GH(3) CELLS, AN ANTERIOR-PITUITARY CELL-LINE, EXPRESS CCK-B RECEPTORS

We found that GH-3 cells, a rat anterior pituitary tumor cell line, expressed a single class of high-affinity binding sites for radiolabeled cholecystokinin octapeptide (CCK-8) with a K(d) of 48 pM. The binding sites had high affinity for CCK-8, CCK-4, gastrin I, and L-365,260 (CCK-B antagonist), and had low affinity for devazepide (CCK-A antagonist), indicating that the binding sites are CCK-B receptors. GTP and its stable analogues inhibited radiolabeled CCK-8 binding to GH-3 cell membranes, suggesting a coupling of CCK-B receptors to a G-protein.