Characterization of β-adrenergic receptors in cultured human trabecular cells and in human trabecular meshwork

The characterization of β-adrenergic receptors on cultured human trabecular cells and trabecular meshwork from human autopsy eyes was carried out by radioligand bindinb utilizing (¹²⁵I)-iodopindolol. In cultured cells, the observed binding of (¹²⁵I)-iodopindolol was of high affinity (K(d) = 43 pM) and saturable. Scatchard plots were linear and revealed a B(max) of 33 ± 7 fmol/mg of protein. Competition studies with a series of agonists and antagonists revealed that human trabecular cells contain a single class of β-adrenergic receptors of the β₂ subtype. Similarly, the IC₅₀ of ICI 89,406 (176 nM) in human trabecular meshwork from autopsy eyes supports the presence of β₂-adrenergic receptors in this tissue.