Secretin responses to feeding and acid load.

Secretin can be readily concentrated from 10 ml of plasma by adsorption to and elution from octadecylsilyl silica columns (C18 Sep-Pak cartridges). This method of concentration is more expedient than either ethanol extraction or adsorption to and elution from precipitated silica (QUSO G32) and permits detection of secretin in plasma at concentrations of 1 pg/ml or greater. Basal secretin in normal subjects was found to be less than 4 pg/ml of plasma. In response to an STM, plasma secretin increased on the average to twice the fasting level, but in response to an oral SAL, it generally increased about 10-fold.