Immunoaffinity purification of 11-dehydro-thromboxane B2 from human urine and plasma for quantitative analysis by radioimmunoassay

11-Dehydro-thromboxane B2 is now considered to be a reliable parameter of thromboxane A2 formation in vivo. An immunoaffinity purification method was developed for radioimmunoassay of this compound contained in human urine and plasma. Monoclonal anti-11-dehydro-thromboxane B2 antibody was prepared and coupled to BrCN-activated Sepharose 4B. Human urine or plasma was applied to a disposable column of the immobilized antibody. After the column was washed with water, 11-dehydro-thromboxane B2 was eluted with methanol/water (95/5) with a recovery of more than 90%. The purified extract was subjected to a radioimmunoassay utilizing 11-3H]dehydro-thromboxane B2 methyl ester and the monoclonal anti-11-dehydro-thromboxane B2 antibody. The detection range of the assay was 10-600 fmol (IC50 = 90 fmol). The cross-reactivities of the antibody with thromboxane B2, 2,3-dinor-thromboxane B2, and other arachidonate metabolites were less than 0.05%. These compounds were efficiently separated from 11-dehydro-thromboxane B2 by the immunoaffinity purification. This procedure also allowed the separation of 11-dehydro-thromboxane B2 from unidentified urinary and plasma substances which interfered with the radioimmunoassay. Validity of the results obtained by the radioimmunoassay was confirmed by GC/MS employing selected ion monitoring for quantification.