Receptors for gastrin on gastric carcinoid tumor membrane of Mastomys natalensis.
Specific binding sites for human gastrin I (gastrin) were identified in a crude membrane preparation from the gastric carcinoid tumor of Mastomys (Praomys) natalensis. The binding of 125I-gastrin to the carcinoid tumor membrane was saturable, and Scatchard analysis of the data revealed a single class of binding site with a dissociation constant of 139.2 pM and a maximal binding capacity of 23.5 fmol/mg protein. Gastrin and CCK8 equipotently and dose-dependently displaced the binding of 125I-gastrin to the membrane. GTP but not ATP decreased 125I-gastrin binding to the membrane, and removal of Mg2+ attenuated this inhibitory action of GTP. The GTP-induced reduction of 125I-gastrin binding was found to be due to a decrease in binding affinity without a change in binding capacity. These results clearly indicate the presence of specific binding sites for gastrin, probably coupled to guanine nucleotide-binding protein, in the carcinoid tumor membrane of Mastomys, and suggest that gastrin has possible biological actions on these tumors.
Chiba
T
T
Department of Medicine, Kobe University School of Medicine, Japan.
Kinoshita
Y
Y
Morishita
T
T
Nakata
H
H
Nakamura
A
A
Hosoda
S
S
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002276:Carcinoid Tumor / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D005260:Female; D005755:Gastrins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D009115:Muridae; D011949:Receptors, Cholecystokinin / Q000032:analysis* / Q000187:drug effects; D013274:Stomach Neoplasms / Q000737:chemistry / Q000378:metabolism*
D005755:Gastrins; D011949:Receptors, Cholecystokinin; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate