Radioimmunoassay of somatostatin in human plasma

A radioimmunoassay procedure for determination of somatostatin immunoactivity in human plasma is described. Labelling of tyrosine-1-somatostatin is performed by chloramine T. Specific activity of the tracer is 1.34 mol iodine for 1 mol of somatostatin. The immunoreactivity is 85%. Antisera are produced in rabbits at a titre of 179 X 10(-12) mol somatostatin per ml antiserum. Human plasma is extracted by n-butanol/2 mol/l acetic acid. Recovery rate is 85-105%. The intra-assay CV varies from 12% to 1.7%, the inter-assay CV from 16% to 7.5%, depending on the concentration of somatostatin.