Presence of Ectopic β-Adrenergic Receptors on Human Adrenocortical Cortisol-Producing Adenomas*

A direct binding study of radioligand [3H]dihydroalprenolol (DHA), a potent β-adrenergic antagonist, was performed on the participate fractions of four adrenocortical adenomas (three cortisol-producing adenomas and one aldosterone-producing adenoma) and normal adrenal tissues. The effect of epinephrine on cortisol production was also evaluated in vitro from the cultured tumor cells from one cortisol-producing adenoma. Saturable binding of [3H]DHA to the tumor membranes was observed in two of three cortisol-producing adenomas, but not in the aldosterone-producing adenoma or in normal adrenal tissues. Scatchard analysis of equilibrium binding of [3H]DHArevealed a single class of binding sites on the tumor membranes; the apparent dissociation constant (Kd) was 1 nM in each, and the numbers of binding sites were 108 and 45 fmol/mg protein,respectively. Competition by adrenergic agents with [3H]DHA for binding sites on the membranes from one cortisol-producing adenoma revealed that (±)propranolol, a β-adrenerg...