Tannin is the major agent present in cotton mill dust responsible for human platelet 5-hydroxytryptamine secretion and thromboxane formation

Aqueous extracts of cotton mill dust were examined for their ability to activate washed human platelets as indicated both by the secretion of 5-hydroxytryptamine and the generation of thromboxane A₂. The cotton dust extract promoted 5-hydroxytryptamine secretion in a dose-dependent manner. When expressed in terms of its tannin concentration, the dose curve for cotton dust extract was identical to that obtained with purified tannin. Cotton dust extract also promoted the generation of low levels of thromboxane A₂. Fractionation of the extract by Amicon ultrafiltration into a > 10,000 MW fraction and a < 10,000 MW fraction revealed that the < 10,000 MW fraction contained an inhibitor of the thromboxane assay. The dose-response curve for thromboxane A₂ generation mediated by the > 10,000 MW cotton dust extract fraction was indistinguishable from that of purified tannin. Thus, 2 criteria show that platelet activation by cotton mill dust appears due to the tannin present in the dust.