating activity. It has been postulated that the masking of free amino groups in aged collagen following cross-links formation may be responsible, at least in part, for the loss of platelet aggregating activity of this protein.

^*) Present address: Vascular Laboratory, Lemuel Shattuck Hospital, Tufts University School of Medicine, Boston, Massachusetts 02130.

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