Growth and stability of thrombi in flowing citrated blood: assessment of platelet-surface interactions with...

The differential quantitation of platelet deposition in perfusion studies is a major problem. We report on methods to prepare semithin sections of platelet deposits on collagen coated on glass and plastic cover slips, to study growth and stability of thrombi in three dimensions, and the development of a computer-assisted differential quantitation of platelet-collagen interactions. The interactions were quantified as percentage of the surface covered with platelets (platelet adhesion), thrombus height, thrombus density and thrombus area per unit sectional length, respectively. Cover slips coated with fibrillar equine collagen in parallel-plate perfusion chambers were exposed to flowing citrated blood at shear rates ranging from 200 to 2,600 s-1. Thrombi, partially enmeshed in the collagen meshwork, prevailed on the surface at all shear rates. Maximal platelet adhesion and thrombus density were seen at greater than 5 micrograms/cm2 collagen, while thrombus area and height were maximal at greater than 10 micrograms/cm2. The volume of the thrombi appeared correlated to the number of deposited platelets (r = 0.92). En face preparations showed deposits of platelet islands which grew in diameter with time, particularly in the direction of the blood flow, becoming progressively confluent. Sections cut parallel to the direction of the blood stream indicated that this growth pattern was at least partially caused by thrombi bent in the direction of the blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)