Alpha 2 Adrenergic Receptors in Hyperplastic Human Prostate: Identification and Characterization Using [ 3 H] Rauwolscine

Abstract

[³H] Rauwolscine ([³H]Ra), a selective ligand for the alpha₂ adrenergic receptor, was used to identify and characterize alpha₂ adrenergic receptors in prostate glands of men with benign prostatic hyperplasia. Specific binding of [³H]Ra to prostatic tissue homogenates was rapid and readily reversible by addition of excess unlabelled phentolamine. Scatchard analysis of saturation experiments demonstrates a single, saturable class of high affinity binding sites (B_max = 0.31 ± 0.04 fmol./μg. DNA, K_d = 0.9 ± 0.11 nM.). The relative potency of alpha adrenergic drugs (clonidine, alphamethylnorepinephrine and prazosin) in competing for [³H]Ra binding sites was consistent with the order predicted for an alpha₂ subtype. The role of alpha₂ adrenergic receptors in normal prostatic function and in men with bladder outlet obstruction secondary to BPH requires further investigation.