The relative potency of the Crick-Harper-Raper unit and the GIH clinical unit of secretin.

A reinvestigation of the relationship between the Crick-Harper-Raper (CHR) and the GIH clinical units (CU) of secretin has been undertaken in anaesthetized cats with the knowledge that for some time before 1970 the CHR standard used by The Boots Company to assay secretin had lost some specific activity. One clinical unit of GIH secretin (batch no. 17421) is 3-8 times more potent than 1 Crick-Harper-Raper unit of restandardized Boots secretin (batch no. 142) in increasing the flow rate of pancreatic juice, and four times more potent in increasing the amount of bicarbonate.