Development of a radioimmunoassay for the measurement of prostacyclin metabolites in unextracted plasma.

Levels of plasma 6-keto-prostaglandin F1 alpha (6-keto-PGF 1 alpha) measured in normal subjects by radioimmunoassay show wide variation. In an attempt to develop a sensitive, specific and reproducible assay for the measurement of the circulating metabolites of prostacyclin (PGI2) we examined the different variables involved in radioimmunoassay such as choice of buffer; incubation time and temperature; amount of radioisotope tracer added and the separation method. The method described gives good reproducibility and shows good correlation with in vivo and in vitro doses of PGI2.