Optical Clearing Effect of Dextran on Human Platelet Suspensions

Abstract

THE optical density of platelet-rich citrated plasma or of platelet suspensions has been seen to decrease irreversibly on the addition of a solution of dextran¹. This decrease is biphasic, consisting of an immediate optical clearing effect independent of the molecular weight of the dextran fraction but related to its final concentration, and a delayed effect affected by molecular weight². Because certain dextran fractions induce aggregation of human platelets¹, it was at first assumed that the decrease in optical density of platelet-rich citrated plasma was caused by aggregation¹. Only the delayed changes in optical density, however, seemed to correspond to the degree of platelet aggregation evaluated microscopically after the addition of dextran². The immediate optical clearing effect of dextran has been further examined with a turbidimetric method and re-interpreted in the light of additional work on the optical properties of dextran.