Tannin mediated alveolar macrophage protein phosphorylation

Experiments were designed to determine if cotton bract tannin, a component of cotton mill dust, would promote the phosphorylation of alveolar macrophage proteins in doses potentially achievable in vivo. Rabbit alveolar macrophages were loaded with 32PO4 and challenged with various doses of tannin for time periods ranging from two seconds to 120 minutes. Changes in protein phosphorylation began after two seconds and were maximal at five to fifteen minutes. Dose response studies using an exposure time of one hour showed phosphorylation changes began at 1 micrograms/mL and were maximal at 10 to 30 micrograms/mL. Phosphorylation changes were similar to but not identical to those induced by the protein kinase C activator, phorbol myristate acetate (PMA). Calcium ionophore, A-23187 had no clear effect either alone or in conjunction with PMA. These results indicate that cotton bract tannin is able to rapidly promote protein phosphorylation of alveolar macrophages at doses potentially achievable in vivo. Other mechanisms in addition to those of protein kinase C appear to be involved in this protein phosphorylation process.