Abstract

To investigate the hypothesis that diminished endothelial fibrinolysis is present in sickle cell (SS) disease plasma, tissue type plasminogen activator (t-PA) antigen titres were measured before and after a standard stimulus of endothelial t-PA release (venous occlusion of the arm), and plasma t-PA activities after venous occlusion in 33 subjects with SS disease and in 32 healthy subjects. Mean plasma t-PA antigen titres before and after venous occlusion, and mean plasma t-PA activities after venous occlusion did not differ significantly between SS patients and normal subjects. No significant differences in mean t-PA antigen and activity were observed between samples taken from inpatients being treated for acute pain crisis (18 subjects, 30 samples) and samples taken from subjects in the steady state (23 subjects, 26 samples). No consistent differences were seen between painful crisis and steady state samples in eight SS patients studied while in crisis and in the steady state. No correlation was observed between any fibrinolytic variable in SS patients and the overall severity of microvascular occlusive disease as measured by a standard scoring system. It is concluded that the capacity of endothelium to synthesise and release t-PA is not impaired in SS disease, and that excessive inhibition of released t-PA, leading to reduced t-PA activity in plasma is also not a feature of SS disease, either in the steady state or during painful crisis.