URINARY-EXCRETION AND ORIGIN OF 11-DEHYDRO-2,3-DINOR-THROMBOXANE-B2 IN MAN

The in vivo biosynthesis of thromboxane B2 (TXB2) in man is currently evaluated by measuring urinary excretion of its major urinary metaboli tes, 11-dehydro-TXB2 and 2,3-dinor-TXB2. 11-Dehydro-2,3-dinor-TXB2, an other prominent metabolite of exogenous TXB2 in man, has never been me asured in human urine. We measured urinary 11-dehydro-2,3-dinor-TXB2 i n parallel with 11-dehydro-TXB2 and 2,3-dinor-TXB2 by immunoaffinity e xtraction/gas chromatography-mass spectrometry in healthy non-smokers (n=12) and age-matched smokers (n=11). In non-smokers, urinary excreti on of 11-dehydro-2,3-dinor-TXB2, 11-dehydro-TXB2 and 2,3-dinor-TXB2 wa s 29.7 +/- 11.1, 53.6 +/- 15.0 and 13.5 +/- 2.8 ng/h (mean +/- SD), re spectively. In smokers, only urinary excretion of 2,3-dinor-TXB2 was s ignificantly different (19.7 +/- 6.7 ng/h, p<0.01). Selective inhibiti on of platelet thromboxane biosynthesis by chronic low-dose aspirin (3 0 mg/day for 8 days, 4 subjects) comparably reduced platelet-derived m etabolites and 11-dehydro-2,3-dinor-TXB2, suggesting that the latter a lso derives from platelets in healthy subjects.