Characterization of cholecystokinin receptors in bullfrog (Rana catesbeiana) brain and pancreas

摘要: Abstract The binding of biologically active 125 I-Bolton-Hunter-CCK-33 to bullfrog brain and pancreatic membrane particles was characterized. Both tissues exhibited time-dependent, saturable, reversible, high affinity without evidence for cooperative interaction. CCK receptors resembled their mammalian counterparts in having acidic pH optima tracer a K d about 0.5 nM. However, the differed from that (1) membranes bound more per mg protein than did membranes, (2) both were relatively insensitive dibutyryl cGMP, (3) same general specificity toward variety gastrin peptides. For tissues, relative order receptor potency CCK-8 > caerulein = CCK-33 gastrin-17-II CCK-8-ns gastrin-17-I caerulein-ns gastrin-4 with sulfated peptides being 1000-fold potent nonsulfated analogs. Sulfated also potent, only 10-fold weaker CCK-8. Gastrin-4 20 000-fold interacting receptor. latter finding is sharp contrast We conclude pancreas contain similar probable physiological significance may represent an ancestral condition which two distinct present have evolved.