Postnatal development of somatostatin levels and its binding sites in rabbit gastric mucosa

Using a specific radioimmunoassay technique, we have determined somatostatin-like immunoreactivity (SLI) in acid extracts of gastric (fundic and antral) mucosa as well as the specific binding of 125I-Tyr11-somatostatin to cytosol of the stomach of 0 to 150 days postnatal rabbits. The levels of somatostatin in both fundus and antrum decreased from birth up to day 5 followed by a sharp increase from 5 to 10 days, then decreased progressively until day 35. After this age, the somatostatin concentration remained relatively stable. The number of specific somatostatin binding sites of both high- and low-affinity increased gradually (without changes in the affinity values) with the development of rabbits, reaching the adult level by 35 days. However, there was an apparent lack of high-affinity sites immediately after birth (day 0). The somatostatin binding sites had characteristics identical with those found in adult animals with regard to their respective specific ligands.