Identification of the major urinary metabolite of thromboxane B2 in the monkey

Thromboxane B2 (TxB2) was biosynthesized from prostaglandin endoperoxides (PGG2, PGH2) using guinea pig lung microsomes and infused into an unanesthetized monkey. Urine was collected and TxB2 metabolites were isolated by reversed phase partition chromatography and high performance liquid chromatography. A major metabolite (TxB2-M) was found to be excreted in greater than two-fold abundance relative to other metabolites. Its structure was determined by gas chromatography-mass spectrometry to be dinor-thromboxane B2. In vitro incubation of TxB2 with rat liver mitochondria yielded a C18 derivative with a mass spectrum identical to that of TxB2-M, substantiating that the major urinary metabolite of TxB2 in the monkey is a product of a single step of beta-oxidation.