The induction of the α-1-adrenoceptor signal transduction system on human melanocytes

Human melanocytes established in MCDB‐153 culture medium do not express α1‐, β1‐, β‐2 adrenoceptors without extracellular stimulation. The addition of 50×10−9 M norepinephrine to the medium causes a time‐dependent induction of α‐1‐adrenoceptors with 4.278 receptors/melanocyte after 24 h. Under the same experimental conditions, the dendricity of melanocytes as well as melanogenesis was unaffected over 60 h. Since keralinocytes hold the full capacity for catecholamine biosynthesis but melanocytes lack this system, the secretion of catecholamines from keratinocytes appears to be of critical importance to the α‐1‐adrenoceptor in melanocytes, underlining the symbiosis of both cells in the epidermal unit.