EFFECT OF GENISTEIN ON AMYLASE RELEASE AND PROTEIN-TYROSINE PHOSPHORYLATION IN PAROTID ACINAR-CELLS

We evaluated the role of protein tyrosine phosphorylation in amylase e xocytosis from parotid acinar cells by using genistein, a tyrosine kin ase inhibitor, Amylase release stimulated by isoproterenol was dose-de pendently inhibited by genistein. Genistein also inhibited the exocyto sis evoked by dibutyryl- or 8-chlorophenylthio-cAMP. Daidzein, a negat ive control agent of genistein, elicited no inhibitory effect. Isoprot erenol had dual effects on protein tyrosine phosphorylation; it increa sed the phosphorylation of 190- and 210-kDa proteins and decreased tha t of a 90-kDa one. The phosphorylation was dose-dependently inhibited by genistein but not by daidzein, These results suggest that protein t yrosine phosphorylation plays a role in the process of amylase exocyto sis from parotid acinar cells.