Adsorbed protein fibrin deposition

The thrombotic response (the time vs. platelet and fibrin deposition pattern) for uncoated PVC (shown in Figures 2 and 3) is a response to PVC that is coated with a complex mixture of proteins in the initial seconds of blood contact. Therefore, at least part of the thrombotic response on PVC is generated by a complex protein-coated surface composed of many proteins adsorbed in various conformations, including serum albumin, 7-globulin, fibrinogen, and fibronectin. However, these four proteins account for only 75% of the total protein in plasma and, therefore, significant amounts of other proteins not accounted for by our measurements may be adsorbed to the test surface. 

Figure 5. Transient fibrin deposition ( sem) on adsorbed protein substrates. Key A (SIL), uncoated Silastic (N = 5) (y-GLB), y-globulin on Silastic (N = 3) (FN), fibronectin on Silastic (N = 6) and A (a2M), a2-macroglobulin on Silastic (N =4).

The thrombotic response to uncoated PVC and to uncoated Silastic would be expected to be identical if thrombosis is surface nonspecific or if the surfaces initially adsorb the same proportion of the various plasma proteins that influence thrombosis. Comparisons of the responses of the uncoated surfaces (Figure 2 with 5 and 3 with 6) reveal that both the fibrin(ogen) and platelet deposition profiles on uncoated Silastic were significantly different than those on PVC. Fibrin(ogen) deposition proceeded at a slower rate on uncoated Silastic than on uncoated PVC, and peaked after 30 min of blood... 

Serum Albumin. The preadsorption of albumin on PVC resulted in a surface concentration of albumin that was 1.7 times (Table I) larger than the surface concentration that would adsorb in vivo to the uncoated PVC surface within 2 min of blood contact. However, this relatively small increase in surface coverage with the exclusion of other serum proteins resulted in a drastic decrease in the number of platelets and amount of fibrin(ogen) adhering to the surface at maximum deposition. 

---