Dopamine receptors on dispersed bovine anterior pituitary cells.
The dopamine antagonist [3H]-domperidone-[3H]-DOM-bound to a single class of high-affinity (Kd = 1.24 +/- 0.14 nM) and saturable receptors on dispersed bovine anterior pituitary (AP) cells. The binding of [3H]-DOM was stereoselective and reversible with agonists and antagonists. Dopamine competitions for [3H]-DOM binding modeled best for a single site consistent with an interaction with a homogeneous population of receptors. The mean number of specific binding sites labeled by [3H]-DOM was 53,000 per cell in dispersed AP cells consisting of 42% lactotrophs. Dispersed bovine AP cells attached to extracellular matrix within 3 h, and prolactin secretion from these cells was effectively inhibited by dopamine. Several observations suggested that [3H]-DOM-labeled receptors on dispersed bovine AP cells were restricted to the outer plasma membrane and not internalized. These included (1) the rapid and complete dissociation of specific [3H]-DOM binding; (2) the ability of treatment with acid or proteolytic enzymes to entirely remove specifically bound [3H]-DOM, and (3) the lack of effect of metabolic inhibitors on specific [3H]-DOM binding.
D000818:Animals; D001667:Binding, Competitive; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D004294:Domperidone / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism; D007124:Immunoenzyme Techniques; D010903:Pituitary Gland, Anterior / Q000032:analysis*; D011869:Radioligand Assay; D011954:Receptors, Dopamine / Q000032:analysis* / Q000378:metabolism
D011954:Receptors, Dopamine; D004294:Domperidone; D004298:Dopamine