Characterization of the [3H]-desipramine binding site of the bovine adrenomedullary plasma membrane

Summary The specific (i.e. nisoxetine-sensitive) binding of ³H]desipramine was studied in membranes prepared from bovine adrenal medullae. (1) ³H]desipramine bound reversibly and with high affinity (K _D = 2.8 nmol/l) to a single class of non-interacting binding sites (Hill coefficient = 0.96); the maximal number of binding sites (B_max) was 2.1 pmol/mg protein. (2) Binding of ³H]desipramine was dependent on Na⁺] and Cl^–]. Increasing the concentrations of these ions increased binding. (3) Substrates and inhibitors of the neuronal noradrenaline transport system (uptake,) inhibited binding of ³H]desipramine with a rank order of potency typical for an interaction with the uptake, carrier.The characteristics of ³H]desipramine binding remained essentially unchanged after solubilization of adrenomedullary membranes with the non-ionic detergent digitonin.The results indicate that the plasma membrane of bovine adreno-medulary cells is endowed with the neuronal uptake₁ transporter. Correspondence to: H. Bönisch