BINDING OF BETA-ADRENERGIC RECEPTORS IN HUMAN SKIN

Radioligand-binding experiments were performed with crude membrane homogenates (CMH) from human skin in order to investigate the epidermal beta-adrenergic receptor (beta-AR) density. CMH were prepared from leftovers of split-thickness skin grafts by sequential homogenization and centrifugation procedures to yield essentially epidermal fragments. Saturation experiments with the non-selective beta-adrenoceptor antagonist (-)-[I-125]-iodocyanopindolol (ICYP) as radioligand showed saturable specific binding isotherms. Scatchard transformation of the data demonstrated high-affinity binding of ICYP to a single class of beta-AR (B(max) = 80 +/- 10 fmol/mg protein; K(D) = 8 pM +/- 0.9; n = 8). Beta-AR antagonists displaced ICYP in a monophasic displacement pattern. The IC50 values were (nmol/1) propranolol (non-selective) 24.8; ICI 118,551 (beta(2) selective) 14.7; CGP-12177 (non-selective) 28.9; bisoprolol (beta1 selective) 1500; CGP-20712A (beta1 selective) 8990. Beta-AR agonists displaced ICYP with a potency ranking isoprenaline > adrenaline > noradrenaline. We conclude that epidermal crude membrane homogenates prepared from human split-thickness skin contain a high population of beta2-adrenergic receptors. These receptors may be studied to further investigate the nature of human epidermal beta-adrenergic mechanisms.