Radioimmunoassay for Somatostatin and Somatostatin-like Immunoreactivity in Human Plasma
A sensitive and specific radioimmunoassay for somatostatin is described. Anti-somatostatin sera was raised in rabbits after immunization with somatostatin-BSA conjugates. Tyr1-somatostatin was iodinated by the chloramine-T method. In a conventional radioimmunoassay system, the antiserum was used at a final dilution of 1 : 700,000. The sensitivity of the assay was 2 pg/tube and within and between assay precisions as coefficients of variation were 8.2% (range 15-30 pg), and 5.9% (range 20- 50 pg) respectively. The recovery of added somatostatin to human plasma was 51 ± 6.8% (Mean ± S. D.), using the acetone extraction method. The mean plasma immunoreactive somatostatin level among 10 healthy subjects was 10.4 ± 4.8 pg/ml at fasting, and plasma somatostatin-like immunoreactivity(SLI) increased significantly to a peak value of 16.2 ± 7.3 pg/ml 60 minutes after a mixed meal.