The cholecystokinin-B receptor antagonist L-740,093 produces an insurmountable antagonism of CCK-4 stimulated functional response in cells expressing the human CCK-B receptor.
A stable cell line expressing the human cholecystokinin-B receptor gene (hCCK-B.CHO) has been employed in an evaluation of the recently developed CCK-B receptor antagonist L-740,093. L-740,093 exhibited high affinity (IC50 0.49 nM) and selectivity (<50% displacement at CCK-A sites at 1 microM) for the human CCK-B receptor subtype as estimated from [125I]-CCK-8S displacement studies with membranes prepared from hCCK-B.CHO cells. The elevation of intracellular free Ca2+ in hCCK-B.CHO cells in response to stimulation with CCK-4 was used to evaluate the antagonist activity of L-740,093 in vitro. L-740,093 potently (IC50 5.4 nM) antagonized the 30 nM CCK-4-stimulated Ca2+ mobilization in hCCK-B.CHO cells. Further studies were performed to investigate the nature of the antagonist activity of L-740,093. When tested at 10 nM L-740,093 produced a modest rightward shift in the CCK-4 dose response curve, an effect which was accompanied by a small reduction (13%) in the maximum response to CCK-4. In the presence of 30 nM L-740,093 the maximum functional response to CCK-4 was further reduced by 45% indicating that L-740,093 behaves as an insurmountable antagonist of the human CCK-B receptor subtype.
Dunlop
J
J
Biochemistry Laboratory, Wyeth Research Ltd, Maidenhead, UK. Dunlopj@war.wryeth.com
Pass
I
I
Ennis
C
C
D000818:Animals; D001570:Benzodiazepinones / Q000494:pharmacology*; D016466:CHO Cells / Q000737:chemistry / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D003001:Cloning, Molecular; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression / Q000502:physiology; D006801:Humans; D007457:Iodine Radioisotopes; D010671:Phenylurea Compounds / Q000494:pharmacology*; D011869:Radioligand Assay; D043887:Receptor, Cholecystokinin B; D011949:Receptors, Cholecystokinin / Q000037:antagonists & inhibitors* / Q000235:genetics*; D013758:Tetragastrin / Q000494:pharmacology*
D001570:Benzodiazepinones; D007457:Iodine Radioisotopes; D010671:Phenylurea Compounds; D043887:Receptor, Cholecystokinin B; D011949:Receptors, Cholecystokinin; D013758:Tetragastrin; C090649:L 740093; D002118:Calcium