3H-Spiroperidol (Spiperone) Binding Sites in Rat Adrenal Glomerulosa Cells
3H-spiperone, a dopaminergic antagonist, was used to study binding sites in rat adrenal glomerulosa membrane. The equilibrium dissociation constant (Kd) and binding capacity for 3H-spiperone binding were 2.2 nM and 268 fmol/mg protein, respectively. Determination of the Kd by kinetic studies provided a value of 2.6 nM, which corresponded closely to the Kd estimated by equilibrium studies. In a study of the subcellular distribution of dopamine receptors in adrenal glomerulosa cells, 3H-spiperone binding activity at the interface of density 1.14 to 1.16 accounted for 60% of the total activity in all fractions. These dopaminergic binding sites in adrenal glomerulosa cells may modulate aldosterone secretion induced by antidopaminergic agents.
