Recognition by goby intestine of a somatostatin analog, SMS 201‐995

The caudal neurosecretory peptide urotensin II and its partial structural analog the hypothalamic and gastroenteropancreatic peptide somatostatin can be distinguished by the goby posterior intestine; urotensin II stimulates Na⁺ and Cl⁻ absorption whereas somatostatin is without effect. Sandostatin^R (Sandoz compound SMS 201‐995) is a partial structural analog of somatostatin, possessing the active core common to both urotensin II and somatostatin but lacking the C‐ and N‐terminal tails which apparently confer recognition in species specificity. SMS 201‐995 mimicked the effects of urotensin II, namely, increased net Cl⁻ absorption and decreased radio‐chloride backflux consistent with the observed increase in transepithelial resistance and the cellular depolarization typical of transport stimulation in this tissue. Speculation on the role of the tails in species‐specific recognition is supported by the nature of amino acid residue substitutions in urotensin II, somatostatin, and SMS 201‐995 and suggests the existence of multiple receptor types for this group of peptides.