Silastic platelet deposition

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... 

Figure 6. Transient platelet deposition ( sem) on adsorbed protein substrates. Key A (S/L), uncoatea 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 =5).

None of the smooth surfaces prepared by the depositing of plasma polymer on the smooth surface of Silastic tubing showed detectable thrombus formation by gamma camera imaging. Therefore, they were evaluated by measurement of relative rates of platelet consumption. Table 35.7 shows the results obtained using the plasma polymers described previously [5]. 

The fibrin(ogen) and platelet response to y-globulin-coated Silastic was similar to that on y-globulin-coated PVC. On both surfaces the relative rate of deposition of fibrin(ogen) initially (Table I) was much less than that of the platelets. On Silastic, the preadsorbed y-globulin was 11 times more concentrated than the amount that would be adsorbed onto the uncoated surface. Not much embolization occurred during an experimental blood exposure time of 120 min. 

On Silastic, however, the thrombotic response to the fibronectin-coated surface was quite different than the response to the 7-globulin-coated surface. Initially, more fibrin(ogen) was deposited on the fibronectin-coated surface, whereas platelet adhesion was greatly diminished. At later times of blood contact, platelet adhesion to the fibronectin-coated surface increased... 

The embolization process on the fibronectin-coated PVC surface was quite different than the embolization process on fibronectin-coated Silastic. On fibronectin-coated PVC, 97% of the deposited thrombus [both platelets and fibrin(ogen)] were shed after 120 min of blood contact, while on fibronectin-coated Silastic only 75% of the deposited platelets and none of the fibrin(ogen) was released. This behavior is consistent with the observations shown in Figures 17 and 18 (fibronectin-coated PVC at 30 min and... 

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