Pancreatic spasmolytic polypeptide (PSP): II. Radioimmunological determination of PSP in porcine tissues, plasma and pancreatic juice

A radioimmunoassay (RIA) for the determination of porcine Pancreatic Spasmolytic Polypeptide (PSP) has been developed. The antisera raised in rabbits were sensitive to 5 pgequiv. of PSP in a volume of 100 microliter. Immunoreactive PSP (IR-PSP) has been determined in extracts from 22 porcine organs. Pancreas was found to be the only organ containing substantial amounts of IR-PSP (0.1 mgequiv. IR-PSP/g wet weight). The fasting porcine plasma level of IR-PSP was about 10 ngequiv./ml, corresponding to 850 pM. The concentration of IR-PSP in porcine pancreatic juice varied from 0.2 mugequiv./ml in the fasting state to 46-116 mugequiv./ml after stimulation with pancreozymin or secretin. A linear correlation was found between the exocrine secretion of IR-PSP and total protein.