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 (10^-5M) stimulated adenylyl cyclase activity by about two-fold, and the isoproterenol response was increased 1.8-fold after prolonged (48 h) exposure to EGF (5 x 10^-10M). 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 three-fold after EGF treatment. Competition binding studies using 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.