Platelet aggregation by basement membrane - associated collagens

Abstract

Solutions of Type IV collagen (from bovine anterior lens capsules) or of Type V (from human placenta or bovine lung parenchyma) failed to aggregate platelets even when pretreated either by incubation at 37°C or by dialysis against 0.02M-Na 2HPO 4 at 4°C - procedures known to induce the formation of highly active fibrils (with a 67nm axial periodicity) in the case of the interstitial collagens. Intact lens capsule containing Type IV collagen in situ was also inactive. However dialysis of solutions of Type IV or V collagens (from human placenta) against ATP at acid pH yielded SLS aggregates that were able, like those of Type I collagen, to induce platelet aggregation. Furthermore, dialysis of a solution of Type V collagen (from human placenta) against physiological saline at 25°C yielded fibrils of 67nm periodicity that could also induce a platelet response. Dialysis of Type IV collagen from human placenta against 0.02M-Na 2HPO 4 also yielded active fibrils - in this case, non-striated. These results indicate that quaternary structure rather than molecular composition determines the ability of collagen to induce platelet aggregation and that the basement membrane-types of collagen can, under appropriate conditions in vitro , exhibit a configuration suitable for platelet activity.