High density of beta2-adrenoceptors in a human keratinocyte cell line with complete epidermal differentiation capacity (HaCaT)

Summary A non-tumorigenic keratinocyte cell line with complete epidermal differentiation capacity (HaCaT) was used in radioligand binding experiments to determine the number of beta-adrenoceptors. Intact cells were saturated with ³H-labelled (–)CGP-12177 (CGP), a hydrophilic non-selective beta-adrenergic antagonist as radioligand. In order to investigate the beta-adrenergic subtype selectivity, displacement experiments were performed with different antagonists and agonists. Binding of CGP to keratinocytes has been shown to be reversible and saturable and to have high affintiy (B_max=114.0±8.8 fmol/10⁷ cells with 6866 receptors/cell, K_D=0.095±0.017 nmol/l; n=11). Betaadrenergic antagonists inhibited binding yielding monophasic displacement curves. IC₅₀-values (nmol/l) were: propranolol (non-selective) 1.68; CGP-12177 (non-selective) 1.08; ICI 118,551 (beta₂-selective) 2.92; bisoprolol (beta₁-selective) 1230; and CGP-20712 (beta₁-selective) 24980. Agonists displaced CGP in the order isoprenaline> adrenaline>noradrenaline. We conclude that HaCaT cells express a high density of beta₂-adrenoceptors providing a good model system to study adrenergic receptor mechanisms under reproducible experimental conditions in keratinocytes.Part of this work was presented at the Meeting of the European Society of Dermatological Research (ESDR), Turin, June 9–12, 1990