Somatostatin, gastrin, and cholinergic muscarinic binding sites in rat gastric, duodenal, and jejunal mucosa

Clinical and experimental data indicate that the concentration of gastrin-I and somatostatin binding sites in human and rat gastric and duodenal mucosa may be changed in several pathologic conditions, including human peptic ulcer and cancer diseases. There are no data, however, indicating the distribution of receptor binding sites in the normal upper gastrointestinal tract. We studied the regional distribution of somatostatin-14, gastrin-I, and cholinergic muscarinic binding sites in membrane preparations from rat gastric corporeal and antral mucosa and in mucosa obtained from the duodenum and jejunum. The corporeal mucosa contained the most high-affinity gastrin binding sites (Bmax = 39.1 +/- 6.5 fmol/mg protein; Kd = 1.1 +/- 0.4 nM). The antral mucosa contained the most somatostatin and cholinergic muscarinic binding sites (Bmax = 65.7 +/- 6.6 fmol/mg protein and 460.3 +/- 101.8 fmol/mg protein, respectively). The duodenal and jejunal mucosal membranes contained somatostatin, gastrin, and cholinergic muscarinic binding sites in decreasing concentrations. Concentrations of binding sites are characteristic for particular gut regions and may help in analyzing their abnormalities.