ABSTRACT
In airway epithelial cells, tannin, isolated from cotton bracts, inhibits chloride secretion, decreases $-adrenergic receptor number, uncouples the $-adrenergic receptor from its stimulatory G protein and desensitizes the airway epithelium to $-agonists. We examined the effect of tannin on airway membrane protein phosphorylation, especially phosphorylation of the $-adrenergic receptor as a mechanism of rapid desensitization. Using bovine tracheal epithelial cells, gel electrophoresis and autoradiographic techniques, tannin promotes phosphorylation of 3 distinct membrane proteins, one of which is within the molecular weight range of the $-adrenergic receptor and is phosphorylated rapidly. The pattern and timing of the phosphorylation suggest a role for tannin stimulation of a $-adrenergic receptor kinase ($ARK) in tannin desensitization of airway epithelial cells.
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