[Prostacyclin stability in thrombotic thrombocytopenic purpura. Japan Working Group on TTP]

We investigated changes in prostacyclin stabilization activity of the plasma of 13 patients with TTP, by measurement of PGI2 inhibitory activity attenuation on normal platelet aggregation, induced by ADP (4 x 10(-5)M). PGI2 stabilizing activity of plasma was expressed as the half life (half time) in the time course of attenuation of the inhibitory effect of PGI2 on platelet aggregation. The half time was 16.7 +/- 5.8 min in the plasma of 10 healthy subjects. The half time in 10 plasma samples from patients in the acute state of TTP was significantly (p < 0.05) shorter than that of normal plasma. The half time become longer in 8 plasma samples after plasma exchange and increased to normal plasma level, in remission. There was no relationship between the concentration of plasma lipoprotein A1 and the half time of PGI2 stabization activity of plasma.