Studies on the Determination of Serum and Urinary Prostaglandins by Radioimmunoassay

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The determination of PGs concentration by RIA is often encountered by the problem of cross-reacting PG homologues, and of the facile interconversion among these homologues. We have made a slight modification of Jaffe's method utilizing a pretreatment technique consisted of the extraction by organic solvent and column chromatography on silicic acid.<BR>The specimen was defatted wtih n-hexane, followed by PGs extraction into a mixture of ethyl acetate -isopropanol- water (7:3:6, v/v/v). The extract was then applied onto the minicolumn packed with silicic acid. The eluent employed was a mixed solvent of benzene, ethyl acetate, and methanol in variable ratios. The PGs were eluted in the order of PG (A+B), PGE, and PGF, separately.<BR>The assays of PGs were performed by Clinical Assays' RIA kits, with the sensitivity of 20 pg/ml. Although the results of dilution test for urinary PGs have exhibited an excellent linearity, the serum PGs concentration showed falsely low values when the large specimen volume (over 1 ml) was employed. It seems to be due to the effect of nonspecific interference caused by the coexistent neutral lipids.<BR>Using this method, we examined the serum PGE concentrations in congenital heart diseases and significantly high PGE levels were observed in some cases of tetralogy of Fallot, mitral insufficiency, and so forth.