Secretin in plasma: Ups and downs.

The establishment of a reliable radioimmunoassay for secretin in plasma enabled studies on the physiology of secretin. It was shown that secretin, i.e. the heptacosapeptide isolated by Jorpes and Mutt, is in fact responsible for the phenomena observed by Starling and Bayliss in 1902 when studying the stimulation of pancreatic bicarbonate secretion in response to duodenal acidification. Secretin is released in amounts considerably lower than anticipated, but these amounts are nevertheless sufficient to drive pancreatic and biliary secretion of bicarbonate. Whereas secretin in the fasting state is the most important stimulus to pancreatic secretion of water and bicarbonate, other hormones and nervous factors are essential for the majority of pancreatic postprandial secretion. [ABSTRACT FROM AUTHOR]