Agonist binding promotes a guanine nucleotide reversible increase in the apparent size of the bovine anterior pituitary dopamine receptors.

摘要: Dopamine receptors, solubilized from bovine anterior pituitary membranes with the detergent digitonin, retained a typical dopaminergic specificity for binding of both agonists and antagonists. The affinities antagonists to soluble receptors are virtually identical those observed membrane-bound receptors. however, correspond form in having low affinity (De Lean, A., Kilpatrick, B. F., Caron, M. G. (1982) Mol. Pharmacol. 22, 290-297). Thus, after solubilization, agonist high interactions receptor their sensitivity modulation by guanine nucleotides lost. However, its can be preserved if prelabeled [3H]n-propylapomorphine prior solubilization. In order investigate molecular basis these changes properties binding, were characterized chromatographic procedures. Using exclusion pressure liquid chromatography, [3H]n-propylapomorphine-prelabeled elute as an apparent larger species than either unlabeled or antagonist [( 3H]spiroperidol)-pre-labeled Moreover, incubation pooled agonist-prelabeled peak effects decrease size such that upon rechromatography they position coincidental 3H-antagonist-pre-labeled peak. occupancy promotes formation nucleotide-sensitive which is presumably due association nucleotide regulatory protein.