Somatostatin binding sites in cytosolic fraction of rabbit intestinal mucosa: distribution throughout the intestinal tract.

Specific binding sites for somatostatin have been identified in cytosolic fraction of both small and large intestinal mucosa. The stoichiometric data suggested the presence of two classes of binding sites in each part of the intestine. The binding capacity varied depending on the segment considered (rectum greater than duodenum = jejunum greater than ileum, caecum and colon). However, the affinities of the binding sites were similar throughout the whole intestinal mucosa, with the exception of rectum which showed higher Kd values. The binding sites were shown to be highly specific for somatostatin since neuropeptides such as vasoactive intestinal peptide, neurotensin, substance P and Leu-enkephalin did not show any effect upon somatostatin binding.