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Tannin Uncouples the ß-Adrenergic Receptor (ßar) from G Proteins

M.M. Cloutier, C.M. Schramm, L. Guernsey


Tannin, isolated from cotton bracts, inhibits chloride (Cl-) secretion and secondary water transport in airway epithelium. The mechanism for this inhibition was examined using bovine tracheal epithelial cells and 3H-dihydroalprenolol. Tannin (25 µg/ml) exposure rapidly desensitized airway cells to isoproterenol-stimulated cAMP release. This desensitization was due in part to tannin-induced decreases in ß-adrenergic receptor number at the cell surface and to uncoupling of the ß-adrenergic receptor from its stimulatory G protein. Long-term tannin exposure (24 hr) further desensitized the airway epithelium to isoproterenol and forskolin suggesting downregulation of the ß-adrenergic receptor/cAMP pathway by tannin. These studies provide further evidence for the role of tannin in the occupational lung disease, byssinosis.

Reprinted from Proceedings of the 1996 Beltwide Cotton Conferences pp. 327 - 330
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998