Effects of tannins from different sources on airway epithelial and platelet function.

The uniqueness of tannin isolated from aqueous extracts of cotton bracts (CBE) on the electrophysiological and ion transport properties of the canine tracheal epithelium and on 5-hydroxytryptamine (5-HT) release from platelets was investigated. The effect of CBE from Deltapine 41 cotton picked before (green, containing high-concentration, high-molecular-weight tannin) and after (brown, containing low-concentration, low-molecular-weight tannin) senescence and Darjeeling tea extracts and tannin isolated from Darjeeling tea were compared to the effects of Acala SJ-2 CBE and Acala SJ-2 tannin. Green Deltapine 41 CBE was similar to Acala SJ-2 CBE in decreasing short-circuit current (Isc) and net chloride secretion and in producing a dose-response release of 5-HT from platelets. Both Green and Brown Deltapine 41 CBE altered the paracellular pathway, but were less potent than Acala SJ-2 CBE. Brown Deltapine 41 CBE stimulated chloride transport in the airway epithelium and did not produce 5-HT release from human platelets. Darjeeling tea and tea tannin increased Isc and net chloride secretion and caused 5-HT release from platelets only at high concentrations. These studies demonstrate that all tannins are not alike; they suggest that molecular weight and concentration may be important for tannin activity and that the tannin in cotton bracts extract may be unique to cotton in its effect on the airway epithelium and on platelets.