Factors influencing shear-induced platelet alterations: platelet lysis is independent of platelet aggregation and release

Abstract

To gain further insight into the mechanisms involved in fluid shear-induced platelet alterations, we examined conditions and factors that might affect shear-induced platelet reactions in human citrated platelet-rich plasma (C-PRP) under well-defined laminar flow conditions at shear stresses between 0 and 160 dyn/cm 2 using a Couette rotational viscometer. Prevention of excessive alkalinization of C-PRP during shear due to CO 2 loss did not appreciably affect shear-induced platelet aggregation (PAG), adenine nucleotide (AN) release or platelet lysis. Shear-induced PAG and AN release were significantly greater in C-PRP stored and sheared at 24°C as compared to C-PRP stored at 24°C or 37°C and sheared at 37°C whereas platelet lysis was not affected by temperature. When C-PRP was sheared in the presence of EDTA or EGTA, shear-induced PAG up to shear stresses of 80 dyn/cm 2 was almost completely suppressed whereas AN release and lysis were unaffected. Exposure of C-PRP to PGE 1 and theophylline before shear virtually abolished shear-induced PAG and AN release at shear stresses up to 80 dyn/cm 2 but had no demonstrable effect on shear-induced platelet lysis. These findings seem to indicate that ADP released from platelets by shear and extracellular Ca ++ or in the presence of PGE 1 and theophylline. These findings seem to indicate that the structural and biochemical changes associated with shear-induced PAG and release in our system do not predispose platelets to shear-induced lysis.