Binding of 125I-CCK-8 and 125I-gastrin-I to dispersed chief cells from guinea-pig stomach.
In dispersed gastric chief cells from guinea-pig stomach, binding of iodinated cholecystokinin octapeptide (125I-CCK-8) was relatively slow, temperature-dependent, to a single class of binding sites and inhibited by various gastrin- and CCK-related agonists and receptor antagonists. Binding of iodinated gastrin-I (125I-gastrin-I) was moderately rapid, temperature-dependent, to a single class of binding sites, and inhibited by various gastrin and CCK-related agonists and receptor antagonists. Gastrin-I as well as C-terminal fragments of CCK containing from eight amino acids (CCK-8) to four amino acids (CCK-4) stimulated pepsinogen secretion and inhibited binding of 125I-CCK-8 and 125I-gastrin-I. In addition, each of five different receptor antagonists inhibited binding of 125I-CCK-8 and 125I-gastrin-I and inhibited pepsinogen secretion stimulated by CCK-8 or gastrin-I. With each of eight different agonists and with each of five different antagonists the value of IC50 for inhibition of binding of 125I-CCK-8 was not significantly different from the value of IC50 for inhibition of binding of 125I-gastrin-I, indicating that in gastric chief cells the sites to which 125I-CCK-8 binds are the same sites to which 125I-gastrin-I binds. With the agonists as well as with the antagonists, however, there was no consistent relationship between the ability of a particular agent to inhibit binding and its ability to modify pepsinogen secretion, indicating that in gastric chief cells the sites that bind 125I-CCK-8 and 125I-gastrin-I are not the receptors that mediate stimulation of pepsinogen secretion by CCK-8 or by gastrin-I.
Sutliff
V E
VE
Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD.
Cherner
J A
JA
Jensen
R T
RT
Gardner
J D
JD
D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D005753:Gastric Mucosa / Q000166:cytology / Q000378:metabolism*; D005755:Gastrins / Q000378:metabolism*; D006168:Guinea Pigs; D007457:Iodine Radioisotopes; D007700:Kinetics; D008297:Male; D008969:Molecular Sequence Data; D011949:Receptors, Cholecystokinin / Q000378:metabolism*; D012844:Sincalide / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology
D005755:Gastrins; D007457:Iodine Radioisotopes; D011949:Receptors, Cholecystokinin; C036227:gastrin I; D012844:Sincalide