ADSORPTION OF PROTEINS OUT OF PLASMA ONTO GLASS FROM A SEPARATED FLOW

Perturbations in the adsorption of plasma proteins caused by flow sepa ration were studied quantitatively. An instrument was constructed that causes flow to separate over approximately half the width of a standa rd microscope slide and the pattern of protein deposition in and near the separated flow was observed by staining the slide with black iron oxide. The slide was mounted at the edge of a Couette flow field estab lished between two concentric cylinders, the outer of which was rotati ng. The slide was located on the stationary, inner cylinder just downs tream of a rectangular bar that causes the flow to separate. After exp osure to dilute plasma injected upstream of the bar, the slide was rem oved and stained with oxide suspension. The resulting, visible pattern was scanned through a video camera and analyzed to yield relative val ues of stain density that could be quantified. The oxide patterns sugg est that proteins were deposited onto the slide less rapidly in and ju st downstream of the separated flow region than farther downstream. At a shear rate of 6.61 s(-1), corresponding to a velocity of 1.32 cm s( -1) 0.2 cm above the point of flow separation, overall amounts of adso rbed proteins increased with exposure time in the range 3-30 min with the exception of a period from 10 to 11 min when all data show a tempo rary decrease. In calibration experiments, oxide failed to adhere to s lides exposed to purified albumin but adhered copiously to slides expo sed to purified fibrinogen. These results suggest that the oxide patte rns following plasma exposure are attributable primarily to fibrinogen and that the temporary decrease in the separated flow experiments is attributable to the displacement of fibrinogen by a less stainable pro tein, conjecturally high molecular weight kininogen and factor XII. Th is study yields quantitative information confirming earlier findings t hat were less controlled and non-quantitative. It confirms the hypothe sis that the sequence of protein deposition from dilute plasma to glas s surfaces is delayed in regions of separated flow.