Human Biochemistry Volume 2 - Murray R. 1993

Biochemistry of Intracellular and Intercellular Communication
Gastrointestinal Hormones
Background

Endocrinology as a science began with the Discovery of the first gastrointestinal hormone. In 1902, Bayliss and Starling introduced Hydrochloric acid into a denervated loop of a dog's jejunum and observed an increase in pancreatic fluid secretion. Intravenous injection of HCl did not produce this effect, but it was successfully reproduced by intravenous administration of an Histology/2.html">EXTRACT FROM THE jejunal mucosa. The authors concluded that this effect was mediated by "secretin," which is released upon stimulation of the upper intestine and carried via the bloodstream to the Pancreas, where it exerts its action. Bayliss and Starling were the first to use the term "hormone," and secretin turned out to be the first hormone with a defined physiological function.

Although secretin activity was discovered in 1902, it took a full 60 years to identify its chemical Structure. During this time, many "new" Hormones were discovered, their Amino acid sequences deciphered, and their synthesis achieved—often taking only a few years (e.g., Calcitonin; see Ch. 47). The reasons for the 60-year delay in deciphering secretin's chemical nature are now clear. Families of closely related Gastrointestinal Peptides share a great deal in common regarding their chemical structure and biological Functions, with most of these peptides existing in multiple forms. Methods for their Separation have been developed only recently.