ABSTRACT
Tannin, isolated from aqueous extracts of cotton, alters ion transport, PKC activity and arachidonic acid release and metabolism in airway epithelial cells. Tannin also inhibits the epinephrine and bradykinin induced rise in intracellular cAMP levels. Since binding of epinephrine and bradykinin are essential to their mechanism of action, we examined the effects of tannin on epinephrine and bradykinin binding to airway epithelial cells. Using Scatchard analysis, bradykinin binding demonstrates two binding sites with different affinities and binding site numbers. Tannin has no effect upon either the high or low affinity bradykinin binding site. In contrast, epinephrine binding demonstrates a single binding site. Tannin has no effect upon the dissociation constant for epinephrine but decreased epinephrine binding at 5 µ/ml tannin. These data demonstrate that tannin inhibits epinephrine binding but not bradykinin binding lo airway epithelial cells.
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