The effects of epidermal growth factor (EGF) on the -adrenergic receptor-coupled adenylyl cyclase system were studied in a human salivary cell line (HSY). The -adrenergic agonist isoproterenol (10⁵ M) stimulated adenylyl cyclase activity by ~2-fold, and the isoproterenol response was increased 1.8-fold after prolonged (48 h) exposure to EGF (5 × 10¹⁰ M). In contrast, enzyme activation via stimulatory prostaglandin receptors and by agents acting on nonreceptor components of the adenylyl cyclase system was not enhanced by EGF. -Adrenergic receptor density, assessed by binding of the -adrenergic receptor antagonist ()-[¹²⁵I]iodopindolol, was increased threefold after EGF treatment. Competition binding studies with unlabeled antagonists selective for ₁- and ₂-adrenergic receptor subtypes indicated that the increase in ()-[¹²⁵I]iodopindolol binding sites induced by EGF reflected an increased number of ₂-adrenergic receptors. Likewise, Northern blot analysis of RNA from EGF-treated cells revealed selective induction of ₂-adrenergic receptor mRNA, which was blocked by the RNA synthesis inhibitor actinomycin D. The increase in -adrenergic receptor density produced by EGF was unaltered after phorbol ester-induced downregulation of protein kinase C (PKC). Enhancement of isoproterenol-responsive adenylyl cyclase activity and phosphorylation of mitogen-activated protein kinase (MAPK) by EGF were both blocked by the MAPK pathway inhibitor PD-98059. The results suggest that in HSY cells EGF enhances -adrenergic responsiveness by upregulating ₂-adrenergic receptor expression at the transcriptional level. Moreover, the stimulatory effect of EGF on ₂-adrenergic receptor signaling appears to be mediated by the MAPK pathway and independent of PKC activation.