Recent advances in endocrinology / by A.T. Cameron.

  • Cameron, A. T. (Alexander Thomas), 1882-1947.
Date:
1933
Catalogue details

Licence: In copyright

Credit: Recent advances in endocrinology / by A.T. Cameron. Source: Wellcome Collection.

    355/402 (page 339)
    Secretin. The classical work of Bayliss and Starling in 1902, demonstrating the existence of secretin and its action in stimulating the outflow of pancreatic juice and bile, was confirmed at that time by numerous investigators. Little further work of importance on this compound was accom¬ plished, until in 1928 J. Mellanby isolated what appears to be almost a pure preparation of it (25). Pig’s duodenal mucosa was extracted with absolute alcohol, bile salts added to the extract, and then dilute acetic acid. The bile acids were precipitated and carried down secretin along with them. The wet precipitate was treated with absolute alcohol ; secretin passed into solution. It was precipitated by addition of excess of acetone, then dissolved in water, and finally precipitated by dilute acetic acid. Mellanby thus obtained an amorphous pale brown powder, which was of polypeptide and perhaps of protein nature. It was slightly soluble in water, and more readily soluble in dilute alkali, but insoluble in acetone, ether, and absolute alcohol (though soluble in aqueous alcohol). It was rapidly decomposed by pepsin, trypsin, and the tissue proteases. Injection into dogs of an amount which gave a concentra¬ tion in the blood of only one part in five millions gave a maximum flow of pancreatic juice. Bayliss and Starling put forward the theory that when acid reached the duodenum from the stomach an unknown pro¬ secretin in the gastric mucosa was changed to secretin which passed inwards to the capillaries of the mucosa and so to the general circulation. Mellanby believes the mechanism to be otherwise. Under normal digestive conditions the presence of food in the intestine leads to an outpouring of bile. Absorption of bile salts commences immediately and these carry with them preformed secretin to the general circulation. This evokes the secretion of pancreatic juice and of more bile, and so more secretin is absorbed. Such a theory seems more rational, and requires no explanation (as the earlier theory did) for the continued functioning of the pancreas in