A textbook of biochemistry for students of medicine and science / A.T. Cameron.

  • Alexander Thomas Cameron
Date:
1942
Catalogue details

Licence: In copyright

Credit: A textbook of biochemistry for students of medicine and science / A.T. Cameron. Source: Wellcome Collection.

    67/398 (page 53)
    evidence that it has any other direct action Jhan this, although this limitation of its action to causation of glycogen. formation cannot be regarded as proved. Secretin is a hormone elaborated by cells in the mucous membrane of the upper part of the small intestine, the duodenum and (to a lesser extent) the jejunum. Bayliss and Starling showed in 1902 that if the nerve supply to an isolated loop of intestine were cut, and then a*cid was injected into the loop, a well-marked flow of pancreatic juice followed. Then they demonstrated that if the mucous membrane was scraped off a loop of jejunum of a dog, rubbed up with sand and 0-4 per cent, hydrochloric acid, then boiled to coagulate the protein content and filtered from this, the filtrate, when injected into a vein of this or another animal, produced within twenty seconds a copious flow of pancreatic juice. They named the essential constituent secretin, and assumed that a precursor, pro-s^cretin, is present in the cells of the mucus, a change of pH in the direction of acidity leading to the formation of the active compound. The presence of secretin has actually been demonstrated in the blood leaving a loop of intestine into which acid has been introduced. Its action is not limited to the pancreas ; the flow of bile is increased. The mode of action is not kliown. Secretin has been crystallised by Agren and Wilander, and shown to be a polypeptide with a molecular weight of about 5,000, and containing sulphur. The adrenal glands are, as their name suggests, two small glands adjacent to (the upper poles of) the kidneys. Each gland is composed of two entirely unlike tissues ; its interior portion, its medulla, is composed of tissue of nervous type ; the exterior and larger portion of each, its cortex, is composed of more typically glandular material. The adrenal medulla secretes adrenaline (or adrenine or epine- phrine]). This is a simple derivative of the amino-acid tyrosine, and is probably formed through the intermediate stage of tyramine. It is also closely related to the compound ephedrine, derived from the Chinese drug Ma Huang (Ephedra vulgaris). The formulae of these compounds are— H H H A A ° H A a A C /\ HC CH /\ HC CH /\ HC COH HC^JH HC CH II 1 HC CH HC CH II | HC CH \/ \/. \/ \/ C C C C CHa ch2 CHOH CHOH CH. COOH CH2 | ch2 ch.ch3 nh2 nh2 1 HN£H3 | HNCH, 3 * Tyrosine 'Tyramine Adrenine Ephedrine