THE ASSAY OF SECRETIN IN THE RAT

Abstract

SUMMARY Some characteristics of the pancreas of the rat relevant to the assay of secretin are described, including mean basal flow rate and output of bicarbonate, minute-by-minute changes in rate of flow after different doses of secretin, dose—response relationships, and quantitative differences between the sexes. The coefficient of variation for a single determination of secretin was found to be 15·6%. Highly active secretin had no ecbolic effect, but pure cholecystokininpancreozymin (CCK-PZ) had a strong hydrelatic action. It is therefore formally impossible to assay secretin accurately in the presence of unknown amounts of CCK-PZ. This limitation applied to the cat also. Possible remedies are discussed. Crude preparations of secretin hydrochloride of very low potency which have been used as standards since 1955 appear to have suffered no loss of activity over several years. The value of the Hammarsten Cat Unit and of the Clinical Unit which is based on it seems to be substantially different in 1967, compared with earlier values, when assayed in the rat.