The measurement of plasma thromboxane B2 and the effect of smoking.

Plasma thromboxane B2 (TxB2) was measured by radioimmunoassay using an iodinated ligand following extraction and further purification by thin layer chromatography. Venous blood was sampled into a syringe containing the cyclooxygenase inhibitor meclofenamate. Normal levels, 15 pg/ml (s.d. = 8, n = 21), were lower than usually reported and measured values increased several fold over 20 min sampling from an indwelling needle. With appropriate sampling there was a statistically insignificant increase in plasma TxB2 after subjects smoked two cigarettes (n = 11). An average decrease occurred in a control group (n = 10) and the difference between groups was of borderline significance (P less than 0.05). Smoking did not change TxB2 production associated with platelet aggregation induced in vitro by collagen, whereas plasma adrenaline increased significantly. The results emphasize the importance of the technique of sampling and assay in the measurement of plasma TxB2.