SENSITIVE RADIOIMMUNOASSAY FOR SOMATOSTATIN USING N‐[1251‐TYR‐SOMATOSTATIN AS LABELLED ANTIGEN

Abstract
SUMMARY: A sensitive radioimmunoassay for somatostatin using N‐[25I]‐Tyr‐somatostatin is described and compared with that using [125I]‐Tyr1‐somatostatin. The minimum detectable amount of somatostatin using N‐[1251]‐Tyr‐somatostatin as tracer was 0.1 to 0.5 pg, which is approximately 10‐fold lower than the lower detection limit of the RIA using [125I]‐Tyr1‐somatostatin. Moreover, it was found that the shelf‐life of N‐[1251]Tyr‐somatostatin was prolonged in comparison with labelled Tyr1‐somatostatin. Human pancreatic and gastric extracts displayed immunological similarity to synthetic somatostatin tetradecapeptide.