Urinary excretion and origin of 11-dehydro-2,3-dinorthromboxane B2 in man

The in vivo biosynthesis of thromboxane B2 (TXB2) in man is currently evaluated by measuring urinary excretion of its major urinary metabolites, 11-dehydro-TXB2 and 2,3-dinor-TXB2. 11-Dehydro-2,3-dinor-TXB2, another prominent metabolite of exogenous TXB2 in man, has never been measured in human urine. We measured urinary 11-dehydro-2,3-dinor-TXB2 in parallel with 11-dehydro-TXB2 and 2,3-dinor-TXB2 by immunoaffinity extraction/gas chromatography-mass spectrometry in healthy non-smokers (n=12) and age-matched smokers (n=11). In non-smokers, urinary excretion of 11-dehydro-2,3-dinor-TXB2, 11-dehydro-TXB2 and 2,3-dinor-TXB2 was 29.7±11.1, 53.6±15.0 and 13.5±2.8 ng/h (mean±SD), respectively. In smokers, only urinary excretion of 2,3-dinor-TXB2 was significantly different (19.7±6.7 ng/h, p<0.01). Selective inhibition of platelet thromboxane biosynthesis by chronic low-dose aspirin (30 mg/day for 8 days, 4 subjects) comparably reduced platelet-derived metabolites and 11-dehydro-2,3-dinor-TXB2, suggesting that the latter also derives from platelets in healthy subjects.