ChemInform Abstract: Establishment of Microanalysis of Prostaglandin Metabolites by GC/MS and Its Clinical Application

We established microdetermination methods of prostaglandin (PG) metabolites by GC-selected ion monitoring (GC-SIM) and applied them to the clinical investigations. At first the microdetermination of delta 17-6-keto-PGF1 alpha, a hydrolyzed metabolite of PGI2, is described. An authentic delta 17-6-keto-PGF1 alpha was prepared from eicosapentaenoic acid (EPA) incubated with a homogenate from the bovine aortic intima. [18O] delta 17-6-Keto-PGF1 alpha was synthesized to obtain an internal standard for GC-SIM of delta 17-6-keto-PGF1 alpha. A good linear response over the range of 10 pg-5 ng was demonstrated. Chromatographic conditions using a MP-65HT column presented nearly baseline separation of delta 17-6-keto-PGF1 alpha and 6-keto-PGF1 alpha. Furthermore, a monoclonal antibody against cis-3-hexen-1-ol was prepared and used to separate and/or concentrate delta 17-6-keto-PGF1 alpha in the human blood sera. Using the prepared immunoaffinity columns of this antibody, delta 17-6-keto-PGF1 alpha was clearly detected in the human blood sera by GC/MS analysis. We were able to detect delta 17-6-keto-PGF1 alpha of the amount ranging from 6 to 26 pg/ml in the human blood plasma. The present method can be applied to the determination of delta 17-6-keto-PGF1 alpha in the human urine and plasma. Diabetes mellitus induces platelet alterations such as hyperaggregation. Variations in PG production seem to be related to this phenomenon but the changes in PG levels remain unclear. So we microanalyzed the 11-dehydrothromboxane B2 (TXB2) and 2,3-dinor-6-keto-PGF1 alpha, which were stable metabolites of TXA2 and PGI2, in the urine and investigated the relationship between the thromboxane/prostacyclin (TX/PGI) ratio and diabetes mellitus. The TX/PGI ratio in the urine of diabetics was higher than that of healthy volunteers. In murine, the TX/PGI ratio of STZ-induced mice was also higher than that of non-induced mice. The ratio of db/db mice also increased with the progress of diabetes mellitus. Furthermore, we investigated the relationship between the retinal vein occlusion (RVO), a thrombotic disease in which the retinal vein is blocked by blood aggregations, and the TX/PGI ratio. The TX/PGI level in patients with the RVO, who were not combine diabetes, was significantly higher than that in healthy volunteers. One of the causes of the RVO may be due to the variation of thromboxane production. This GC-SIM method can be used to determine the TX/PGI ratio in the urine.