Prostacyclin production following in vitro mixing of normal with hemolytic-uremic-syndrome serum.

Serum from patients with the hemolytic-uremic syndrome (HUS) usually has a diminished ability to support the production of prostacyclin (prostaglandin [PG] I(2)). An impaired ability to produce this potent antiaggregatory substance could account for the thrombotic microangiopathy that is characteristic of the syndrome. We did in vitro mixing experiments to determine if adding normal serum in various concentrations would improve the ability of HUS serum to support PGI(2) production when incubated with cultured human endothelial cells. Mixing normal with HUS serum in a 1:2, 1:3, and 1:6 ratio generally enhanced the PGI(2)-supporting capacity of the HUS serum. Moreover, adding normal serum yielded a mixture whose supporting capacity was between the normal and the HUS serum's value, and the PGI(2)-supporting capacity could be predicted by calculating the weighted average value of the components of the mixture. There was a strong correlation between the calculated (predicted) and the actual experimental values (r = .95, P<.001).