Somatostatin-like Immunoreactivity in Human Peripheral Plasma Measured by Radioimmunoassay Following Affinity Chromatography

Somatostatin-like immunoreactivity (SLI) concentrations were determined in human peripheral plasma using affinity chromatography followed by radioimmunoassay. In normal subjects, fasting SLI ranged from 2.9 to 22.0 pg/ml with a mean ± SE value of 10.2 ± 2.1 pg/ml. In totally pancreatectomized or gastrectomized patients, fasting SLI levels were not different from the values in normal subjects. In patients with medullary thyroid carcinoma, fasting SLI ranged from 11.8 to 71.0 pg/ml with a mean of 29.3 ± 12.3 pg/ml, which was significantly higher than normal values (P < 0.01). Following meal ingestion, plasma SLI increased significantly in normal subjects from a basal level of 9.1 ± 2.1 pg/ml to a peak value of 15.4 ± 2.9 pg/ml (P < 0.02). These results indicate that radioimmunoassay combined with affinity chromatography provides an accurate method of measuring SLI in human plasma.