Abstract
An assay method for secretin in crude preparations containing unknown amounts of pancreozymin has been developed, using rats. For several hours after urethan injection there was a marked fall in the volume of pancreatic juice correlated with the decrease of protein output of rat pancreas stimulated with secretin-pancreozymin mixture, then both reached steady-state levels. In this condition, where the sensitivity to pancreozymin was reduced, the pancreatic response was linearly related to the logarithm of the dose of crude or partially purified secretin in the ranges of 0.05-0.4 and 0.5-4.0 Crick, Harper and Raper (CHR) units, respectively. Within this range, the activity of crude secretin could be determined by four- and threepoint assay procedures with an error of 10 percent or less. The validity of the assay values for the crude preparations using the three-point design was confirmed by the recovery of secretin activity as highly purified secretin (free from pancreozymin) from the crude materials.
