Radioimmunoassay of secretin in serum.

A radioimmunoassay for the measurement of immunoreactive secretin has been developed. The assay is specific and sensitive so that 2.8 fmol/ml can be measured. Basal secretin levels in man are generally undetectable and a protein-rich meal does not elicit a secretin response. However, the intraduodenal instillation of HCl leads to a prompt rise in circulating immunoreactive secretin and exogenous secretin administered intravenously is easily and accurately measured.