Furosemide exhibits physicochemical properties similar to prostaglandins and interferes with their bioassay

The parallel pharmacological assay system has been of inestimable value in the identification and quantification of prostaglandins. A greater degree of specificity is conferred on the bioassay system by the preparative techniques of extraction and chromatography, for substances which might interfere with the assay of prostaglandins are usually eliminated by these procedures. It would be highly unlikely for a substance to survive the extraction procedure, to exhibit chromatographic properties similar to the prostaglandins and to interfere with their bioassay. We report here such an occurrence. Thus, furosemide not only survived the acidic lipid extraction, but, in addition, it exhibited chromatographic properties identical to those of the prostaglandins of the E series and finally, furosemide, at a dose which in and of itself was without effect on the assay tissues, inhibited the responses to prostaglandins. The quantification of prostaglandins by radioimmunoassay was, on the other hand, not altered by the presence of furosemide. This latter method appears to be the one of choice when interrelations between prostaglandins and furosemide are being examined.