Species variations of somatostatin concentrations and binding sites in jejunal mucosa

1. Somatostatin-like immunoreactivity (SLI) and specific binding of 125I-Tyr11-somatostatin were measured in jejunal mucosa of the mouse, rat, hamster, rabbit and guinea-pig. 2. The SLI concentrations in guinea-pig and rabbit were much greater than those in other rodents considered. 3. Somatostatin binding varied greatly with the species examined, the highest values being observed in cytosolic fraction of guinea-pig and rabbit jejunal mucosa, but the lowest ones in mouse. 4. The observed differences in somatostatin binding were not related to varying extents of degradation by the diverse cytosolic preparations studied. 5. The binding sites were highly specific for somatostatin in all rodent species studied. 6. There appears to be a direct relationship between somatostatin levels and somatostatin binding sites in jejunal mucosa when considering a variety of rodent species usually employed as laboratory animals.