Metabolism of thromboxane B2 in the isolated perfused rat kidney: mass spectrometric identification of urinary products

The metabolism of thromboxane B 2 (TXB 2 ), the stable breakdown product of thromboxane A 2 , has been studied in isolated perfused kidney preparations using a recirculating system. In a first experiment, TXB 2 was infused at a rate of 20 μg/kg per min. In a second experiment, a 1:1 mixture of TXB 2 and octadeuterated TXB 2 (0.4 μg/kg per min each) was infused. Urinary samples collected during the infusion of TXB 2 or vehicle were extracted on C18 cartridges and derivatized to methyl or pentafluorobenzyl ester, methyloxime, trimethylsilyl ether. Samples were analyzed by high-resolution gas chromatography-mass spectrometry in the electron impact and negative ion chemical ionization modes. Products of β-oxidation, reduction of the Δ5,6 double bond and dehydrogenation at C-11 (2,3-dinor-TXB 2 , 2,3-dinor-TXB 1 , 2,3,4,5-tetranor-TXB 1 and 11-dehydro-TXB 2 ) were identified in addition to unmetabolized TXB 2 . 2,3,4,5-tetranor-TXB 1 and 2, 3, dinor-TXB 1 were the most abundant metabolites.