GH3 cells, an anterior pituitary cell line, express CCK-B receptors

We found that GH3 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 Kd 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 GH3 cell membranes, suggesting a coupling of CCK-B receptors to a G-protein.