@entity2880 factor and fibronectin in the interaction of platelets in flowing blood with monomeric and fibrillar XXXX collagen types I and III.

@entity1 @entity2801 @entity1423 @entity73 @entity2881 @entity715 @entity2880
Platelet adhesion to monomeric collagen types I and III, which were purified from @entity1 umbilical arteries, was studied in a perfusion chamber under well defined flow conditions. For this purpose, glass coverslips were coated with 20-30 micrograms/cm2 of collagen types I and III by spraying a solution of these collagens with a retouching air brush. Platelet deposition increased with the time of perfusion. Adhesion to both collagen types was similar in the first 3 min, but @entity1423 occurred on collagen type III after 3 min due to @entity715 formation. Adhesion at a shear rate of 800 s-1 was strongly impaired with plasma of a @entity1 with @entity2880 or with fibronectin-free plasma. Addition of purified fibronectin to fibronectin-free plasma restored adhesion to the level obtained with normal plasma. Platelet deposition in normal plasma increased with increasing shear rates. Platelet deposition in VWD-plasma was normal at 490 s-1, but there was no increase at higher shear rates. Platelet deposition in fibronectin-free plasma was diminished at all shear rates studied from 490 to 1,300 s-1. Perfusion with a @entity1 albumin solution (HAS) to which purified @entity2880 factor complex ( @entity2801 - @entity2881 ) and fibronectin had been added gave similar platelet deposition as with normal plasma. Preincubation of collagen with @entity2801 - @entity2881 and perfusion with HAS containing fibronectin, or, conversely, preincubation with fibronectin and perfusion with HAS containing @entity2801 - @entity2881 , also resulted in adhesion similar to that observed in normal plasma. Similar adhesion was also observed after preincubation with both @entity2801 - @entity2881 and fibronectin and subsequent perfusion with HAS alone. Sequential preincubations with first @entity2801 - @entity2881 and then fibronectin, or with first fibronectin and then @entity2801 - @entity2881 followed by perfusion with HAS, also gave a similar adhesion as observed with normal plasma. These data indicate that platelet adhesion to monomeric collagen types I and III is dependent on both @entity2801 - @entity2881 and fibronectin. @entity2801 - @entity2881 is only required at relatively high shear rates; fibronectin also at relatively low shear rates. Their complementary role in platelet adhesion suggests separate binding sites for @entity2801 - @entity2881 and fibronectin on collagen. Platelet deposition on performed fibrils of collagen types I and III was also studied. Initial adhesion expressed as percentage surface coverage was similar to that found with monomeric collagen, but @entity715 formation was much enhanced. Adhesion on fibrillar collagen at 800 s(-1) was @entity73 and fibronectin-free plasma, and was restored by addition of purified fibronectin to fibronectin-free plasma. When perfusions were performed with HAS, only addition of @entity2801 - @entity2881 was required for optimal adhesion to fibrillar collagen; addition of fibronectin had no effect. These data are in contrast to the studies with monomeric collagens described above, in which the addition of both @entity2801 - @entity2881 and fibronectin was required. These data are also in contrast to the observation that in plasma both @entity2801 - @entity2881 and fibronectin are required for optimal adhesion to fibrillar collagen.
